Urticaceae species can be shrubs (e.g. Pilea), lianas, herbs (e.g. Urtica, Parietaria), or, rarely, trees (Dendrocnide, Cecropia). Their leaves are usually entire and bear stipules. Urticating (stinging) hairs are often present. They have usually unisexual flowers and can be both monoeciousordioecious. They are wind-pollinated. Most disperse their pollen when the stamens are mature and their filaments straighten explosively, a peculiar and conspicuously specialised mechanism.
While the stings delivered by Urticaceae species are often unpleasant, they seldom pose any direct threat to health, and deaths directly attributed to stinging are exceedingly rare; species known to cause human fatalities include Dendrocnide cordata[4][5] and Urtica ferox.[6]
The APG II system puts the Urticaceae in the order Rosales, while older systems consider them part of the Urticales, along with Ulmaceae, Moraceae, and Cannabaceae. APG still considers "old" Urticales a monophyletic group, but does not recognise it as an order on its own.
The fossil record of Urticaceae is scattered and mostly based on dispersed fruits. Twelve species based on fossil achenes are known from the Late CretaceousofCentral Europe. Most were assigned to the extant genera Boehmeria (three species), Debregeasia (one species) and Pouzolzia (three species), while three species were assigned to the extinct genus Urticoidea.[7] A Colombian fossil flora of the Maastrichtian stage has yielded leaves that resemble leaves of the tribe Ceropieae.[8] In the Cenozoic fossil leaves from the YpresianAllenby Formation preserve distinct trichomes, and have been attributed to the Tribe Urticeae in the fossil record. The leaves had originally been identified as Rubus by earlier workers on the Eocene Okanagan Highlands, but Devore et al (2020) interpreted the preserved hairs along the stem and major veins as stinging trichomes, rather than simple hairs or thorns.[9]
Myrothecium leaf spot, a fungal disease caused by Myrothecium roridum which affects plants throughout the Urticaceae, as well as other angiosperms[24][25]
^Else Marie Friis; Peter R. Crane; Kaj Raunsgaard Pedersen (18 Aug 2011). Early Flowers and Angiosperm Evolution. Cambridge University Press. ISBN978-0-521-59283-3.
^Treiber, E. L.; Gaglioti, A. L.; Romaniuc-Neto, S.; Madriñán, S.; Weiblen, G. D. (2016). "Phylogeny of the Cecropieae (Urticaceae) and the evolution of an ant-plant mutualism". Systematic Botany. 41 (1): 56–66. doi:10.1600/036364416X690633. S2CID28743975.
^Kim C, Deng T, Chase M, Zhang D-G, Nie Z-L, Sun H. (2015). "Generic phylogeny and character evolution in Urticeae (Urticaceae) inferred from nuclear and plastid DNA regions". Taxon. 64 (1): 65–78. doi:10.12705/641.20.{{cite journal}}: CS1 maint: multiple names: authors list (link)
^Treiber EL, Gaglioti EL, Romaniuc-Neto S, Madriñán S, Weiblen GD. (2016). "Phylogeny of the Cecropieae (Urticaceae) and the evolution of an ant–plant mutualism". Systematic Botany. 41 (1): 56–66. doi:10.1600/036364416X690633. S2CID28743975.{{cite journal}}: CS1 maint: multiple names: authors list (link)
^Deng Tao; Kim C; Zhang D-G; Zhang J-W; Li Z-M; Nie Z-L; Sun H. (2013). "Zhengyia shennongensis: A new bulbiliferous genus and species of the nettle family (Urticaceae) from central China exhibiting parallel evolution of the bulbil trait". Taxon. 62 (1): 89–99. doi:10.1002/tax.621008. JSTOR24389315.
