Flower:

Solitary flowers at the end of branching stems in the upper part of the plant. Flowers are flattened, about 1/8-inch across, with 4 petal-like sepals that are broadly triangular to egg-shaped to semi-circular, 1 opposite pair often slightly larger than the other. Sepals are green, yellowish green or reddish green. In the center is a translucent disk, green to brown to reddish, surrounded by 4 to 8 (usually 8) short stamens, typically purple, red or orange tipped, though we have seen yellow stamens as well.

Leaves and stems:

Leaves are round to egg-shaped to fan-shaped, 3/8 to 5/8 inch long and up to ¾ inch wide, hairless, scalloped or shallowly notched or lobed around the edges, stalkless or short-stalked. Leaves are mostly opposite but may be alternate in the upper branches. Stems trail along the ground, rooting at the nodes and often create dense mats. Upper branches are prostrate to ascending.

Fruit:

Fruit is a 2-lobed capsule, oblong in outline, containing up to 16 dark brown seeds.

Notes:

When we came upon this species at Falls Creek SNA, at first glance of the marshy bend in the brook, this species appeared to be emerging Watercress (Nasturtium officinale) or perhaps Giant Chickweed (Myosoton aquaticum) but turned out to be a new find for us. We still weren't entirely sure what we had found because this particular population all had atypical yellow anthers on the flowers, not the red-orange described in texts and shown in all the imagery found on the web. A couple years later we came across it at Banning State Park with more typical coloring. The related Iowa Golden Saxifrage (Chrysosplenium iowense) does have yellow anthers, but has sparsely hairy, alternate leaves that are longer stalked and have a deep sinus at the base, where C. americanum leaves are hairless, mostly opposite, and lack the sinus and stalk. C. iowense is also quite rare, only known to be in just a few locations in the state, on talus slopes.