The Biology of Canadian Weeds. 147. Onopordum acanthium L.

The article presents the biology of the Canadian weed Onopordum acanthium L. It is described as a biennials whose seedlings consist of a relatively large, fleshy and sparsely branched which is surmounted by a pair of 1.25-2 cm long, glabrous entire cotyledons that are pale green with whitish venation. It refers to Onopordum acanthium as a strongly competitive species that infests small grain fields in Nevada and northeastern California. It indicates its response to herbivory such as mammals and birds, disease and higher plant parasites.