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Wolffia columbiana Karst.

Photo: Wolffia columbiana with Duckweeds Spirodela polyrhiza and Lemna minor (W. columbinana with Spirodela polyrhiza and Lemna minor)

Columbia Water-meal

Habitat: Ponds and still waters. [Open water (non-forested, wetland)]

Range: Southern Maine to southern Ontario and Minnesota, south to South America.

Aids to Identification: This tiny aquatic plant is the smallest of all flowering plants. It is found floating low in the water with a small portion in contact with the air. It is ellipsoid or spherical in shape, 0.8 - 1.4 mm in length, with no veins or roots. Often there is more than one layer of plants causing some to be wholly submersed. It is similar in appearance to Wolffia brasiliensis, but W. brasiliensis is punctate (dotted) with brown pigment-cells.

Photo: Wolffia columbiana and duckweeds

Ecological characteristics: Columbia water-meal often grows in association with Lemna species (duckweed).

Phenology: Reproduces by vegetative budding. Flowers are rarely produced.

Family: Araceae

Synonyms: Former names include Bruniera columbiana (Karst.) Nieuwl.

Photo: Wolffia columbiana on left, Wolffia brasiliensis on right (W. columbinana left, W. brasiliensis right)

Known Distribution in Maine: This rare plant has been documented from a total of 5 town(s) in the following county(ies): Cumberland, Kennebec, Knox, York.

Dates of documented observations are: 1979, 1981, 1992, 1993, 2002 (2)

Reason(s) for rarity: At northern limit of range.

Conservation considerations: Possibly under-reported in southern Maine.

Photo: Wolffia columbiana with duckweeds (W. columbinana amongst duckweeds