5. Ranunculus bulbosus L. (bulbous buttercup)

Pl. 518 e, f; Map 2371

Plants perennials. Roots not tuberous. Stems 10–50(–70) cm long, erect or ascending, not rooting at the lower nodes, moderately pubescent with more or less spreading to appressed hairs, without bulbils, the base noticeably bulbous-thickened, sometimes appearing cormlike. Basal leaves present at flowering, long-petiolate, the blade 2.0–5.3 cm long, 2.5–4.5 cm wide, ovate to more or less heart-shaped in outline, usually compound (rarely only deeply divided), with 3 primary leaflets (or lobes), the base cordate, the terminal leaflet usually stalked, the primary leaflets (or lobes) deeply lobed, the segments oblong to obovate, the margins otherwise coarsely toothed, the teeth mostly rounded to bluntly pointed at their tips. Stem leaves mostly short-petiolate to sessile, progressively reduced toward the stem tip, the blade progressively deeply 3-parted into narrower, less divided and toothed, more sharply pointed segments. Sepals 5, 5–7 mm long, abruptly reflexed along a well-defined transverse fold 2–3 mm above the base, more or less plane. Petals 5, 9–13 mm long, 8–11 mm wide, broadly obovate, longer than the sepals, yellow. Style present. Head of achenes 6–9 mm long at maturity, globose to more or less ovoid, the receptacle hairy. Achenes 2.2–3.2 mm long, the dorsal margin keeled and sometimes narrowly winged, the wall thick, smooth, glabrous, the beak 0.3–0.8 mm long, flattened, lanceolate to broadly triangular, usually tapered to a slender, minute, hooked tip. 2n=16. April–June.

Introduced, uncommon, sporadic (native of Europe, Asia, introduced widely in the U.S. [most abundantly in eastern states], Canada, South America, Pacific Islands, Australia). Pastures, fallow fields, orchards, lawns, gardens, and roadsides.

Plants of R. bulbosus are superficially similar to those of R. sardous, and can be separated most reliably by their smooth (vs. pebbled) achenes (Keener and Hoot, 1987). Steyermark (1963) noted a specimen that he collected from near Campbell (Dunklin County) in 1939 that was somewhat intermediate between the two species vegetatively, but that he determined as R. bulbosus based on its achenes.