Water pennywort is a relatively small perennial plant that seldom exceeds 10 inches in height. Leaf petioles arise from creeping stems and attach to the center of the leaf. Leaves are round with bluntly rounded toothed margins, up to 2 1/2 inches in diameter. Flowers are borne on separate stalks as tall or taller than the leaves. Flowers are white to greenish-white somewhat inconspicuous with tiny simple flowers that arise from a single point on the stalk Pennywort can spread across moist soil or form floating mats on the water’s surface. These mats can break off and form floating islands.
Submerged portions of all aquatic plants provide habitats for many micro and macro invertebrates. These invertebrates in turn are used as food by fish and other wildlife species (e.g. amphibians, reptiles, ducks, etc.). After aquatic plants die, their decomposition by bacteria and fungi provides food (called "detritus") for many aquatic invertebrates. The seeds of pennywort are used occasionally as food by waterfowl.

Herbicide Management Options:

Habitat: contains the active ingredient, imazapyr, which inhibits the plant enzyme AHAS (acetohydroxyaced synthase). Habitat is a systemic herbicide that is effective on post-emergent floating and emergent aquatic vegetation. Imazapyr is effective at low-volume rates and does not contain heavy metals, organochlorides or phosphates, making it safe to humans and livestock. Habitat requires the use of a spray adjuvant when applying on post-emergent vegetation.
 

Reward: is a liquid diquat formulation that has been effective on water pennywort. It is a contact herbicide. Contact herbicides act quickly and kill all plants cells that they contact. A non-ionic aquatically registered surfactant (see the label) will have to be added to the Reward solution for good results.

Clipper: 
 

Biological Management Options:There is no known biological control for water pennywort.