Flower:

Solitary flowers from the upper axil and the tip of a stout, usually naked stem rising an inch or 3 out of the water, maybe 2 or 3 buds but only one flower opening at a time. Flowers are ¼ to just over 1/3 inch across with usually 5 (sometimes 4, but up to 14) shiny, egg shaped, yellow petals, numerous orange to yellow stamens around a green center, and 4 or 5 spreading yellowish green sepals that are as long as or shorter than the petals.

Leaves and stems:

Most of the plant is submerged, except when stranded in mud. Leaves are simple (but often appear palmately compound) and alternate, hairless, semi-circular to kidney shaped in outline, typically wider than long, mostly ¼ to 1 inch wide, deeply dissected into 3 primary lobes that are further lobed/dissected several times by 2s and 3s into many narrow segments with rounded tips.

Submersed leaves are typically larger, up to 3½ inches wide, more finely divided, the segments linear, sometimes thread-like. Emersed or floating leaves are smaller, less divided and strongly pentagonal in outline. Stems are smooth to sparsely and minutely hairy, hollow and weak, sprawling on land, floating and spreading in water, rooting at the nodes, the flowering tips strongly erect.

Fruit:

The flower center expands to a round to oval seed head up to 1/3 inch long, the seeds smooth with a narrow or thread-like beak.

Notes:

While Small Yellow Water Crowfoot is very similar to Large Yellow Water Crowfoot (Ranunculus flabellaris), as its name implies it is indeed smaller in both flower and leaf size (roughly half). Compared to R. flabellaris the leaves of R. gmelinii are also typically wider than long and submersed leaves tend to be less finely divided than R. flabellaris. Other than size differences it should also be noted that stems of R. gmelinii can be minutely hairy, especially on the new growth, where R. flabellaris is smooth throughout. R. gmelinii is also the more northern of the two species, with northern portions of Minnesota, Wisconsin, Michigan along with North Dakota and Maine bordering the extreme southern edge of its North American range outside of higher elevations in the Rocky Mountain states. In this regard it is also smaller in both range and frequency in the Upper Midwest. While not considered rare in Minnesota, it is not especially common and is listed as Endangered in Wisconsin. With its preference for cooler habitats, R. gmelinii is going to be found in creeks, streams and ponds associated with cool forested swamps, marshes or groundwater seepages.