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. aequinoctialis Welw.

Root-sheath winged
Plant bodies in pairs, 2–3.5 mm, obovate-elliptic, light green; base asymmetric; tip symmetric; upper surface tip and root node with minute bumps; lower surface light green, smooth
Seed cross-lined between ribs
Ecology: Freshwater in hot regions
Elevation: < 200 m.
Bioregional distribution: Great Central Valley, Central Coast, South Coast, Sonoran Desert
Distribution outside California: worldwide
Flowering time: Fall, Dec
Synonyms: L. paucicostata Hegelm.; L. perpusilla Torr. misapplied