LEMNACEAE

DUCKWEED FAMILY

Wayne P. Armstrong

Perennial, floating aquatics, small, clonal, in dense populations; new plants produced in budding pouch at base or along margins; may overwinter on bottom as dense, rootless, starch-filled daughter plant (winter bud); roots 0–many
Plant body 0.4–10 mm, flat and tongue-shaped to spheric
Flower 1, rarely seen, minute, appearing like 2–3 unisexual flowers, often sheathed by minute membrane; perianth 0; stamens 1–2; pistil 1, simple, maturing before stamens
Fruit achene-like, sometimes winged
Seeds 1–3, smooth or ribbed. Spp. best separated by chemistry and fruit; clones vary; magnification, backlighting generally needed to identify vegetative plants
Genera in family: 4 genera, 34 species: worldwide; ornamental in pools, aquaria
Reference: [Landolt 1986 Veröff Geobot Inst ETH Stiftung Rübel Zürich 71]
Horticultural information: TRY.

LEMNA

DUCKWEED

Plants generally in clusters of 2–many; root generally 1, generally 2–6 mm, sheath near base generally not winged
Plant body generally 2–5 mm, flat, generally widely elliptic to oblong, pale to dark green, often ± red; veins 1–5 (visible in backlight); winter buds generally 0
Flowers in 2 lateral pouches, sheathed by minute membrane
Fruit generally unwinged
Seed ribbed, generally smooth between ribs
Species in genus: 13 species: worldwide
Etymology: (Greek: lake or swamp)

Native

L. minuta Kunth

Plant bodies generally in pairs (especially when crowded, in full sunlight), 1–2.5 mm, widely elliptic to oblong, pale green; base and tip generally symmetric; margin clearly thinner than center; vein 1, obscure, < 2/3 distance from root node to tip of plant body (generally < region of visible air spaces between cells)
Seed cross-lined between ribs
Ecology: Common. Freshwater
Elevation: < 2200 m.
Bioregional distribution: California (except Modoc Plateau)
Distribution outside California: w US, S.America, Europe, n Asia
Flowering time: Aug
Transparent green plants, 2–4 mm, in 4's, are much like L. valdiviana
Synonyms: L. minima Hegelm., L. minuscula Herter
Needs study.