Marsilea mutica & M. quadrifolia
Shaun Winterton, California Department of Food and Agriculture, Bugwood.org
Description: Waterclovers consist of a group of very similar and closely related plants. They are aquatic perennial ferns that are anchored in the sediment by slender, branching rhizomes that root at nodes and internodes. Leaves (fronds) arise from rhizomes on slender petioles typically 2-7" (5-18 cm) long, but up to 12" (30 cm) long if the plant is rooted deeply. Leaves may be floating or slightly emerged; emerged leaves may sometimes close at night and reopen with daylight. Each leaf resembles a 4-leaf clover with 4 wedge-shaped leaflets. Each leaflet is 0.25-1" (0.6-2.5 cm) long and wide, typically smooth above, and may have a few short hairs on the underside. Spore-producing structures (sporocarps) are attached to short, branched stalks up to 0.5" (12 mm) long arising from the bases of leaf petioles. Sporocarps are brown, hairy when young, oval-shaped, and 0.2" (5 mm) long by 0.12" (3 mm) wide. In cold climates, plants often die back to their roots in winter; they may grow year-round at warm locations.
In Oklahoma: These two species of Water Clovers are not widespread in North America, yet. The majority of observations are in the northeast with a few observations in neighboring Kansas and Missouri. Based on its current distribution in the U.S., it is unlikely to become a problem in Oklahoma’s waters. However, we should continue to look for these species and eradicate when found, but their potential for significant problems in Oklahoma is low.