A N F Keys
1 Plants with stinging hairs; leaves opposite
2 Perennial, 100−400 cm tall; the largest leaves 100−200 mm long; inflorescences about as long as their subtending leaf; dioecious .. Urtica dioica subsp. holosericea [pics]
2' Annual, < 80 cm tall; the largest leaves < 70 mm long; inflorescences only as long as or even shorter than the petiole of their subtending leaf; monoecious
3 Blades serrate; stinging hairs present along lower veins of blade and on peduncle and calyx of pistillate flower .. Urtica urens [pics]
3' Blades crenate; stinging hairs absent on lower surface of blade at least above midblade and on inflorescences .. Hesperocnide tenella [pics]
1' Plants without stinging hairs; leaves alternate
4 Stems spreading or decumbent, not rooting at nodes; leaves petiolate, ca. 10 mm long; flowers clustered .. Parietaria hespera [pics]
4' Stems creeping, forming a mat rooting at nodes; leaves nearly sessile, ca. 4−5 mm long; flowers solitary .. Soleirolia soleirolii [pics]
1 Perennial, 100−400 cm tall; the largest leaves 100−200 mm long; inflorescences about as long as their subtending leaf; dioecious .. Urtica dioica subsp. holosericea [pics]
1' Annual, < 80 cm tall; the largest leaves < 70 mm long; inflorescences only as long as or even shorter than the petiole of their subtending leaf; monoecious .. Urtica urens [pics]
The text of the above keys used with permission from
A Naturalist's Flora of the Santa Monica Mountains and Simi Hills, California
© Copyright
Barry A. Prigge and Arthur C. Gibson
2013