2. Ranunculus acris L. (tall buttercup)
Pl. 518 d; Map
2368
Plants
perennials. Roots not tuberous. Stems 40–90 cm long, erect or strongly
ascending, not rooting at the lower nodes, glabrous or pubescent with spreading
and/or appressed hairs, without bulbils, the base not bulbous-thickened. Basal
leaves present at flowering, long-petiolate, the blade 1.8–6.0 cm long, 2.7–9.0
cm wide, pentagonal in outline, simple, but deeply 3- or 5-lobed or -parted,
the base V-shaped, the margins otherwise irregularly lobed and/or toothed. Stem
leaves grading from moderately petiolate toward the base to sessile near the
tip, progressively reduced toward the stem tip, the lower leaves with the blade
similar to those of the basal ones, the primary divisions wedge-shaped or
rhombic, those of the upper leaves deeply 3(5)-lobed with slender, entire or
few-toothed segments. Sepals 5, 4–7 mm long, spreading, plane. Petals 5, 8–11
mm long, 7–13 mm wide, broadly obovate, noticeably longer than the sepals,
yellow. Style present. Head of achenes 5–7 mm long at maturity, more or less
globose, the receptacle glabrous. Achenes 2–3 mm long, the dorsal margin keeled
and usually narrowly winged, the wall thick, smooth, glabrous, the beak 0.3–0.7
mm long, flattened-triangular, tapered to a slender or threadlike tip, this
0.1–0.2 mm long, straight or curved. 2n=14. May–August.
Introduced,
uncommon, sporadic (native of Europe, Asia, introduced nearly throughout
temperate North America). Pastures, railroads, and open, disturbed areas.
Steyermark
(1963) noted that this is a problem pasture weed in the northern United States
and can poison livestock. Also, milk from cattle that have ingested plants
becomes tainted with a bitter flavor.