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.

SPIRODELA

DUCKMEAT

Plants generally in clusters of 2–5; roots 1–16, some passing through minute scale on lower surface
Plant body 3–10 mm, oblong to round, flat; upper surface dark shiny green, lower generally red-purple; veins 3–12 (visible in backlight); young plants with minute scale-like leaf on each side at base; winter buds often produced
Flowers in 2 lateral budding pouches, sheathed by minute membrane
Seed ribbed
Species in genus: 3 species: worldwide
Etymology: (Greek: visible thread, from roots)

Native

S. punctata (G. Mey.) C.H. Thomps.

Roots 1–6, all passing through minute scale
Plant body 3–5 mm, oblong-obovate, asymmetric; veins 3–5; upper surface often with row of minute bumps at midline
Ecology: Still water, coastal and interior valleys
Elevation: < 500 m.
Bioregional distribution: North Coast, Great Central Valley, Central Coast, San Francisco Bay Area, South Coast
Distribution outside California: nearly worldwide
Synonyms: S. oligorrhiza (Kurz) Hegelm