Flower:

Open clusters of 1 to 3 flowers on 1-inch stalks at the tips of branching stems. Flowers are ¾ to 1 inch across, deep reddish purple with 5 to 8 lance oval petals alternating between narrowly triangular (or swollen in the middle) sepals twice or more as long as the petals. Sepals are also maroon, densely hairy on the upper half and sharply pointed at the tip. The flower center is dark purple, surrounded by many purple stamens with yellow pollen edging the tips (anthers).

Leaves and stems:

Leaves are alternate, pinnately compound with 5 to 7 oblong to elliptic leaflets. Leaflets are 1 to 3 inches long, rounded tip at the tip, rounded to slightly tapered at the base, sharply toothed around the edges, the upper surface smooth, the underside waxy, stalks variously hairy. Lower leaves are long stalked (but all leaflets are stalkless), the lower half of the stalk with long, wing-like leafy appendages (stipules) that sheathe the stem.

Leaf stalks shorten and stipules broaden as leaves ascend the stem, becoming short stalked with 3 leaflets in the flower clusters and the stipules nearly free. Stems sprawl, submerged and ascending in water, coarsely branched, the lower stem somewhat woody, smooth and reddish brown, but green with fine spreading hairs just below and in the flower clusters.

Notes:

Marsh Cinquefoil, formerly known as Potentilla palustris, deviates from most other Potentillas not only in its deep maroon colored flowers but also in having more than just five petals, typically 6-8. And while many of the yellow flowered species require moist habitats, this species appears to require persistently watery habitats and is completely at home in free standing water, its stems submerged with aquatic roots and just the upper stems ascending above the water line. While its northern latitude range implies a preference for cooler temperatures, it's not overly fussy and is common along marshy road ditches and drainage channels throughout much of Minnesota, especially the northern part of the state.