Wolffia arrhiza

Spotless watermeal

Family: Araceae · Type: perennial · Native

Spotless watermeal is a native perennial found in San Diego County in freshwater habitats at elevations below 200 meters. Flowering from spring to summer, this tiny aquatic plant produces nearly invisible green flowers. Growing less than 1.5 millimeters in diameter, it forms small spherical bodies that float just beneath the water's surface with only the center slightly emerging. Its plant body is dark green with a flat upper surface and transparent base, featuring between 15 to 100 stomates. This diminutive watermeal is unique among aquatic plants for its incredibly small size, essentially vanishing into the water ecosystem.

Habitat: Uncommon. Freshwater

Bloom period: Spring-summer

Elevation: < 200 m

Bioregions: SCo (San Diego Co.)

Data from The California Species Project — 14,000+ California species with verified data from CNPS, CDFW, USFWS, Jepson eFlora, Cal-IPC, and more.