Potentilla supina L.
CC = 8
CW = -3
MOC = 16
SRank = S2
Family - Rosaceae
Habit - Annual or biennial, rarely short-lived perennial forb.
Stem - Spreading to ascending, to 50 cm, sometimes multiple from the base, branched, moderately to densely pubescent with relatively long, fine, spreading hairs, occasionally glabrous toward the base.
Leaves - Alternate, compound, petiolate, stipulate. Petioles 1-6 cm long, hairy. Stipules 5-15 mm long, leaflike, broadly lanceolate to broadly ovate, bluntly pointed at the tip, the margins entire or occasionally toothed and often hairy, the surfaces hairy, especially along the veins. Leaf blades 3-15 cm long, odd-pinnately compound with usually 5 or 7 leaflets, these 1-3 cm long, oblanceolate to elliptic or obovate, rounded to bluntly pointed at the tips, the margins coarsely toothed or scalloped, the upper surface green, sparsely to moderately hairy, the undersurface lighter green, moderately hairy.
Inflorescence - Terminal panicles or racemes, mostly with numerous flowers, particularly later in the season.
Flower - Bractlets 5, 2-5 mm long, narrowly elliptic, sparsely hairy, more densely so along the margins. Hypanthia 3-4 mm in diameter, saucer-shaped to shallowly cup-shaped. Sepals 5, 3-6 mm long, broadly ovate, sharply pointed at the tips. Petals 5, 2.5-4.0 mm long, obovate, yellow. Stamens 20. Ovaries with the styles attached near the tips.
Fruit - 0.7-1.3 mm long, smooth or somewhat wrinkled, brown, with a corky, winglike appendage along the inner margin.
Flowering - May - September.
Habitat - Streambanks, lake margins, railroads, roadsides.
Origin - Native to the U.S.
Lookalikes - Other species of Potentilla.
Other info. - This is one of the less common Missouri cinquefoils, thus far found exclusively in counties bordering the Missouri and Mississippi Rivers. It is easily differentiated from the other Missouri species of Potentilla by its pinnately compound leaves bearing five or more leaflets. The plant tends to flower quite profusely later in the season.
Photographs taken at Klondike County Park boat ramp, St. Charles, MO, 5-15-2014, and at Riverfront Park, Washington, Franklin County, MO, 6-1-2018 (SRTurner).