Know Your Natives – Hispid Buttercup

Hispid Buttercup (Ranunculus hispidus var. hispidus*) of the Buttercup (Ranunculaceae) family is an upland perennial forb with mostly 3-part basal and stem leaves and has soft spreading (bristly) pubescence on stems and petioles. The genus name is from the Latin for “little frog,” because many buttercups live in moist habitats. The specific epithet is Latin for “with bristly hairs”, in reference to the plant’s pubescence. In the U.S., Hispid Buttercup can be found from Kansas, Oklahoma, Missouri and Arkansas along with a large block of states from Alabama to Wisconsin and eastward to the Atlantic Coast (far-northeastern states excluded). In Arkansas, it occurs across the Interior Highlands (Ozark Plateaus, Arkansas Valley and Ouachita Mountains). Habitats include various well-drained to compacted soils in deciduous woodlands and openings found along ridges, slopes and lowlands as well as in prairies.

Hispid Buttercup is an herbaceous plant with basal leaves at the base of flowering stems. Basal leaves, a darker green than stems, have long petioles with “winged” bases as a result of bases having clasped emerging leaves and stems. Basal leaves vary from early ovate simple leaves to 3-lobed simple rounded leaves to ternately compound leaves with oblanceolate leaflets. While terminal leaflets are symmetrical along their midrib, lateral leaflets are narrower along their distal side. The larger terminal leaflet may or may not be on a short stalk (petiolule) while the opposite lateral leaflets are typically sessile or nearly so. Bases of leaflets may be nearly flat, wedge-shaped (cuneate) or rounded. Side margins of leaves and leaflets are mostly entire while the broad apexes are rounded to coarsely dentate or sharp-pointed coarsely dentate. Leaf blades are to 6+ inches long and 5+ inches wide while petioles may be to 8+ inches long. Petioles and petiolules have long spreading pubescence. Pubescence of upper leaf blades is short, dense to scattered and somewhat appressed while that of the lower surface consists of longer spreading hairs mostly along main veins. Venation is longitudinal. Above petiole-base, petioles are grooved along their upper side and rounded below. Petiolules are terete in cross-section.

Photo 1: In this mid-summer photo, plant is growing new basal leaves which may persist over the winter months. Photo – August 1.
Photo 2: In spring, overwintering basal leaves die with growth of new basal leaves. All leaves shown are strongly 3-lobed and grooved, pubescent petioles can be seen. Photo – March 30.
Photo 3: Basal leaf in foreground is compound with a symmetrical terminal leaflet and a pair of lateral leaflets which are narrower along their distal side. The spreading pubescence of stems can be seen. Photo – April 3.
Photo 4: Venation of basal leaves is longitudinal. Leaves may be highlighted by brown margins and brown-tipped dentate serrations. (An enlarged portion of Photo 3.)
Photo 5: Terminal leaflets (here seen at bottom of photo) of larger basal leaves typically have petiolules while lateral leaflets are sessile. Detached petiole, with spreading hairs, at right. Photo – May 25.

Stem (cauline) leaves occur as widely spaced opposite pairs, near-opposite pairs and singly. Larger leaves tend to be ternately compound with narrowly elliptic to linear leaflets which typically lack lobes or marginal teeth. Distally, leaves become smaller and less complex so that the ultimate leaf may only be a simple, linear leaf. Leaflets of a compound leaf may be disjointed (not meet at a common point) and all three leaflets may have petiolules. Petioles of cauline leaves are significantly shorter than those of basal leaves with lengths decreasing distally. Primary veins are parallel. Shapes of the lowermost cauline leaves may be “transitional” by having characteristics of both basal and cauline leaves – – in regard to leaflet shape, petiole length and lobing.

Stems, few in number, are slender and radiate from the plant center. They are initially erect to ascending until they reach several inches tall. With continuing stem growth, stems become decumbent and may extend a foot from the plant’s center. Stems have one to several widely spaced, leaf-bearing nodes which may produce an axillary side stem or a flower stalk (peduncle). The pale green stems, terete in cross-section and slightly ribbed, typically have dense pubescence of spreading white hairs. Unlike some buttercups, stems in contact with the soil do not develop nodal roots.

Photo 6: Stems, not developing nodal roots, become decumbent as they lengthen. Along with several compound basal leaves, a compound cauline leaf is shown with 3 leaflets on separate petiolules. A fruit-head is shown at upper right. Photo – April 3.

Hispid Buttercup flowers from March into April. The inflorescence consists of terminal, solitary, compound flowers that arise from the uppermost cauline leaf axils. Early flower buds appear near ground level and later flowers are elevated well above basal leaves as stems continue to grow. With continued growth, flowers (and fruits) are seen as being on long slender peduncles. Peduncles (to 1+ inch long) are terete and ribbed. They are the same color as the stem, but usually less pubescent. Flowers can grow to 1 inch across.

Photo 7: Basal leaves become compound with a stalked terminal leaflet and a pair of sessile lateral leaflets. Flower buds, axillary to uppermost cauline leaves, first appear near ground-level. Photo – March 20.
Photo 8: Stems are ascending in their early growth. As shown, pubescence of peduncles is less than that of stems. Cauline leaves consist of 1-3 narrowly elliptic to linear leaflets. Photo – April 7.
Photo 9: Axillary side-stems may develop from lower cauline leaf axils. The axillary flowers are on long stem-like peduncles growing from the uppermost cauline leaf. Partially shown are Sundrops and Ernest’ Spiderwort. Photo – April 3.

The flowers consist of 5 sepals, 5 glossy yellow petals, a ring of numerous stamens (filaments + anthers) and numerous pale-yellow pistils (ovary + style + stigma) sitting on a greenish, conic receptacle. The obovate petals, to ⅝ inch long and to ⅜ inch wide, have bases and longitudinal veins that are somewhat translucent (guides to nectar at petal-base). Yellow filaments, with narrow bases, curve away from the receptacle and ascend as they transition directly into elongate yellow anthers. Anthers are smooth on their exterior and, with pollen release, grooved on their interior. The elongate pistils, evenly spread across the conic receptacle and also curved and ascending, have a skinny ovary tipped with a short style and a pin-point stigma. In bud, sepals are green and boat-shape (with a keel and sharp bow) before becoming yellowish and bowl-shaped when fully developed. The bowl-shape beginning as a flat area surrounding the peduncle. The broad sepals have a pointed apex and a narrow base. Outer surface of sepals has dense, long pubescence. Sepals, about ⅓ inch long, become somewhat reflexed and rather thin as anthesis progresses.

Photo 10: Glossy flowers have 5 petals, a ring of numerous stamens and numerous pistils on a conic receptacle. Coloration at base of petals and veins serve as guides to nectar “pockets” at base of petals (see red arrow). Photo – April 4.
Photo 11: Bowl-shaped sepals are spreading from a flat area surrounding the peduncle. Photo – April 12.
Photo 12: With anthesis, sepals become somewhat reflexed as anthesis progresses. Note obovate petals, long hairs on exterior of sepals and lack of hairs on this particular peduncle. Photo – April 12.

Receptacles have a few to 60 green fruits (achenes). When mature, the asymmetrical, flattened fruits (less than ¼ inch long) consist of a rounded seed, ⅛ inch wide, with an off-set, weakly attached base and a narrow marginal wing, about 1/32 inch wide, extending from fruit base to a sharp apical beak. The narrowly triangular, nearly straight beak (comprised of style and stigma) is firm but not piercing. Wings, too, are firm and well attached to the seed. Seed-area of the glabrous, flattened fruits are slightly thickened above the winged margins. Dry achenes may be dispersed by strong, surface water flow and passing animals.

Photo 13: Stems and peduncles are long. Cauline leaves may have 1-3 elliptic to linear leaflets. Cauline leaf at lower right is transitional between cauline and basal leaves. A basal leaf and its detached petiole are shown at upper right. Photo – May 25.
Photo 14: This cauline leaf has off-set, lanceolate lateral leaflets with parallel veins. Margins of the flattened, rounded seeds are winged with wings joined at seed apex to form a sharp beak. Fruits are asymmetrical. Squares are ¼ inch. Photo – May 27.

Hispid Buttercup, with its fresh leaves and bright yellow flowers in late winter/early spring, is noticeable. It does not seem to be an aggressive spreader and is so unobtrusive that it should be welcome in any garden setting or natural habitat. Plants grow best when in thin mulch or leaf litter. Pollen and nectar attract various bees and flies. Seeds are eaten by game birds and small mammals.

At least eighteen buttercup species or varieties have been identified in the wild in Arkansas (six are non-native). All have glossy yellow flowers except one which has white flowers (White Water Crowfoot [R. aquatillis var. diffusus]). The species most likely to be confused with Hispid Buttercup is Early Buttercup (R. fascicularis). Hispid Buttercup can be distinguished by its 1) lack of tuberous roots, 2) wider leaves and leaflets, 3) later flowers with more ovate petals, 4) spreading sepals and 4) soft, bristly pubescence.

Photo 15: Hairy Buttercup may be confused with Early Buttercup. (shown) Photo – April 2.

*A taxonomic revision placed Swamp Buttercup (R. septentrionalis) into the R. hispidus complex, which has three varieties under this concept: Bristly Buttercup (R. hispidus var. caricetorum) [not known from Arkansas], Hispid Buttercup (R. hispidus var. hispidus) and Swamp Buttercup (R. hispidus var. nitidus). Swamp Buttercup, occurring in Arkansas, has reflexed sepals, achene margins that are twice as wide as those of Hispid Buttercup and long arching-decumbent stems that may develop nodal roots. It typically occurs in riparian or lowland habitats.

Article and photographs by ANPS member Sid Vogelpohl

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