Any plant whose foliage is covered with stinging, mildly poisonous hairs, causing an instant rash. • Especially, most species of herb genus Urtica, stinging nettles: • Most, but not all, subspecies of Urtica dioica (common nettle), • Urtica incisa (Australian nettle); • wood nettle (Laportea canadensis); • bull nettles and spurge nettles (Cnidoscolus spp.): • bull nettle, spurge nettle (Cnidoscolus stimulosus) • Texas bull nettle (Cnidoscolus texanus), • bull nettle (Cnidoscolus urens), • nettle trees or tree nettles: • Various species of the genus Dendrocnide • Various species of the genus Dendrocnide: • small-leaved nettle (Dendrocnide photinophylla). • scratchbush (Urera baccifera) • tree nettle (Urtica ferox); • rock nettles (Eucnide spp.); • Certain plants that have spines or prickles: • ball nettle (Solanum carolinense); • bull nettle, silver-leaf nettle, white horse-nettle (Solanum elaeagnifolium); • western horse-nettle, robust horse-nettle (Solanum dimidiatum); • horse-nettle (Solanum rostratum); • hackberries (Celtis spp.). • Certain non-stinging plants, mostly in the family Lamiaceae, that resemble the species of Urtica: • dead nettles, dumb nettles (Lamium spp.), particularly Lamium album, white nettle; • false nettles (Boehmeria spp., family Urticaceae); • flame nettles or painted nettles (Coleus spp.); • hedge nettles (Stachys spp.); • hemp nettles (Galeopsis spp.); • horse nettle Agastache urticifolia, • nilgiri nettles, Himalayan giant nettles (Girardinia diversifolia, family Urticaceae spp.). • Loosely, anything which causes a similarly stinging rash, such as a jellyfish or sea nettle.