THE BIOLOGY OF CANADIAN WEEDS.: 21. Urtica dioica L.

Abstract

A summary of biological information on Urtica dioica L. ssp. gracilis (Ait.) Selander (American stinging nettle) and ssp. dioica (European stinging nettle) is presented. American stinging nettle is widespread throughout Canada, while European stinging nettle is confined to a few disturbed habitats in Eastern Canada. American stinging nettle is often weedy in nutrient-rich soils such as are normally associated with cultivated row crops, old pastures, farmyards, irrigation canals, drainage ditches, orchards, and open woodlands. Airborne pollen of Urtica dioica, shed in large amounts, in known to cause hay fever. The stinging emergences (needles) of both subspecies produce a painful sting to the human flesh.