1. Ranunculus abortivus L. (small-flowered crowfoot, early wood buttercup)

R. abortivus var. indivisus Fernald

Pl. 519 h–j; Map 2367

Plants biennials or short-lived perennials. Roots not tuberous (but sometimes enlarged basally). Stems 10–70 cm long, erect or strongly ascending, not rooting at the lower nodes, glabrous, without bulbils, the base not bulbous-thickened. Basal leaves present at flowering, moderately to long-petiolate, the blade 1–4 cm long, 2–5 cm wide, kidney-shaped to more or less circular, simple, unlobed or sometimes the innermost 3-lobed, the base shallowly to deeply cordate, the margins otherwise finely to coarsely scalloped. Stem leaves sessile to short-petiolate, the blade deeply 3- or 5-lobed or -compound, the segments narrowly lanceolate to obovate, the broader ones toothed or narrowly lobed along the margins. Sepals 5, 2.0–2.5 mm long, spreading or reflexed from the base with age (lacking a transverse fold or joint), plane. Petals 5, 1.5–3.5 mm long, 1–2 mm wide, elliptic, slightly shorter than the sepals, yellow (sometimes fading to tan or white). Style present but minute. Head of achenes 3–6 mm long at maturity, ovoid-globose, the receptacle sparsely hairy. Achenes 1.4–1.6 mm long, turgid, the dorsal margin broadly and bluntly angled, the wall thick, smooth, glabrous, the beak 0.1–0.2 mm long, slender, curved. 2n=16. March–June.

Scattered to common nearly throughout the state (nearly throughout the U.S. [including Alaska], but excluding some western states; Canada). Banks of streams and rivers, margins of ponds, lakes, and sinkhole ponds, bottomland forests, mesic to dry upland forests, bottomland prairies, loess hill prairies, and ledges of bluffs; also pastures, fallow fields, old fields, orchards, lawns, ditches, roadsides, and open, disturbed areas.

Ranunculus abortivus and R. micranthus are superficially very similar in appearance, but the latter species can be distinguished by its hairy lower stems and petioles, tuberous-thickened roots, glabrous receptacles, and fruits with slightly longer beaks. It also tends to occupy the drier portion of the range of habitats in which R. abortivus can be found. Attempts to divide R. abortivus into varieties are unwarranted (Whittemore, 1997).