Potentilla pensylvanica (Prairie Cinquefoil) - photos and description



Bractlets as long as sepals

Bractlets as long as sepals.

Stem leaf top surface in above photo.

Stem leaf bottom surface in above photo.

Basal leaf top surface in above photo.

Basal leaf bottom surface in above photo.

General: Perennial with a branching caudex, stems one to several, erect to decumbent, branching above. Stems tomentose with long, spreading hairs.

Flowers: Flowers in congested cymes at stem ends. Flowers are bright yellow, measured to 10 mm diameter. Petals slightly longer than sepals, petals measured to 6 mm long, sepals measured to 5 mm long. Sepals ovate, bractlets lanceolate. Bractlets about equal in length to sepals, both 5 mm long.

Leaves: Basal leaves pinnate with up to 9 leaflets, the leaflets pectinately divided over half-way to midrib (pectinately = pinnatifid with narrow, closely set segments; comb-like). The stem leaf highlighted in the photo above was measured at 62 cm long by 33 mm wide. Stem leaves alternate, reduced in size upwards. The stem leaf highlighted in the photo above was measured at 40 mm long by 20 mm wide. Leaves green to greyish-green above, and greyish-green to greyish-white below.

Height: Height listed in Budd's Flora to 40 cm. We measured plants to 41 cm tall.

Habitat: Dry prairie and open slopes.

Abundance: Common.

Origin: Native.

Similar species: This plant is very similar to P. bipinnatifida. Reading through various prairie floras, the difference between the two species is trivial; the only reliable difference I could find between the two is the ratio of the length of the bractlets of the epicalyx to the sepals. From Flora of Alberta: "P. bipinnatifida has "bractlets of epicalyx oblong-lanceolate, shorter and narrower than sepals", while P. pensylvanica has "bractlets about as long as sepals or slightly longer".

Budd's Flora
distinguishes based on the colour of the undersides of the leaflets, which is so open to interpretation I find it useless - P. bipinnatifida has "leaflets white tomentose below", while P. pensylvanica has leaflets "grayish pilose to hirsute below".

When and where photographed: We took the above photos on July 13th, prairie, Cypress Hills, about 425 km southwest of our home in Regina, SK.