Araceae

Arum Family

Duckweeds

FAMILY: Arum family (Araceae) – Lemna genus. This genus was formerly placed in the duckweed family (Lemnaceae).

SPECIES: #1 swollen duckweed (Lemna gibba L.). #2 common or lesser duckweed (Lemna minor L.).

TO UTILIZE AS FOOD: The tiny, coin-like leaves (thalli) of species listed above are edible fresh or cooked, but cooking is recommended to kill any waterborne parasites. Other species are not reported to be edible. Duckweeds are basically floating leaves drifting freely on the waves of gentle waters. Colonies can rapidly form green carpets covering entire lakes. Roots extend a short distance into the water, but they don’t extend into the soil. Swollen duckweed (L. gibba) has a flavor like lettuce, and a texture like fresh alfalfa sprouts. Flavor quality depends on water quality. Assuming the gathering site is clean, swollen duckweed tastes equivalent to the mildest iceberg lettuce. No acrid, bitter, soapy, slimy, or resinous overtones compromise the flavor. Swollen duckweed makes a fine potherb. The initial broth is true green, delicious, and perfect for soups. No change of cooking water is necessary. Lesser duckweed (L. minor), which prefers cooler climates, is considerably less appealing and marked with an acrid bite. Gathering duckweeds is easy, but they’re mostly water, so the caloric value is low. Despite the water content, drying them is surprisingly easy. The gathering season ranges from spring to autumn. Overall, duckweeds are a fine resource, but they’re not very common in the Southwest due to the lack of aquatic habitats.

NOTES: Duckweeds are interesting plants. They’re about the size of lentils and they grow in colonies that can quickly carpet entire lakes or slow-moving streams. The first species I discovered was lesser duckweed (L. minor) along Bear Creek (near Paragonah) in southwestern Utah. I didn’t know it was edible at the time, but I documented it anyway. Over the years, I documented numerous plants of questionable edibility (anything without a verifiable reference is clearly marked as inedible). Lesser duckweed wasn’t very impressive. Stephen Facciola (p. 140) described it as somewhat harsh due to oxalates, and that seems to be an accurate description. Swollen duckweed (L. gibba) was much better. According to the Flora of North America Editorial Committee, swollen duckweed was cultivated as a vegetable in Israel. They also mention that members of the lemna family (Lemnaceae), which is now part of the arum family (Araceae), are very high in protein, up to 45% of the dry weight. Another closely related edible plant worth mentioning is Asian watermeal (Wolffia globosa (Roxb.) Hartog & Plas). It’s found in warm climates throughout much of the world, including the San Joaquin Valley of central California. Asian watermeal is the smallest flowering plant on Earth. A full-grown individual is less than 1 millimeter in length, width, and height! Due to its extraordinary rate of reproduction, high nutritional value, and mild flavor, it’s cultivated in Asian countries and sold in local markets, where it’s known as “eggs of the water.” Good things sometimes come in small packages, so don’t overlook any of these resources floating freely on gentle waters.

IDENTIFICATION: The Lemna genus is represented by about 10-15 species worldwide, of which 9 are found in the United States. Similar-looking plants of the Wolffia and Wolffiella genera don’t have roots, while those of Spirodela have numerous (4-16) roots. L. minor differs from L. gibba primarily by having flat rather than swollen thalli. Thalli are “plant bodies” where the roots, stems, and/or leaves cannot be clearly differentiated.

Description of swollen duckweed (Lemna gibba): FORM aquatic plants appearing as tiny, swollen, floating leaves with short, unanchored, sting-like roots; ROOTS usually 1 per thallus; sheaths at the bases of the roots wingless; THALLI (also called leaves, fronds, or plant bodies) occurring individually or joined in clusters of 2-5; each thallus rounded, about 2-6 mm in diameter, and with 3-5 veins; lower surfaces swollen (gibbous) due to prominent cellular air chambers and often with reddish-purple spots; upper surfaces often spotted yellowish-green; margins entire; FLOWERS minute, rudimentary, and consisting of 1 pistil and 2 stamens that are considered to be 3 unisexual flowers; sepals and petals absent; FRUITS utricles up to 1 mm long, wings well developed; seeds 1-7; HABITAT marshes, ponds, edges of lakes, or slow-moving streams; California, Arizona, and nearly worldwide in warm climates; blooming June to September.

REFERENCES: #1 swollen duckweed (Lemna gibba): leaves Small (2014 p. 99) and the Flora of North America Editorial Committee (volume 22 p. 143). #2 common or lesser duckweed (Lemna minor): leaves Facciola (p. 140).