URTICACEAE

NETTLE FAMILY

Dennis W. Woodland

Annual to (soft-wooded) trees, glabrous or stinging-hairy, monoecious or dioecious
Leaves alternate or opposite, generally stipuled, petioled, often with embedded crystals
Inflorescence various, axillary
Flowers generally unisexual, small, greenish; sepals generally 4–5, free to fused; petals 0
Staminate flower: stamens generally 4–5, opposite sepals, in bud incurved, then springing out
Pistillate flower: ovary 1, superior, chamber 1, style 0–1, stigma 1, generally hair-tufted
Fruit: generally achene (drupe)
Genera in family: 50 genera, 700 species: worldwide; some cultivated (Boehmeria ; Pilea , clearweed)
Reference: [Miller 1971 J Arnold Arb 52:40–68]
Wind-pollinated.

URTICA

STINGING NETTLE

Annual to shrub, weak, stinging-hairy or not, monoecious or dioecious
Leaves opposite, lanceolate to cordate, toothed, prominently 3–5-veined from base; crystals round to elongate
Inflorescence head-, raceme-, or panicle-like
Staminate flower: sepals 4, ± free, green, sharp-bristly; stamens 4
Pistillate flower: sepals 4, ± free, outer 2 < inner 2
Fruit lenticular to deltate, enclosed by 2 inner sepals
Species in genus: ± 50 species: especially temp
Etymology: (Latin: to burn, from stinging hairs)
Reference: [Woodland 1982 Syst Bot 7:282–290]

Introduced

U. urens L.

DWARF NETTLE

Annual 1–6 dm, from slender taproot, monoecious; nonstinging hairs 0 to moderate
Leaf: blade generally < 40 mm, elliptic to ± ovate, base tapered to rounded
Inflorescence generally ± head- (spike-) like, 5–25 mm, often < petiole, with staminate and pistillate flowers
Fruit 1.5–2.5 mm, deltate
Chromosomes: 2n=24,26,52
Ecology: Waste areas, gardens, orchards
Elevation: generally < 3000 m.
Bioregional distribution: California Floristic Province (± except Northwestern California, High Cascade Range)
Distribution outside California: native to Europe