Know Your Natives – Downy Ragged Goldenrod

Downy Ragged Goldenrod* (Solidago petiolaris**) of the Aster, Sunflower, or Composite (Asteraceae) family has stiff lanceolate leaves on unbranched stems that are topped by an unusually large array of golden-yellow flower heads. The genus name is based on the Latin solidus, meaning “whole,” in reference to purported health benefits of some species. The specific epithet is from the Latin for “with petiole.” In the U.S., the species occurs primarily from southern Nebraska and Texas, east to the Carolinas and northern Florida. In Arkansas, it occurs statewide except for portions of the Mississippi Alluvial Plain and Crowley’s Ridge. Preferred habitats include more or less sunny, mesic to dry, sandy to rocky areas, such as open woodlands, glades, and blufftops. It is also known as Woodland Goldenrod.

This herbaceous perennial develops a central rootstock of weakly connected segments with numerous fibrous roots. Each knobby segment bears one to several stems. Buds for the next year’s stems develop at the base of the current year’s stems. Dead stems persist into the new growth-year. Erect, fleshy springtime stems tend to be pubescent and reddish, while mature stems become reddish brown to brown below as they stiffen. Stem growth above in the inflorescence tends to be bright green before also becoming reddish to brown.

Photo 1: This rootstock, composed of five weakly connected segments and numerous fibrous roots, bears a dozen living stems while retaining dead stems. Round scars (at front) are remnants of three-year-old stems. Buds for next year’s stems can be seen at far right. Photo – August 20.

Stems, with slight longitudinal ridges, grow to unequal heights, often reaching 4+ feet tall and, at base, 3/16 inch in diameter. They are unbranched unless the growing tip has been damaged. Lower portion of stems typically loses leaves by mid-growth-year, becoming smooth except for projecting petiole bases. Depending on the site, they may be erect, ascending or sprawled.

Photo 2: Springtime leaves and stems bear short pubescence, becoming glabrate as plants mature, except for leaf margins. Photo – April 8.

Plants have alternate, simple stem leaves, narrowly elliptic, spreading to ascending, and stiff, at midstem to 4 inches long and ½ inch wide, gradually decreasing to as little as ⅛ inch long in the terminal inflorescence. They are sessile to short-petiolate, with margins entire (smooth) to shallowly serrate distally, the teeth mucronate. Upper leaf surface is green with a satin sheen, the lower surface with a dull sheen. Venation is pinnate with a single strong midvein and secondary veins that curve forward to parallel the margins. Mature leaves feel slightly rough from microscopic hispid pubescence, with hairs more prominent on the main veins beneath. Margins are ciliate with the hairs angled toward the apex. As soil dries during summer, leaf-drop proceeds up-stem.

Photo 3: Stems have closely spaced narrowly elliptic, simple leaves that extend from stem base into the inflorescence. Dead stems persist into the new growth year. Photo – March 4.
Photo 4: Upper surface of a 2½ inch leaf shown above, the lower surface below. Ciliate pubescence of upper leaf can be better seen in its shadow. Secondary veins curve and parallel the margins. Tertiary veins are reticulate. Photo – August 28.
Photo 5: Set of three leaves at top, left and right are from different plants. Left leaves are serrate while top and right leaves are entire. Margins are narrowly downturned, as can be seen on lower left leaf. The lower stem segment is 3⅛ inches long and 3/16 inch wide. Pubescence is not visible on leaves or stem. Photo – August 31.

Composite flower heads, with ray and disk florets, bloom in September and October. The axillary inflorescence, along the upper portion of the stem, consists of individual flower heads and tightly branching clusters of 3 to 7 flower heads, forming columnar or spikelike panicles. An inflorescence may be 4 to 10 inches long with up to 150+ heads, the flowering proceeding from apex to base. Individual heads or clusters are subtended by a small leaflike bract. While pedicels of single flower heads are consistently short, peduncles of clusters may be a bit longer (to ½+ inch). When plants are erect, flower heads are arranged equally around the stem; when sprawled, heads twist toward sunlight so that the inflorescence is secund (heads all on upper side). Pedicels and peduncles bear closely spaced linear-oblong bracts that transition to the linear-lanceolate phyllaries of the involucre (to ¼ inch long). Heads are about ¼ inch long and ⅛+ inch wide. Pedicels, peduncles, bracts, and phyllaries are light green with short hooked pubescence, that of the phyllaries being glandular.

Photo 6: Developing inflorescence of two stems at left consists of individual flower heads. Tip of stem at right was apparently damaged, so that lateral branches developed. Stem leaves may continue into the inflorescence (right stem) or transition to bracts (left stems). Photo – August 26.
Photo 7: Flowerheads on spreading to sprawled stems twist sunward so that the inflorescence is secund, but leaves remain arrayed about the stem. Plant at lower right is Goat’s Rue. Shrubs are Sparkleberry. Photo – October 25.
Photo 8: Flowers of this inflorescence (a panicle) are in tightly branched clusters, the distal heads blooming first. Blooming sequence of inflorescences begins at the apex. Photo – September 7.

The golden yellow flower heads comprise 5-10 pistillate (with pistils only) ray florets that surround 8-18 perfect (with pistils and stamens) disk florets subtended by an elongate cuplike involucre. The involucral bracts (termed phyllaries in the composites) are disposed in 3-4 series, with spreading to sharply recurved, triangular tips that give the heads a bristly appearance. Inner and outer surface of phyllaries bear minute glandular pubescence which may cause them to feel viscid. Heads bloom centripetally, from the ray florets inward to the center. Ray florets have a single linear to oblong ligule (the exposed portion of the corolla), ¼+ inch long, that has several longitudinal pleats, a rounded apex and tapered base.

Disk florets have tubular corollas, 5 stamens (filaments + anthers) and 1 pistil (ovary + style + stigma). The corollas, about 3/16 inch long, are topped with five narrow, erect, triangular lobes. Anthers of the free staminal filaments are fused together into a ring surrounding the style. As the style elongates through the anther ring, it carries the pollen above the corolla, where it is available to be dispersed by pollinators. With pollen released, anthers wither and the exserted style narrowly bifurcates to expose linear stigmatic surfaces for pollen capture. Corollas of disk florets are surrounded by a pappus of straight hairs, attached to the summit of the inferior ovary.

Photo 9: Clusters of flower heads seen from below and above. Pedicels and peduncles bear bracts that transition to the overlapping phyllaries. Bifurcated styles of two ray flowers can be seen in lowermost flower head. A number of slightly bifurcated styles of disk florets can also be seen. Photo – October 3.
Photo 10: Flower head shows: 1) flowering sequence moving from ray florets toward center of head, 2) 5 lobes of the tubular disk florets, 3) raised margin of disk corolla lobes, 4) slender filaments and anther rings, and 5) extruded pollen (far right). Elsewhere: 1) hooked ciliate pubescence on leaf (lower left) and 2) glandular pubescence on recurved phyllaries (upper left). Photo – October 18.

Fertilized ray and disk florets produce flattened elongate achenes (referred to as cypselae in Aster family) topped by pappus. The ⅛ inch long achenes are longitudinally ribbed. Dry pappus radiates from the apex of the achene where it provides lift for wind dispersal.

Photo 11: As flower heads dry, the enlarging ovaries/cypselae bulge upward as the exposed pappus dries and radiates from summit of the elongate cypselae. Photo – November 11.

Downy Ragged Goldenrod, with its large and decorative, late-summer and fall inflorescence, is an excellent choice for a wildflower garden. As with other goldenrods, its flowers provide nectar and pollen for a wide variety of insects, and seeds are consumed by small song birds. The long graceful stems can be somewhat “disorganized” so that staking may be needed. Plants do not spread by rhizomes. When soil dries, this species seems to be more prone to leaf drop.

Downy Ragged Goldenrod is one of some 30 or more species, subspecies, and varieties in the Solidago genus recognized in Arkansas. Of all these species, it most closely resembles Buckley’s Goldenrod (Solidago buckleyi) which has a similar inflorescence and spreading to recurved phyllaries. Buckley’s Goldenrod has fewer and significantly larger and thinner leaves that consistently have prominent marginal teeth.

*“Downy” may be a reference to early pubescence of stems and leaves which is mostly lost with plant maturity. “Ragged” may be based on the plant’s overall appearance at bloom-time: its long unbranched stems of varying lengths; its firmly positioned, often sprawling and twisty stems; and leaves that drop as available moisture declines.

** Leaf and phyllary shape and pubescence are variable across its range. Some authorities recognize varieties that are not addressed here. Arkansas plants are in need of further study.

Article and photographs by ANPS member Sid Vogelpohl

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