Annual or perennial, monoecious or dioecious, robust herbs, armed
with stinging hairs. Stem sympodial, zigzag, 5-angled. Leaves alternate,
stipules intrapetiolar, foliaceous; petiolate; leaf blade 3-nerved, margins
dentate or lobed, cystoliths punctiform.
Inflorescence solitary or in axillary pairs, paniculate cymes or spikes,
unisexual; male inflorescence often long,
flowers clustered on rachis of spikes, dichotomous cymes or panicles; female
glomerules lax or dense on rachis of scorpioid cymes, spikes or panicles. Male
flowers: perianth lobes 4 or 5, valvate, filaments inflexed in bud. Female
flowers: perianth lobes 4, 2 or 3 lobes connate into a tube, 2-3 toothed;
staminodes absent; ovary ovoid, stigmas subulate. Achenes large, slightly
oblique, compressed, verrucose. Seeds with thin or without endosperm.