Urtica L.

Scientific Description

Common name. Nettles. Family Urticaceae.

Habit and leaf form. Herbs. Annual, or perennial; plants with neither basal nor terminal concentrations of leaves. Young stems tetragonal. Mesophytic. Leaves small to large; opposite; decussate; petiolate; simple. Leaf blades entire; elliptic, or ovate, or triangular; pinnately veined, or palmately veined; cross-venulate; cuneate at the base (to truncate). Leaves with stipules. Stipules interpetiolar, or intrapetiolar; free of one another (and lateral), or concrescent (and intrapetiolar). Leaf blade margins entire (subentire, very rarely), or dentate (to incised). Leaves without a persistent basal meristem. Leaf anatomy. Urticating hairs present. Stem anatomy. Secondary thickening developing from a conventional cambial ring.

Reproductive type, pollination. Fertile flowers functionally male and functionally female (usually), or functionally male, or functionally female. Unisexual flowers present. Plants monoecious, or dioecious (rarely). Male flowers with pistillodes (pistillode cupuliform, translucent). Anemophilous. Pollination mechanism conspicuously specialized.

Inflorescence and flower features. Flowers aggregated in ‘inflorescences’; in fascicles (or clusters). The terminal inflorescence unit cymose. Inflorescences axillary; paired inflorescences in interrupted spikes or panicles, inflorescences unisexual or bisexual; with involucral bracts, or without involucral bracts. Flowers pedicellate, or sessile to subsessile; bracteate, or ebracteate; minute, or small; regular; 4 merous. Hypogynous disk absent. Perianth sepaline; 4; 1 -whorled; free, or joined; persistent; accrescent, or non-accrescent. Calyx present; (the perianth being thus interpreted) 4; 1 -whorled; polysepalous, or gamosepalous (male flowers connate at the base); imbricate, or valvate; unequal but not bilabiate, or regular (one opposite pair larger than the other in female flowers); persistent; accrescent, or non-accrescent. Fertile stamens present, or absent. Androecial members definite in number. Androecium 4. Androecial members free of the perianth; all equal; free of one another; 1 -whorled. Androecium exclusively of fertile stamens. Stamens 4; all more or less similar in shape; isomerous with the perianth; oppositisepalous; inflexed in bud (uncoiling elastically); filantherous. Anthers dorsifixed; dehiscing via longitudinal slits; introrse; tetrasporangiate. Fertile gynoecium present, or absent. Gynoecium ostensibly 1 carpelled (i.e. with no obvious evidence of more than one carpel). The pistil 1 celled. Carpels reduced in number relative to the perianth. Gynoecium monomerous (ostensibly), or syncarpous (theoretically); of one carpel (at least, usually with no evidence of syncarpy), or synstylovarious to eu-syncarpous (theoretically); superior. Carpel (if treated as monomeric) shortly stylate, or non-stylate; apically stigmatic; if the gynoecium is considered monomerous) 1 ovuled. Placentation basal. Ovary unilocular; (if the gynoecium is considered pseudomonomerous) 1 locular. Gynoecium non-stylate, or stylate. Placentation if recognised as syncarpous, basal. Ovules in the single cavity 1; funicled, or sessile; ascending; non-arillate; orthotropous to hemianatropous.

Fruit and seed features. Fruit non-fleshy. The fruiting carpel indehiscent; (if the gynoecium is considered monomerous) an achene, or nucular. Fruit indehiscent; (if the gynoecium is considered syncarpous) achene-like, or a nut; 1 seeded. Seeds scantily endospermic, or non-endospermic. Endosperm oily, or not oily. Cotyledons 2. Embryo straight.

Geography, cytology, number of species. World distribution: Worldwide in temperate and warm temperate regions, including Australia. Native of Australia, or adventive. Not endemic to Australia. Australian states and territories: Western Australia, South Australia, Northern Territory, Queensland, New South Wales, Victoria, Australian Capital Territory, and Tasmania. Eremaean Botanical Province and South-West Botanical Province. A genus of 100 species; 2 species in Western Australia; 0 endemic to Western Australia.

Economic uses, etc. Nettles constitute quite palatable greens.

Etymology. From the Latin for "nettle"; from the word for "to burn, sting". The power to sting lasts even in dried plants. W. T. Stearn relates that when Linnaeus' herbarium was being photographed in 1941 as a war precaution, the photographer was stung on the arm-raising a blister-by a specimen dried and mounted some 200 years earlier.