Common Water Clover

<em>Marsilea quadrifolia</em>, commonly known as the common water clover or European waterclover, is an aquatic fern in the family Marsileaceae. Its conservation status is listed as Not Evaluated by the IUCN. The species has a broad native distribution spanning Asia and Europe, and has been introduced to North America, where it now occurs in scattered freshwater habitats. It typically grows in shallow ponds, rice paddies, slow-moving streams, and muddy lake margins, rooting in soft sediments while its four-leaflet fronds float on or emerge above the water surface. The distinctive four-lobed leaves strongly resemble a four-leaf clover, lending the plant its common name. <em>Marsilea quadrifolia</em> is a heterosporous fern, producing specialized reproductive structures called sporocarps that contain both megaspores and microspores, allowing reproduction under conditions unfavorable for vegetative growth. The plant is remarkably drought-tolerant, as sporocarps can remain viable for decades. It typically spreads through both vegetative rhizome growth and spore dispersal. Biological traits including average lifespan, height, and mass remain poorly documented in standardized databases. The species plays a role in shallow aquatic ecosystems as a colonizing plant, stabilizing soft substrates and providing microhabitat for invertebrates and small vertebrates in the temperate freshwater zones it inhabits.