Know Your Natives – Ditch Stonecrop

Ditch stonecrop (Penthorum sedoides) of the ditch stonecrop (Penthoraceae) family is a short-lived, herbaceous perennial of wetlands. The genus name originates from the Greek words for “five” and “marker” in reference to the pentamerous (five-part) floral structure. The specific epithet translates to “resembling sedum,” also in reference to floral structure.* In the U.S., ditch stonecrop is the only species of Penthorum; a second species is known from Eurasia. Ditch stonecrop occurs throughout the eastern U.S. to eastern Texas, Nebraska, and eastern North Dakota. In Arkansas, it occurs statewide. Habitat preference is full to partially sunny sites with shallow, standing to slow-flowing water, where mucky soils remain wet in low-rainfall conditions, such as ditches, floodplain depressions, pond margins, and marshes.

Photo 1: In this wetland habitat, ditch stonecrop grows with arrowhead (Sagittaria platyphylla).

Young plants, growing during the summer months, have a single aerial stem above water as well as leafy basal branches that arise from submerged rhizomes. Basal branches, up to six inches long, remain parallel to the soil surface with ascending tips. White, string-like secondary roots descend from the main root and the basal branches. With plant maturity, these become dark and matted.

Photo 2: Display of young plants showing a single emergent erect stem with well-spread leaves and several submerged leafy basal branches. Rhizomes have a pointed lower tip, as identified by red arrow above center plant. Photo – November 8.
Photo 3: By raising this clump of muck, water drained off to expose the leaf-shrouded basal stems on these three plants, each with a single aerial stem. Photo – November 8.

Erect stems, 1 to 2+ feet tall at maturity, are terete, slightly ridged, and slightly zigzagged between the nodes (this more prominent on new growth). They are light green to pale red (in more sunny sites). Floral branches arise near the stem apex, each subtended by a leaf. Stem pubescence is sparse, coarse below and becoming finer distally. Inflorescence branches are glandular pubescent. An aerial stem apparently dies soon after it has produced fruit.

Plants that do not have submerged bases do not develop basal branches. If an upper portion of a stem becomes submerged, it develops basal-branch look-alikes.

Photo 4: These plants (foreground) have not developed the leafy basal branches because their bases are not submerged. Plants in mid-background are cardinal flowers (Lobelia cardinalis).

Stem leaves are alternate and lanceolate-elliptic, to 6-7 inches long and 1½ inches wide, the blade tapering to a pointed tip and base. Largest leaves occur mid-stem. Blades are glabrous and sessile to short-petiolate, with fine, mucronate (tipped) serrations along their margins. Alternate, tightly clustered leaves of basal branches are about 1 inch long and ½ inch wide. Lower leaves of the aerial stems drop-off as tips of the basal branches continue to grow.

Photo 5: The two outside leaves are aerial stem leaves with upper surface shown on left and lower surface on right. The basal branch, at center, has a basal-stem-leaf at its left (upper surface) and its right (lower surface). Large leaf on left is 6 inches long and 1½ inches wide.

The inflorescence develops over the summer months. It consists of 2-4 flower-bearing “arms,” 1-sided racemes (technically cymes), extending from the tip of the main stem and, often, 1-2 axillary floral branches immediately below. Flowering begins at the basal flower and extends distally as the racemes uncoil from their initial fiddlehead shape. The eventually straight, ascending and arching floral branches bear several to 15 flowers on minute (< ⅛ inch) pedicels. Floral branches may be up to 2 inches long and have few to 20+ flowers. Floral branches below the terminal racemes may be 1¾ inches long and may bear one to several lanceolate leaves that are to 1¼ inches long and ½ inch wide. Along with the dense glandular hairs on floral branches, noted above, tiny deeply serrated bracts occur. The inflorescence may become reddish with fruiting.

Photo 6: This group of plants is at the blooming stage. A plant may have several floral branches below the terminal inflorescence. The plant with the red asterisk appears to have three especially long floral branches. Photo – August 17.

Flowers have a bowl-shaped hypanthium or floral cup, which is to 3/16 inch across and ⅛ inch deep, bearing 5 triangular green sepals. The greenish-white flowers, typically lacking petals, have 5 (sometimes 6) pistils (ovary, style and stigma) united below and 10 stamens. The pistils are arranged in a central ring with the stamens both alternate and opposite to them. Each pistil comprises a single carpel. Each ovary has central placentation, a prominent post-like style (with a wide conical base), and a large convex stigma. At anthesis, styles are erect but flare outward in fruit, as the shiny greenish white stigmas become black.

Photo 7: In addition to the single flower that terminates the stem at the base of the inflorescence (partially hidden in photo), flowers extend in secund (1-sided) fashion along coiled arms. Convex stigmas terminate post-like styles. Note sepals, dense glandular pubescence, and tiny leaf-like bracts along the inflorescence axes. Photo – July 27.

Fruits retain the form of the flowers with the hypanthium, sepals, and 5 projecting styles persistent. The ⅛ inch long styles give the 5-carpellate fruits a prickly appearance. As fruits develop, the entire floral structure may become reddish, ultimately turning tan to dark brown at maturity. Seed dispersal occurs when the style with its conical base drops off a chamber to allow numerous tiny oblong (1/32 inch long) white seeds to drop away.

Photo 8: Fruiting capsules, which may become reddish, have a prickly appearance due to persistent styles and stigmas (black in photo). Flowers have a central “empty” disk that may aid with insect pollination. Photo – November 8.
Photo 9: This inflorescence arm (tip at lower left) has dried and the conical styles are starting to drop off (see capsule at base and 4th capsule from lower left). Several cap-like dropped styles are displayed above the arm, along with seeds. Squares = ¼ inch. Photo – October 16.

For a garden or natural area, ditch stonecrop needs a site that is continuously wet to occasionally flooded, such as a water garden, drainage, or pond margin. Plants would provide cover for water-based insects and amphibians. Ditch stonecrop is a good native plant for aquariums because of its leafy basal branches, which grow naturally submerged.

* Sedums are in the Stonecrop (Crassulaceae) family, in which ditch stonecrop was once included. There are four species of sedums known from the wild in Arkansas: the native Nuttall’s stonecrop (Sedum nuttallii), widow’s cross (Sedum pulchellum), and woodland stonecrop (Sedum ternatum), and the non-native yellow stonecrop (Sedum sarmentosum). All have succulent leaves.

Article and photographs by ANPS member Sid Vogelpohl

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Know Your Natives – Southern Prairie Aster

Southern prairie aster (Eurybia hemispherica) of the Aster or Sunflower (Asteraceae) family is a slender stemmed plant with spectacular, inch-wide, lavender composite flowerheads. The genus name is based on Greek words for “wide” and “few,” a reference to big-leaf aster (Eurybia macrophylla), most likely to the ligules of the ray flowers. The specific epithet derives from the Greek words for “half” and “sphere,” in reference to the involucre. Occurrence in the U.S. is primarily from eastern Texas and southeastern Kansas, east to southwestern Kentucky and the panhandle of Florida, excluding lowlands of the Mississippi River alluvial plain. In Arkansas, the species occurs nearly statewide, excluding some Mississippi Alluvial Plain and northern Ozark counties. Preferred habitat is sandy to rocky, mesic to dry soils of upland prairies and open woodlands.

Southern prairie aster is a long-lived herbaceous plant that forms loose clonal clumps. Plants have a short vertically oriented main root with many descending roots and shallow runners. Runners, originating from various levels of the main root, extend to 6 inches from the main root. Unlike roots, runners are modified stems, and are thus segmented at nodes, with each node subtended by a small fully clasping bract. One to several deciduous stems grow from the apexes of the main root and runners. Older portions of the main root and runners become reddish brown, while roots are light tan.

Photo 1: This plant has a vertical central root (¾ inch long) and several segmented runners. Runner extending to the left is 4½ inches long. In this mid-September photo, basal and cauline leaves (see below) have been lost.

The unbranched, mostly erect, wiry stems, to 20+ inches tall, are yellowish green to slightly reddish in sunlight. They are mostly glabrous, but may have short pubescence toward the inflorescence.

Photo 2: Plants have wiry unbranched stems topped with a single or several flowerheads. Photo – September 9.

Basal leaves, present in spring and fall, and cauline leaves have different shapes. Basal leaves may be spatulate with an acuminate apex to broadly lanceolate. They are flexible and glabrous except for the smooth margins which are minutely roughened.

Cauline leaves are alternate, stiff and ascending, lanceolate to linear, with an acuminate to obtuse apex and a narrowing base. They decrease in size from stem base (to 8 inches long and ¼ inch wide) toward the inflorescence (1½ inches long and ⅛ inch wide or smaller). The closely spaced leaves are clasping on the lower portion of the stem (base extending half-way around stem) to sessile along the upper portion. Leaves are a dull medium green above and a shiny light green below. While the lower leaf surface is glabrous, the upper surface and margins are roughened by minute hirsute pubescence. The leathery (coriaceous) leaves are up-folded along the midrib, which is slightly depressed above and prominently expressed beneath. Pinnate secondary venation is obscure. At the time of flowering, lower leaves tend to drop off. Tufts of small leaves (or small flowerheads) occur in leaf axils below the inflorescence, more apparent distally, but do not develop unless the stem above such a node is damaged.

Photo 3: Flexible basal leaves are spatulate to broadly lanceolate while the stiff cauline leaves are lanceolate to linear. Lower cauline leaves are clasping. Photo – September 2.

The inflorescence, with the bloom period extending from August into October, may be a single terminal flowerhead or a terminal flowerhead along with an additional 2-6 axillary flowerheads racemosely disposed immediately below. Flowerheads may also occur at the stem apex in a shortened corymb. Flowerheads are sessile or borne on peduncles to 3 inches long that may bear one to several scattered lanceolate leaf-like bracts. The hemispherical involucre is comprised of 50-60 phyllaries (bracts of the composite head) in 4 to 6 series. Involucres are to ½ inch long and 1 inch wide. The outer stout lanceolate phyllaries become elongate-triangular, smaller and thinner above. Phyllaries are spreading to ascending, with spiky mucronate tips, glabrous above and minutely hirsute beneath.

Photo 4: Four to six series of involucral bracts are mostly stout, but become shorter and weaker toward the center. Leaf like bracts may occur below the involucre.

Flowering sequence of racemes proceeds downward from the terminal flowerhead. The composite flowerheads consist of 20-35 pistillate (no stamens) ray florets and ± 50 perfect (with pistils and stamens) disk florets, flowering sequentially from the perimeter to the center of the disk. As heads approach anthesis, ligules of the ray florets are erect and disk florets are covered by the flattened pappus (long hairs attached to the ovaries). As heads develop, the light to dark lavender strap-like ligules expand to ½ inch long and become widely spread around the disk. The ¼-inch-long yellow disk florets have tubular corollas with five short-triangular erect lobes. Stamens have slender filaments and elongate anthers which join laterally to form a ring around the style. As the style elongates through the anther ring, it picks up the pollen and carries it to the surface of the disk where it is exposed to pollinating insects. The long stigma then divides (bifurcates), with the paired stigmatic surfaces slightly separating.

Photo 5: As flowerheads approach anthesis, disk florets are mostly obscured by the silky pappus. Peduncles often have leaf-like bracts below the 4 to 6 series of phyllaries. Photo – September 17.
Photo 6: Widely flared ligules are disposed in a single layer with occasional gaps and overlaps. Involucres have a hemispherical shape.
Photo 7: Pistillate ray florets and perfect disk florets are both fertile. Bifurcated stigmatic surfaces become slightly separated, touching at their tips.

With completion of flowering, the entire stem dries and the phyllaries loosen, with the eventual release of 1-seeded, strongly ribbed, indehiscent fruits (achenes). The ⅜-1 inch long, bullet-shaped, slightly flattened achenes are tipped with a ring of 20-30 rigid plumose hairs (pappus). The well-attached arched hairs provide lift for wind dispersal.

Photo 8: As stems die, seeds mature and pappus fluffs-up. Photo – October 29.
Photo 9: Achenes, equipped with a pappus of plumose hairs, are dispersed by wind. Squares = ¼ inch.

Southern prairie aster is a good selection for a native plant garden or natural area with mesic to dry soil. It is not aggressive but may form small colonies. With its narrow leaves and wiry stems, the plant will probably be unnoticed until it blooms. Flowerheads are large for an aster but occur in limited numbers.

An additional species of the genus which is known only historically from Arkansas (Benton County only) is big-leaf aster (Eurybia macrophylla), not observed in the state since 1926. Big-leaf aster has large heart-shaped leaves and flowerheads in open cymes. Southern prairie aster is easily distinguished from 22 other “asters” in the Symphyotrichum genus by the appearance of its leaves, stems and flowerheads.

Article and photographs by ANPS member Sid Vogelpohl

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Know Your Natives – Tall Thistle

Tall thistle (Cirsium altissimum) of the Aster, Sunflower or Composite (Asteraceae) family is a tall biennial thistle with weak spines and pink to lavender flower heads. The genus name derives from a Greek root for “swollen vein” in reference to past use of the plants to reduce swelling. The specific epithet is Latin for “tallest.” In the U.S., occurrence is concentrated in an area extending from eastern Oklahoma and Arkansas northward into Minnesota to western Pennsylvania, along with scattered populations from eastern Texas into western South Carolina. In Arkansas, tall thistle occurs statewide. Preferred habitats include prairies, woodlands, wood borders, and disturbed sites, on mesic, well-drained, sandy, rocky, and loamy soils.

Plants in their first year have a rosette of long-petiolate ascending elliptical leaves with minute pubescence overall and margins lined with minute spines. First year plants have long (to 6+ inches) slender taproots with a swollen segment along the lower portion. New growth for the second year begins as a rosette of rugose, ground-hugging leaves with long pubescence and stout marginal spines. Mature second year plants have shallow, sinewy, radiating roots as well as remnants of the first year’s tap root.

A second year plant, growing to a height of 5 ft (shady sites) to 10 ft (sunny sites), has straight, erect, hollow stems, with a cross-section to ⅝+ inch. Mature stems become hardened and tough. Larger plants have a few relatively short (to 2 ft long) branches along their upper portion. Stems are densely covered with short dense hispid pubescence which extends onto branches as dense pilose pubescence. While pubescence of stems may be reddish, that of branches is clear. Slight longitudinal ridges extend down from the leaf petioles so that the lower stem becomes 8-sided in cross-section. With drying soils, plants are subject to the loss of lower leaves. Dried leaves hang down and persist. As the bloom period ends in late September, the entire plant quickly dies, though typically remaining erect into spring.

Photo 1: First year plants have ascending petiolate elliptical leaves. As shown, soil has been removed from plant at right to expose a 6-inch taproot with a swollen segment. Photo – October 8.
Photo 2: New basal leaves of this second year plant are well armed with spines and long pubescence. Photo – February 20.

Stem leaves are alternate, green above and prominently white beneath. They become gradually smaller up-stem and toward the branch tips, with those at the base of flowerheads becoming bract-like. On mature plants, the largest leaves occur lower on the stem where they may be 1 foot long and 5 inches wide, often drooping with age. Larger leaves are sessile, the blades narrowing at the base. The upper leaf surface may be glabrate (hairless) or densely short hispid; the lower surface is white with a dense mat of minutely short appressed wooly hairs. Leaves are generally lanceolate (larger leaves) or elliptic (smaller leaves) in overall outline, varying from uncut to deeply pinnately lobed from plant-to-plant and even on the same plant. Leaves on sunny-sites tend to be lobed whereas plants in the shade tend to bear uncut leaves. Lobed leaves have about 5 alternate pairs of narrowly triangular lobes (incision does not extend to midrib) and a similar apical lobe. Lobe margins are mostly smooth (entire) with a large terminal spine and a few smaller lateral spines; margins of unlobed leaves are mostly serrate with small spines at the tips of the teeth. In general, the leaf outline is consistent for an entire plant, but upper leaves of a lobed plant may become gradually unlobed. Venation, recessed above and expressed below, is pinnate, with secondary veins of deeply lobed leaves terminating as spines at the lobe tips.

Photo 3: This plant has produced a stout stem with large lobed leaves. Leaves will droop with age. Photo – May 1.
Photo 4: Plants are leafy, but lower leaves wither with drying soil. Plant at center has varying leaf outlines. Undersurface of leaves is white. Photo – June 15.

The inflorescence, in August to September, consists of single composite flowerheads growing on peduncles from the uppermost leaf axils. Involucres of the flowerheads are ball-shaped in bud and become vase-shaped in bloom. They comprise tightly imbricated, lanceolate phyllaries (bracts), spirally arranged in about ten series. Phyllaries are medium green along their upper exposed half, typically with a central whitish stripe. They terminate in slender straight piercing spines. Spines lower on the involucre project outward or downward while upper spines tend to be ascending and may be up-hooked at their tips. There may be a dark spot at the base of the spine. Phyllaries are broader at the base of the involucre and become lanceolate to linear at the rim, with the linear phyllaries to ⅝ inch long.

Photo 5: Serrate leaf margins are spiny to a greater or lesser degree. Venation is pinnate. (These four stems developed after the original stem apex was damaged.) Photo – June 30.
Photo 6: Involucres are composed of tightly imbricated phyllaries which may have a dark spot at the base of the spine. Leaves below flowerheads may be few or clustered. Photo – August 4.

Flowerheads are composed of 100+ perfect disk florets, each with five stamens and a pistil. Florets are densely packed within the confining involucre so that marginal florets “mushroom” over the edge, broadening the flowerheads to 2 inches across. Florets, in pink to lavender shades (rarely white), have slender tubular corollas with 5 linear lobes, 1 positioned below the style and 4 above. Corolla tubes attach to the tops of the stubby-elongate inferior ovaries, each encircled by a pappus of inch-long, white bristles. As florets approach anthesis (blooming centripetally from involucral margin inward), corollas elongate beyond the pappus. The 5 stamens, with fuzzy white filaments, are tipped with elongate anthers fused into a ring. The anther ring is exserted beyond the corolla tube. As the style exserts through the anther ring, it picks up and carries the white pollen well beyond the anthers, making it available to foraging pollinators. As the anthers fade and the pollen is dispersed, the darker colored, minutely bilobed stigma at the tip of the style is fully exserted. Individual florets are about 1 inch long with a ¾ inch slender tube (hidden within the involucre) and ¼ inch lobes.

Photo 7: Arrows on flowerhead at left identify: white anther tubes with purple style tips just emerging (red arrow), white anther tube (yellow arrow) and emerged, elongated style and stigma (white arrow). Note pappus covering center of flowerhead at left and changes of phyllary size and shape of flowerhead at upper right. Photo – September 4.
Photo 8: Florets are densely packed within the involucre. The slender corolla tubes are tipped with five lobes, as can be seen at far left, along with anther ring and emerging style. Note the white pollen.
Photo 9: Single disk floret removed from receptacle. Arrows: ovary (white), corolla tube (blue), corolla lobes (pink), style (green), pubescent filaments (red), and anther ring (orange). (Style has not yet split to reveal two minute terminal lobes.)

As early flowerheads pass anthesis, the heads fade while others are still in bloom. With completion of flowering in late September, the entire plant dies. As the fruits (achenes) within an involucre mature, a mass of achenes and pappus expands. Some clumps, especially in wet weather, drop near the parent plant while some individual achenes becoming airborne. The light brown, slightly ribbed, bullet-shaped achenes (flat top and pointed base) are <¼ inch long with apical collars that allows the inch-long pappus to easily separate.

Photo 10: Bullet-shaped 1-seeded achenes are forced out of the involucre as they enlarge. Photo – October 1.

For a garden or natural area, tall thistle’s droopy lower leaves tend to die so that plants may become unattractive. However, when the showy flowerheads appear, it reasserts itself as a striking plant. Nectar is favored by butterflies and the achenes are a valuable food source for finches and other small birds and small mammals. Tall thistle is somewhat shade tolerant. Plants may self-seed too well, but young plants can be removed while in the rosette stage. It is not eaten by deer.

Photo 11: Tall thistles provide nectar to Pipevine Swallowtails (Battus philenor, shown here) and other butterflies.

Tall thistle is one of nine species (two non-native) in the Cirsium genus in Arkansas, all having pink to lavender flowerheads. Of the other eight species, the ones (all native) with the most similar leaf outline are Carolina thistle (Cirsium carolinianum), field thistle (Cirsium discolor), swamp thistle (Cirsium muticum), Englemann’s thistle (Cirsium engelmannii), and Nuttall’s thistle (Cirsium nuttallii). Tall thistle has generally less lobed leaves, or when lobed, more broadly so, than the other species. It also has leafier upper stems and peduncles. Like many large Composite genera, though, the species distinctions are not always clearly marked.

In addition to the nine Cirsium species, six additional “thistles” in the Composite family occur in Arkansas, namely, three in the genus Carduus (lavender to purple flowers on heavily spined stalks), one in Centaurea (yellow flowers), and two in Sonchus (“sow-thistles”; yellow flowers).

Article and photographs by ANPS member Sid Vogelpohl

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Know Your Natives – Toothed Spurge

Toothed spurge (Euphorbia dentata) of the Spurge (Euphorbiaceae) family is a drought-tolerant summer annual with milky sap and a complex, bizarre inflorescence called a cyathium. The genus name recognizes Euphorbus, a Greek physician.* The specific epithet is from the Latin for “toothed” in reference to the leaf margins. The common name “spurge” derives from the Latin for “purge,” from the use of Euphorbia species as a purgative. In the U.S., toothed spurge occurs primarily from northeastern Colorado to Pennsylvania, south to southern-most Texas and east to Alabama and the Carolinas, as well as in disjunct populations in Arizona and California. In Arkansas, the species occurs statewide. Habitat preference is dry to mesic sandy to clayey soils found in woodland borders and openings, prairies and disturbed habitats, such as fields and roadsides. It is also called summer poinsettia and green poinsettia (and was formerly named Poinsettia dentata).

Toothed spurge, germinating with warm temperatures, varies considerably in size and structure, as determined by both habitat and summer weather. In most habitats, stems and branches are a pale green, but they may be reddish in full sun, with plant height varying from several inches to 3 feet. Plants have a single stem with a branched tap root supported by descending fibrous roots. The terete stems are straight, stout and erect. Larger plants have lateral branches set-off the stem at about 45⁰. Plants typically do not have sub-branches of an appreciable size.

Leaves, in opposite decussate pairs lower on the stem, may be in whorls at mid stem and again opposite or alternate on the upper stem. Robust plants may bear multiple branches of varying size from enlarged nodes. Internodes vary from ½ to 3½ inches. At the time of flowering, with lower leaves dropping off early (caducous), leaves are concentrated at ends of branches where they are associated with the inflorescence (see below). Lowermost lateral stems are longest with higher lateral stems gradually decreasing in length. When damaged, stems and leaves exude white sticky acrid sap.

Photo 1: This young plant has characteristic simple toothed leaves. Lower leaves are in opposite decussate pairs. Photo – May 9.
Photo 2: Plants generally have an open structure as a result of long internodes and caducous lower leaves. As shown by inset, mid-stem nodes may be prominent and support “extra” branches. Photo – September 21.

Leaves are simple and petiolate with considerable variation in shape and size. Generally, lower stem-leaves are ovate-elliptic with a wedge-shaped (cuneate) base and acuminate to acute apex. Leaves on branches may become elliptic-lanceolate and those on plants in full sun lanceolate. A large elliptic leaf may be 4 inches long and 1¾ inches wide, including a 1-inch petiole. Leaf blades are generally medium green above and yellowish green below, although in sunny habitats leaves may be reddish above (or with a few randomly scattered purplish-red blotches) and greenish red below. Leaf margins, somewhat crinkly, vary from shallowly toothed on elliptic leaves to sub-entire on lanceolate leaves. Venation is offset-pinnate with secondary veins diffusing just before reaching the leaf margin. Veins are slightly depressed on the upper surface and prominently expressed below. All veins are lighter in color than the blade. Petioles are slightly winged below the blade, flattened above and rounded below.

Pubescence varies with habitat, but generally plants have erect filiform hairs overall, except for the inflorescence itself. Hairs of lower stems and branches may be soft or hispid, depending on habitat, while the upper stems and branches may be puberulent. Leaves are glabrous to somewhat pubescent above and densely pilose beneath. Petioles and floral bracts (see below) are pubescent beneath.

The inflorescence at the tips of most branches consists of flat-topped cymose clusters, to 1+ inches across, of tightly spaced one-sixteenth-inch-wide cyathia (described below). A well-developed cluster consists of 1-3 cymes, each comprising up to a dozen cyathia. Each cyme is set atop a straight floral stem and subtended by leaf-like lanceolate floral bracts (¼ to 2½ inches long) and larger floral leaves that are typically shaded white to reddish at the base of their upper surface.

Photo 3: This flat-topped cluster of tightly spaced cyathia consists of 3 cymes on separate floral stems with floral bracts and floral leaves. Note filiform pubescence. Photo – September 19.
Photo 4: Bracts and leaves immediately below the inflorescence have white to reddish shading at their bases, but are totally red in full-sun habitats.
Photo 5: Well-developed clusters, as shown, have 3 cymes. Each cyme is subtended by 2 floral bracts and 1 (sometimes 2) floral leaves. In display, floral leaves removed to show upper and lower surfaces. Leaves of full-sun plants (at right) tend to be lanceolate.

The cyathium is the unique, primary inflorescence of the large, worldwide genus Euphorbia. The cyathium of toothed spurge is a bowl-like, glabrous, yellowish green to reddish involucre (the modified receptacle) of five united, pinkish fringed (fimbriate) bracteoles that enclose a central pistillate flower and a number of staminate flowers. A distinct funnel-shaped nectar gland, attached to the outside of the involucre, has a shiny green apex shaped like pursed lips. Each apparent stamen is morphologically an entire staminate flower reduced to a single stamen––a microscopic joint in its stalk marks the separation of the pedicel (below) from the filament (above). Each filament bears a single two-lobed pale yellow anther. Similarly, the apparent pistil is morphologically a reduced pistillate flower. After the pistillate flower “blooms” and the stigma is no longer receptive, the anthers release light yellow pollen––a behavior that reduces the chance of self-pollination. Cyathia develop from the base of the cymes outward.

Photo 6: Involucres of cyathia comprise fringed bracteoles (red arrow). Cyathia bear a female flower (white arrow), male flowers (yellow arrow), and a nectar gland (black arrow).

The pistil of the female flower has a glabrous, globose ovary with 3 spreading styles tipped by minute stigmas. At anthesis, when the pistillate flower is “in bloom,” the ovary is hidden within the involucre. The rounded 3-lobed ovary has three chambers, each containing an ovule. The ovary is attached to a gynophore (a stalk supporting the ovary) which, if the ovary is fertilized, lengthens and exserts the developing fruit from the involucre. The ovary then becomes significantly larger, initially dangling from its down-curved gynophore. As the fruit matures, the gynophore strengthens and becomes erect, holding the seed capsule upright above the cyme.

With maturity, the fruiting capsules become light tan before they dehisce explosively to disperse up to three seeds. Seeds are brown, ovoid, tuberculate, and 1/16 inch long, with a light colored hilum surrounded by a caruncle of the same color, and a dark furrow extending from the hilum to the seed apex. After the explosive dispersal of seeds, the gynophore, topped with remnants of the capsule and placenta, remains for a short time before dropping off.

Photo 7: In these 2 cymes (a third cyme represented by “stump” at center), female flowers are seen at 3 stages of development (red arrows – bottom to top). The “posts” (black arrow) are gynophores after capsules have explosively dehisced, with remnants of the capsule and placenta remaining at their apexes.
Photo 8: Seeds, shown with capsule sections, have uniformly spread tubercles and a furrow (see furrow on right seed). (Squares = ¼ inch)

Lacking a showy inflorescence, toothed spurge will not typically be considered an attractive candidate for a native plant garden. (On the other hand, the species is quite weedy and may arrive on its own as a volunteer.) In its favor, plants are morphologically intriguing as well as offering a good food source for birds, making them welcome additions to a natural area. Excessive self-seeding, can be controlled by full-plant removal early in its growth cycle. Sap can cause contact dermatitis and is harmful to eyes.

Photo 9: In this garden setting, this recumbent plant is attractive, but was removed at this stage to prevent self-seeding. All branches terminate with an inflorescence. Photo – August 8.

Toothed spurge is one of 27 species of Euphorbia that occur in Arkansas, including 9 non-native species and 5 species of conservation concern. Only 1 of the other 26 species may be confused with toothed spurge, namely, non-native David’s Spurge (aka toothed spurge), Euphorbia davidii. Both have opposite branching, toothed leaves, and one nectar gland. However, David’s Spurge has stiff strongly tapered hairs on lower leaf surfaces and the seed tubercules are not evenly distributed. David’s Spurge has been reported from Mississippi County only.

* Euphorbus, physician of King Juba II (50 BC-AD 24) discovered a medicinal plant in the Atlas Mountains of North Africa. King Juba named the plant “Euphorbia” in his honor. The name “Euphorbia” was officially assigned to the genus by Carl Linnaeus in 1753.

Article and photographs by ANPS member Sid Vogelpohl

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Know Your Natives – Water-willow

Water-willow (Justicia americana) of the Acanthus (Acanthaceae) family is an herbaceous aquatic perennial with willow-like leaves. The genus name recognizes James Justice, an 18th-century Scottish author of horticultural books. The specific epithet denotes the plant’s area of primary occurrence. In the U.S., water-willow occurs primarily from eastern Oklahoma and Kansas in a broad sweep that extends to the Atlantic Coast, as well as extensive populations in Alabama and central Texas. In Arkansas, it occurs throughout a large portion of the state except for Crowley’s Ridge and portions of the Mississippi Alluvial Plain and the West Gulf Coastal Plain. It occurs throughout the Interior Highlands portion of the state. Habitats are sunny areas in wetlands, especially those with sandy to gravelly soils in the shallow portions of perennial streams and the muddy margins of streams, ponds and lakes.

Photo 1: Shallow areas of this rocky perennial stream, with flow from left to right, provide a favorable habitat for water-willow. Stems of colonies, all of equal height, become densely packed. Photo – August 3.

Plants have long ropy roots, short fibrous roots, and slender, occasionally branched runners (stolons). The white descending ropy roots provide nutrients and stability to the plant in its aquatic habitat. The oxygen-absorbing fibrous roots are in dense tangles at the stem’s base, below and above the soil surface, as well as at submerged leaf nodes. The creeping runners, at and just below the soil surface, produce new stems at their tips. Runners have short, linear-lanceolate, alternate bracts which may subtend a secondary runner. In a favorable site, large dense colonies develop with all stems tending to be of equal height. Plants are adapted to varying water levels up to 3 feet deep, with varying water flow rates.

Photo 2: This stem, which grew from the tip of the older brown runner at right, has long ropy roots and short fibrous roots. A new runner, growing at left, would have produced several new stems. Stem shown in this photo is from a site similar to that in Photo 1.

The light green stout stems, to 3 feet tall with a base to ⅜ inch wide, have a gradual taper to the apex, which terminates with a pair of small leaves. Stems are hexagonal with rounded corners in the lower portion, the corners becoming ribs as the stem narrows above. The erect stems are typically not branched, although separate stems may grow from a stem’s base and a few short leafy axillary branches may be present. The linear to lanceolate, glabrous leaves are medium-green above and yellowish medium-green below, from lighter green swollen nodes. They are produced in opposite pairs arranged cyclically about the stem, the largest occurring about mid-stem where they may be up to 4¾ inches long and ½ inch wide. Blade margins are slightly wavy and entire (uncut); blade surfaces may be undulating, especially along the margins. Leaves, with their gradually tapering bases, are sessile to short-petiolate (subsessile) and are up-folded along the midrib. Stems, with a white corky interior and a small hollow center, are buoyant.

Photo 3: Plants are adapted to perennial streams where flow may be nil to deep and swift. These plants are growing in a shallow-water portion of a perennial stream as compared to those in deeper water as shown in Photo 1.

The rather thick leaves have pinnate venation, with the primary (midrib) and secondary veins being expressed above and below. Venation of younger leaves is a lighter green than the blade, while veins and blades of older leaves are the same color. Secondary veins arc from the straight midrib to where they closely parallel the margin. Tertiary veins are obscure.

Photo 4: The sessile to sub-sessile willow-like leaves have upper and lower veins which are both expressed. Separated leaves show the upper surface (left) and lower surface (right).

The inflorescence, present primarily in June to July, consists of a stubby (to ¾ inch long) tight cluster of six to eight flowers at the tip of slender, erect, light green peduncles. The glabrous, ribbed peduncles, to 3+ inches long, are axillary from several uppermost leaf pairs. Elongate light green flower buds have several tiny triangular bracts appressed at their base. Lower flowers of a cluster bloom first with several closely spaced flowers often in bloom at the same time, so that multiple flowers may even appear to be a single flower. Flower buds are ascending and flowers in bloom face the sky. The loose sepals surrounding the buds are pushed open at anthesis, but return to an upright position after the flower has bloomed.

Photo 5: Long axillary peduncles bear a tight cluster of flowers. As shown by the cluster at left, lower flowers bloom first. Color contrasts of leaves, stems and nodes diminishes later in the growing season. Photo – June 5.

Flowers, although relatively small, are rather showy on close examination. The calyx is 5-lobed. The corolla is bilabiate (2-lipped) with a broad centrally-notched upper lobe and a lower lip of 3 lobes, 2 broadly elongate out-flared laterals and a distally broadening lower lobe. Corollas are about ¾ inch wide and ½ inch long. Mostly white, they have light lavender shading across the upper lobe and small to large splotches of dark lavender on both upper and lower lobes, with the splotches increasing into the throat (bee guides).

Flowers have two stamens and a single pistil (ovary, style and stigma). The white stamens, well-spaced to left and right of the style, become flattened distally, with noticeably asymmetrical anther sacs, one just below the other. Anthers open to expose dark purple oblong disks that release white pollen. The slender white style is reflexed tightly against the upper lobe and extends above the lobe to a minutely 2-lobed stigma.

Photo 6: These four flowers radiated from their rachis at the top of the peduncle so that their lavender upper lobes are positioned together. Several styles (with pointed stigmas) and stamens (with asymmetrically paired anthers) can be seen. Photo – June 5.

Ovaries of fertilized flowers develop into 2-valved, club-shaped capsules with acutely pointed apexes. The hardening capsules are rounded in cross-section with two flattened sides and two “lumps” (representing growing ovules) extending around the capsules. The flattened sides have a longitudinal seam where dry capsules split. The glabrous capsules, with persistent sepals, are initially a light green, but become a greenish brown with maturity and finally tan. The dry ½-inch long and ¼-inch wide capsules dehisce with explosive force so that the one to four round, flat seeds are forcibly ejected. Seeds, to ⅛ inch diameter, have notched bases and papillose surfaces. After seed dispersal, the dried peduncles and now-spiky cluster of empty capsules quickly drop off.

Photo 7: The hardened fruit is a pointed club-shaped capsule with green leaf-like sepals at the base. The lumps along the capsule mark two sets of developing seeds. (The two peduncles shown here are not attached to each other.) Photo – July 24.
Photo 8: The fruit cluster, peduncles and sepals dry simultaneously. When the hardened capsules dry, the valves spring back and up to four wafer-like seeds are forcibly ejected. Photo – August 4.

In its natural aquatic environment, water-willow is an important species, not just for insects, also providing shelter to snakes, amphibians and spawning fish. Water-willow may also provide some erosion control and sediment filtering. With the plant’s tendency to colonize, most home gardens would probably not have an appropriate site for water-willow, other than a container set in a sunny site, which might attract mosquitoes. Although the bloom period is fairly short, flowers are interesting and orchid-like.

In addition to water-willow, lance-leaf water-willow (J. ovata var. lanceolata) also occurs in Arkansas (southwestern two-thirds of the state). Lance-leaf water-willow, with a somewhat similar growth habit to water-willow (although often a bit shorter in stature), can be distinguished by its habitat (swamps and marshes, often shaded), inflorescence structure (loosely flowered spikes), and shorter but broader leaves. The corollas, although also having two lips, are smaller, with the lower lip divided into 3 equal-sized, down-trending and non-flared lobes. The color pattern of lance-leaf water-willow corollas is usually simpler, more uniformly white to pale lavender with a few darker lavender splotches in the throat of the lower lip.

Article and photographs by ANPS member Sid Vogelpohl

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Fall 2020 Claytonia now available for download

Read all about the ongoing activities in the Arkansas Native Plant Society by reading the Fall 2020 issue of Claytonia, the Newsletter of the Arkansas Native Plant Society.

  • Special Feature – Memories of Linda Ellis, 1951-20202 – Enjoy a look back at her life and legacy
  • Finding Ouachita Twistflower – Virginia McDaniel
  • Arkansas Natural Heritage Commission WeDigBio online event – ANPS Members Welcome to attend
  • Proposed bylaw revisions
  • And more!

    Download the issue to read more!
Posted in Know Your Natives

Know Your Natives – Hairy Woodland Sunflower

Hairy woodland sunflower (Helianthus hirsutus), of the Sunflower, Aster, or Composite (Asteraceae) family, is one of three Arkansas species with the common name “woodland sunflower.” The genus name is based on Greek words for “sun” and “flower.” The specific epithet is Latin for “hairy” or “bristly.” In the U.S., hairy woodland sunflower occurs from the Florida panhandle west to east-central Texas and north to the Carolinas, Ohio, and Minnesota. The species also occurs in south-central Canada and mountainous areas of central Mexico. In Arkansas, occurrence is statewide. Habitats include woodland edges, savannas, and prairies in loamy to rocky, moist to dry soils. Other common names are bristly sunflower and stiff-haired sunflower.

Hairy woodland sunflower bears near-surface, narrow, ropy, white rhizomes (underground stems). New plants develop at rhizome tips while the established rootstock continues to produce annual stems, so that colonies form quickly.

Photo 1: These spring-time stems are probably clonal. Dense pubescence, becoming bristly and coarse, persists throughout the growth year.
Photo 1: These spring-time stems are probably clonal. Dense pubescence, becoming bristly and coarse, persists throughout the growth year.

This herbaceous perennial produces erect to leaning, rigid stems to 5+ feet tall with opposite, decussate (alternating 90 degrees) leaf pairs. Petiole bases join around the stem as a slight ridge. Stems are densely covered with coarse, bristly hairs. Branching is limited to one to several opposite pairs of short axillary floral branches along the uppermost length of stems. A mature stem may have 10 to 20 pairs of larger leaves below the floral branches, separated by 3 to 4 inch internodes. Overwintering dead stems persist into the new year.

Photo 2: This stem has reached its mature height with the first flowerhead to bloom at the tip of the stem. Several paired axillary floral branches occur along the uppermost length of the stem. Opposite leaf pairs are decussate, emerging at 90 degree angles from one another.
Photo 2: This stem has reached its mature height with the first flowerhead to bloom at the tip of the stem. Several paired axillary floral branches occur along the uppermost length of the stem. Opposite leaf pairs are decussate, emerging at 90 degree angles from one another.

Typical leaves below the floral branches are broadly lanceolate, about 6 inches long (including petioles) and 1¾+ inches wide, with shallowly serrate margins. Like the stems, they are hirsute (coarsely hairy). Petioles, stout and pubescent, decrease in length from stem base (¾ inch) to stem apex (1/16 inch). Leaves have three primary veins: the midrib and a pair of laterals.

 

Photo 3: Display showing upper and lower leaf surfaces along with a lower and upper portion of a stem. Primary lateral veins originate off midrib at leaf blade and petiole junction. Stems and both sides of leaves are hairy.
Photo 3: Display showing upper and lower leaf surfaces along with a lower and upper portion of a stem. Primary lateral veins originate off midrib at or very near the leaf blade and petiole junction. Stems and both sides of leaves are stiff, bristly hairy.

The inflorescence, occurring for a month or more in mid- to late summer, consists of one to a half dozen or more composite flower heads per stem. Flower heads terminate the main stem as well as the stem-like peduncles (½-2 inches long) of lateral branches. 

Photo 4: Within this developing inflorescence, emerging opposite pairs of floral branches bear opposite leaf pairs as well as still smaller leaves that subtend the peduncles.
Photo 4: Within this developing inflorescence, emerging opposite pairs of floral branches bear opposite leaf pairs as well as still smaller leaves that subtend the peduncles.

Flowerheads, 2+ inches across, are set in a bowl-shaped involucre which may be from ½ to 1 inch wide. Flower heads have 10 to 16 sterile ray florets which surround up to 90 or so fertile florets in the central disk. Involucres comprise 20 or so phyllaries (bracts) in three to four imbricated series. The ¼+ inch phyllaries are lanceolate, narrowing to sharp, ascending to revolute tips.

Photo 5: The bowl-shaped involucre has several series of lanceolate phyllaries. Hirsute pubescence is dense on phyllaries, peduncles and leaves. A budded flowerhead is at lower left.
Photo 5: The bowl-shaped involucre has several series of lanceolate phyllaries. Hirsute pubescence is dense on phyllaries, peduncles and leaves. A budded flowerhead is at lower left.

Ray and disk florets are a bright yellow with the ray florets remaining at anthesis as the disk florets bloom in sequence centripetally (from the outermost disk florets into the center of the disk). Ray florets have elongate petal-like corollas (ligules) to ¾ inch long, somewhat ridged longitudinally. Disc florets are each subtended by light yellow, chaffy, receptacular bracts. The 1/4-inch-long tubular disk floret corollas have 5 stubby triangular lobes; the 5 stamens have purplish anthers, fused into a ring. At anthesis, the style emerges through the exserted ring of anthers, carrying with it their yellow pollen, which is now available to pollinators. The stamens then shrink back into the corolla, and the style divides to expose two elongate, recurved stigmatic surfaces.

Photo 6: This 2-inch-diameter flower head has 16 sterile ray florets and numerous fertile disk florets. Each disk florets is subtended by a small, chaffy bract which shields the floret prior to anthesis. Pollen presentation by the immature styles and mature (receptive), recurved stigmas can be seen.
Photo 6: This 2-inch-diameter flower head has 16 sterile ray florets and numerous fertile disk florets. Each disk florets is subtended by a small, chaffy bract which shields the floret prior to anthesis. Pollen presentation by the immature styles and mature (receptive), recurved stigmas can be seen.
Photo 7: Longitudinal section of the flower head shows the somewhat conical receptacle as well as disk florets on their inferior ovaries. Note the shrunken anther ring of the floret at far-right, as the style splits and recurves.
Photo 7: Longitudinal section of the flower head shows the somewhat conical receptacle as well as disk florets on their inferior ovaries. Note the shrunken anther ring of the floret at far-right, as the style splits and recurves.

The perfect disk florets (with stamens and pistils) have, like all composites, inferior ovaries. With fertilization, ovaries harden into dry, narrowly ovoid, 1-seeded fruits (achenes) about ⅛ inch long, with a pair of loosely attached awns at their apex. These are the familiar “sunflower seeds.”

Hairy woodland sunflower is well suited for a larger native plant garden where this tall, leaning plant with its rather aggressive colonizing nature can be accommodated. It is an important  fall and winter food source for wildlife, including butterflies, moths, birds, and small mammals. Long-dead stems can be removed for a more tidy spring garden.

Fifteen additional species and subspecies of sunflowers (Helianthus) occur in Arkansas. Of these, two other woodland sunflowers, H. strumosus and H. divaricatus may become confused with H. hirsutus. All three are widespread in the state, with similar growth habits and habitats. With close examination, H. hirsutus  may be distinguished from the other two species by morphology of the involucre and degree of pubescence (see links immediately above). Another species that may become confused with the woodland sunflowers is Jerusaleum artichoke (H. tuberosus). Hybridization among the three woodland sunflowers makes an already difficult determination even harder.

Photo 8: The “woodland sunflower” species can be distinguished by examining involucres and pubescence. Displayed left to right: H. strumosus, H. divaricatus and H. hirsutus. The “design” of three primary veins of H. divaricatus and H. hirsutus is similar (laterals join midrib at or near the leaf blade base) as compared to H. strumosus (laterals join above base). Flower head size, although not defining, can be helpful.
Photo 8: The “woodland sunflower” species can be distinguished by examining involucres and pubescence. Displayed left to right: H. strumosus, H. divaricatus and H. hirsutus. The “design” of three primary veins of H. divaricatus and H. hirsutus is similar (laterals join midrib at or near the leaf blade base) as compared to H. strumosus (laterals join above base). Flower head size, although not defining, can be helpful.

Article and photographs by ANPS member Sid Vogelpohl

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New book on Arkansas Trees, Shrubs and Woody Vines needs your help!

EDIT 9-14-2020 – We reach our goal of $1,000! Thank you to all who contributed!

The Ozark Society Foundation (OSF) is requesting support from the Arkansas Native Plant Society for the design and printing of a new publication, Trees, Shrubs, and Woody Vines of Arkansas. OSF is requesting financial support to address a portion of the graphic design expenses.

Project Description 

The book will be over 400 pages, containing photographs, illustrations and maps to identify woody flora of Arkansas. The completed book will be designed as a field guide for outdoor use and as a reference volume for schools, libraries, and individuals. 

Book production will be completed in winter 2020. At that time, OSF will promote the book, conduct public events, and provide for sales and distribution. Revenue from sales will advance the conservation work of OSF and the Ozark Society. Both are Arkansas-Incorporated, 501(c)(3) nonprofit organizations. 

Value 

The new book will be more comprehensive and relevant than any previous work on the subject. It will include descriptions of over 400 woody plants as well as up-to-date information on species names, ranges, and habitat. The book will include updated county-level distribution maps, 16 plates of botanical illustrations and more than 1,500 full-color photos. 

The book will appeal to numerous institutions with interest in an Arkansas field guide. Interest in the book will be strong in public education, ecology, and natural sciences. Conservation professionals, including botanists, foresters, and land managers, would use the book as a field or desk reference. Outdoor enthusiasts, hikers, hunters, and amateur botanists, and their membership organizations are also highly interested in the topic. 

Participants 

The book was created for OSF by co-authors University of Arkansas, Fayetteville botanist Jennifer Ogle, Arkansas Natural Heritage Commission ecologist Theo Witsell, and University of Arkansas, Fayetteville professor emeritus Johnnie Gentry. The authors coordinated with botanists, ecologists, artists, and photographers to develop the book content, including University of Arkansas at Monticello professor emeritus Eric Sundell, who reviewed the manuscript, the late Linda Ellis, who drew the botanical illustrations, and ANHC contractor Molly Robinson, who obtained photo use permissions and developed a visual key for the book. 

History 

OSF has published high-quality books on Arkansas conservation issues for more than thirty years. The work leading up to Trees, Shrubs, and Woody Vines of Arkansas started in 2012. The project initially focused on revising a previously published OSF book, a field guide to state trees, shrubs, and vines authored by Carl Hunter. Because Hunter’s original photos were unavailable and more contemporary materials were accessible, OSF chose to create a new field guide. Until recently, project progress was delayed by organizational transition, professional relocation, and the death of individuals. OSF is again actively coordinating the project with the co-authors and publishing industry businesses. In 2020, book design, printing, and distribution will be implemented. 

OSF is requesting financial support of $1,000 from the Arkansas Native Plant Society to address a portion of the graphic design expenses. ANPS support will be recognized in the book and in all promotional materials and media descriptions. 

Additional Support is being requested from: 

Arkansas Game and Fish Foundation
Arkansas Forestry Commission
Department of Arkansas Heritage
Arkansas Game and Fish Commission
Arkansas Master Naturalists 

and other groups

Click here to go directly to the donations page.

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Know Your Natives – Pawpaw

Pawpaw (Asimina triloba) of the Custard Apple (Annonaceae) family is a small deciduous understory tree with edible fruit. It is widespread in the deciduous forests of the eastern U.S., from eastern Texas and southeastern Nebraska, east across southern Michigan to the Atlantic Coast from Pennsylvania to northern Florida. In Arkansas it occurs statewide. The genus name is based on the Native American name “assimin.” The specific epithet refers to the number of petals and sepals. The common name “pawpaw” was first used by the English in the 16th century for papaya (Carica papaya) and later used by early American settlers for this species. Along with various spellings of pawpaw, other common names include Arkansas banana, wild banana, custard apple, and banango. Habitats include deep, mesic, sandy to clayey soils of rich, shaded bottomlands, floodplains, ravines, and slopes. Pawpaws have deep taproots with shallow runners that produce nearby clonal sprouts. Trees have slender and branch-free lower trunks. Mature trees are typically from 15 to 20 feet tall, but may reach 40 feet.

Leaves and branches are alternate, in two opposing rows, however this arrangement becomes less noticeable as some branches and twigs become dominant while others die away. Short reddish pubescence on new branches is lost as they age and become glabrous. New bark is yellowish green before becoming reddish brown to gray during the first year. Bark of mature trunks is thin, gray to gray-brown, with lighter splotches, corky lenticels (air pores), and minimal fissuring.

Photo 1: Trunks are fairly smooth and gray to gray-brown, with corky lenticels and minimal fissuring. Photo – March 16.

In late March into mid-April, single flowers emerge from rounded lateral buds along year-old branches. In mid-winter, the dark fuzzy flower buds are knobby. With anthesis approaching, they become yellowish green before changing to deep reddish brown to purple. First flowers tend to open before leaves appear, but then leaf growth and flower progression continues simultaneously for about a month.

Photo 2: Branch and twig growth is alternate in opposing rows. Flowers occur on twigs with the outermost buds blooming first. Dark leaf in upper corner is Ozark Witch Hazel. Photo – March 26.

Flowers, about 1½ inches across, are pendulous, with three sepals, and a veiny corolla of three larger outer petals and three smaller inner petals, both whorls a striking maroon to reddish brown. Pedicels and sepals are covered by a dense reddish brown pubescence. Flowers have a somewhat fetid scent which attracts pollinating flies.

Photo 3: When multiple flowers occur on a twig, the more distal flower(s) bloom first. Flowers change from yellowish green to reddish purple. In spring, pedicels and sepals have dense reddish brown pubescence. Photo – April 4.
Photo 4: As flowers progress from bloom to fruit, twigs continue their terminal leafy growth. Scars of previous year’s leaves each subtend a single flower (which may bear more than a single fruit). Photo – April 10.

Flowers have an elongate receptacle bearing a dense mass of numerous stamens surrounding a cluster of 3-6 separate pistils. The stamens have stubby filaments topped with tightly packed, pale yellow anthers that en mass create a brain-like surface. Pistils consist of elongate ovaries, with short styles and rounded yellowish stigmas. After anthesis, stamens disintegrate as the receptacle shrinks to eventually form a “ring-collar” at the base of the fruit.

Photo 5: Three flowers with larger outer petals and one smaller inner petal removed. The large, yellowish, brain-like structure in center of two flowers at left is the mass of tightly packed stamens, from which the stigmas protrude. Flowers maturing from left to right.
Photo 6: Flowers have three to six pistils with nearly sessile stigmas. Interior of petals is shown except the two petals on right.

Leaves emerge after flowers have begun to bloom. Short, reddish pubescence is lost with leaf maturity. Simple oblanceolate leaves grow to about 1 foot long and 3½ inches wide with ⅜-inch petioles. Margins are entire. Crushed leaves have a strong, distinctive scent, like green peppers––a useful field character.

 

Photo 7: Purplish, hairy, elongate terminal buds are naked, i.e., they lack bud scales and consist only of embryonic leaves. Rounded lateral buds produce next year’s flowers. Photo – August 5.
Photo 8: Alternate leaves in two opposing rows, are angled toward the twig tip. Principal leaves are oblanceolate. Leaves show upper (adaxial) surface except leaf on right showing lower (abaxial) surface. Photo – August 5.

Pollinated flowers may produce one or a cluster of several rounded to oblong fruits (large berries) 1-4 inches long. Fruits develop from bluish green to yellowish as they ripen and may weigh a half-pound or more. An isolated tree may produce fruit, but cross-pollination increases fruit production. The greenish pulp becomes white to yellow, soft, sweet, and delicious as the fruit matures. Fruits contain to about 10 dark brown, inch-long, smooth and shiny seeds in two rows. Peduncles, at fruit maturity, may be an inch or more long.

Photo 9: A single flower may produce one or several fruits. When ripe, fruits become less firm and detach easily from their elongated peduncles. Photo – August 14.
Photo 10: Ripened fruit quickly softens. This fruit, with a light yellowish green skin, is 3 inches long. Largest of seeds shown at right (from a different fruit) is almost an inch long. Photo – August 17.

Pawpaws, with their large leaves, striking flowers, and delicious fruits, merit a special place in gardens and natural areas. They are easy to grow in partially sunny areas as well as, once established and with adequate moisture, sunny areas. Trees in sunnier areas will be less leggy and bear more flowers and fruit. The fruits have a banana-mango (?) flavor appreciated by many people. If a colony is not desired, clonal sprouts need to be removed annually. In early winter, those sprouts can be successfully transplanted with appropriate care (shading and watering). Leaves are not eaten by deer, but fruits are a favorite of deer, box turtles, raccoons, and other small mammals. Pawpaws are host plants for the Zebra Swallowtail (Protographium marcellus), Pawpaw Sphinx Moth (Dolba hyloeus), and the Asimina Webworm Moth* (Omphalocera munroei).

Photo 11: In a sunny native plant garden, if clonal sprouts are removed annually, a leafy specimen tree can develop. This 12-year old tree produces numerous flowers and a few fruits, even without a second close tree for cross-pollination. Photo – June 27.

Dwarf pawpaw (Asimina parviflora), a species of conservation concern in Arkansas, is the only other species of the genus in Arkansas (Miller and Union Counties). Dwarf pawpaws are more shrub-like with significantly smaller but similar leaves, flowers, and fruit.

* Caterpillars of Asimina Webworm Moth bind terminal leaves into ugly wads of dead leaves. As long as the terminal buds are not damaged, branches continue normal growth the next spring.

Article and photographs by ANPS member Sid Vogelpohl

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Know Your Natives – Woodland Agrimony

Woodland agrimony (Agrimonia rostellata) of the Rosaceae (Rose) family has leafy stems terminating with a raceme(s) of small yellow flowers. The genus name is a corruption of Argemone, the botanical name of the prickly poppy. The specific epithet is based on a Latin word for “beaks,” in reference to the fruit shape. In the U.S., the species occurs from eastern Texas to eastern Kansas in a broad sweep all the way to the eastern seaboard from South Carolina to Massachusetts. In Arkansas, it occurs statewide except for some portions of the Mississippi Alluvial Plain and the West Gulf Coastal Plain. Habitat preference is for partially sunny areas with well-drained, rich to sandy soils of mixed woodlands and woodland edges and openings. Plants are also called beaked agrimony.

The plant has a small caudex with long horizontally trending fibrous roots to 5 or more inches long and several long descending ropy roots of similar length. During summer months, the caudex produces large white buds which appear as new stems in late winter.

Photo 1: The large white bud will develop into a new stem in the spring. Plants have long shallow roots as well as long descending ropy roots. Photo – July 16.

This herbaceous perennial, to 2½ feet tall, has one to several erect (sunny sites) to reclined (shady sites) sparsely pubescent stems. Alternate compound cauline (stem) leaves are distinctively odd pinnate, with one to three pairs of opposite primary (large) leaflets, a similar number of opposite secondary (much smaller) leaflets, and a primary terminal leaflet. Secondary leaflets occur as one or several pairs between the primary pairs and may also occur below the lowermost primary pair. Mid-stem primary leaves may be to 5 inches long and 4½ inches wide. All leaflets are sessile (the stalk of the terminal leaflet is the final segment of the rachis, not a petiole).

Photo 2: In early spring, this plant has several emerging stems. The odd-pinnate compound leaves are composed of primary and secondary leaflets.
Photo 3: In early summer, this 29-inch plant is in full-bloom. At this sunny site, stems and racemes are branched.

Leaves are glabrous above, while the lower leaf surface has sparse long hairs along the main veins and crowded, minute glandular pubescence between veins. Except for the smallest secondary leaflets, all leaflet margins are prominently dentate. Pairs of stipules subtending the leaves may be small and elliptical or larger––to 5/8 inch by 5/8 inch––recurving around the stem like wings. Paired leaflets and stipules are mirror images of each other. The sparse hairs that occur on stems extend onto the petioles and rachises.

Photo 4: Leaves are displayed, clockwise from far left, from stem base to stem apex. Stem segment at center is a developing apical raceme. All leaves shown with adaxial (upper) sides, except leaf at upper right corner. Note dentate margins, venation and stipules at base of petioles.
Photo 5: Long straight pubescence can be seen along the upper portion of this stem. Two recurved wing-like stipules occur where the leaf joins the stem.

The inflorescence, flowering primarily in July, comprises racemes that grow from the upper leaf axils. Total length of an inflorescence may be 1+ feet with individual racemes to 5 inches long. On a typical plant, stems transition apically into an unbranched raceme. On more robust plants, branched stems may produce several racemes which in turn may divide into secondary racemes. The erect to slightly twisty racemes bear up to 20 small, well-spaced flowers. The raceme rachis is covered with minute, stubby glandular hairs.

At anthesis, the solitary ascending flowers are about ¼ inch wide with 5 sepals, 5 petals, and 5-15 stamens attached at the rim of a densely bristly, cup-shaped hypanthium. Two pistils with superior ovaries are hidden in the hypanthium, their 2 erect light yellow styles emerging with star-shaped stigmas to the level of the anthers. The hypanthium and outer (lower) surface of the sepals are covered by minute glandular hairs. After blooming, petals and stamens quickly drop off and sepals reclose to cover the domed hypanthium.

Photo 6: Well-spaced flowers have oval petals which attach to the rim of a domed hypanthium. Flowers have 5 or more stamens and a pair of pistils (see 2 styles of flower at left).
Photo 7: Sepals, hypanthium, and rachis are covered with minute glandular pubescence. Spiky protrusions below the sepals become hooked bristles on the fruit.

The slightly nodding, ovoid fruits consist of the hypanthium with the persistent sepals reclosed across the hypanthium’s domed apex (forming the knob-like “beak”). The spiky protrusions present during flowering persist on the fruit as hardened, hooked bristles. Fruits attach to passing animals (and humans) for seed dispersal. Fruits, ⅛+ inch long and wide, contain 1-2 seeds.

Photo 8: After blooming, sepals close over the hypanthium’s domed apex so that fruits are beaked. Hooked bristles attach fruits to passing animals. Squares equal 1/4 inch.

In a shady to partially sunny garden or natural area, if this small deciduous perennial was interspersed with other leafy plants, it would hardly be noticed. However, as a specimen plant, it would present its interesting growth pattern and add an interesting leafy texture. Woodland agrimony does not seem to be an aggressive self-seeder and does not seem to be eaten by deer.

Three other species of the genus occur in Arkansas: low agrimony (A. microcarpa), southern agrimony (A. parviflora), and downy agrimony (A. pubescens). These species also have small yellow flowers in racemes and similar odd-pinnate leaves. Woodland agrimony can be distinguished by its 1) long straight cauline hairs, 2) ovate to elliptic leaflets that are mostly glabrous above and densely covered with minute glandular hairs beneath, and 3) fruits with a bowl-shaped lower half and bristles that are directed outward.

Article and photographs by ANPS member Sid Vogelpohl

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