Landoltia punctata

History of Spread

Landoltia punctata (Dotted Duckweed) is probably a native of southeast Asia and Australia, where isozyme studies indicate that this plant has its highest genetic diversity. Some botanists consider it to be a native to North America, but no North American specimens are known prior to 1930, when it was collected in Kansas City MO. This tiny floating plant appears to have spread rapidly across the southeast US, and first appeared on the West Coast in the San Francisco Bay area in the 1950s. It has also been found in Clatsop County OR and southern CA. On the East Coast, several isolated occurrences are known from PA and Eastern MA. The likeliest vectors for its introduction to North America and the Chesapeake Bay region are the aquarium and water-garden trades (Landolt 1986; Florida Caribbean Science Center 2001).

In the Chesapeake Bay region, Landoltia punctata was first collected from ponds at Kenilworth Aquatic Gardens, Washington DC in 1951. The herbarium specimen was noted as the second North American record (U.S. National Herbarium collections). It was reported from 'still water' of the Chickahominy River in Charles City County, where the river is tidal (Wass 1972). It is now known from 9 counties bordering tidal tributaries on the Western Shore of VA (Harvill et al. 1992), including King George County, where it is reported from 'ponds and fresh marshes' (Simmons et al. 1995). It is also frequent in the Washington DC area (Landolt 1986), Woodrest Creek (U.S. National Herbarium collections), on the Aberdeen Proving Grounds (MD) along the upper Bay, and Lums Pond DE, which discharges into the Chesapeake and Delaware Canal (Florida Caribbean Science Center 2001).

Florida Caribbean Science Center 2000; Harvill et al. 1992; Landolt 1986; Simmons et al. 1995; U.S. National Herbarium collections; Wass 1972

Invasion Comments