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.
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.
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.
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.
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.
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.
*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