Ranunculus micranthus Nutt.

Rock Buttercup

Ranunculus micranthus plant

Family - Ranunculaceae

Stems - Typically around 40cm tall, erect, herbaceous, with thick roots, villous(at least below), branching above to simple, single or multiple stems from base.

Ranunculus micranthus stem

Leaves - Basal leaves petiolate. Petiole to +8cm long, villous. Blade typically with truncate or subcordate base, suborbicular to broadly ovate or reniform, mostly glabrous but with a few villous hairs below, to +3cm broad, +2.5cm long. Cauline leaves becoming sessile above, 3 to 5-lobed, sparse villous above and below. Lobes often divided again, ultimate divisions entire or crenate.

Ranunculus micranthus leavesCauline leaves.

Inflorescence - Terminal single flowers on long peduncles. Peduncles sparsely to densely villous, to 5-6cm long but typically less.

Flowers - Petals 5, yellow to pale yellow or with some white, lanceolate, spreading, to 4mm long, 1.5cm broad, glabrous. Stamens many (+20), borne below the pistils. Filaments minute, -2mm long. Anthers yellow. Pistils grouped into a globose head to 5mm long, 3.5mm in diameter. Sepals 5, reflexed to spreading, cupped, sparsely villous on exterior, ovate to elliptic, 3mm long, 2mm broad. Achenes subrotund, surface pitted, to +/-1.5mm in diameter, with beak to .3mm long.

Ranunculus micranthus calyxYoung calyx.

Ranunculus micranthus calyxMature calyx.

Ranunculus micranthus flower

Ranunculus micranthus flowerMature flower with fruits.

Flowering - March - May.

Habitat - Slopes, ravines, bottoms, open rocky woods, disturbed sites.

Origin - Native to U.S.

Other info. - This plant is very similar to another species, R. abortivus L., but the latter has glabrous stems, typically strictly reniform basal leaves, and less divided cauline leaves.
R. micranthus can be found in moist soils of the habitats listed above. This little plant is fairly common in most of the state but seems to be more frequent in the lower half. This is one of the first plants to bloom in the spring.

Photographs taken off Northwood Rd., Platte County, MO., 4-20-00.