THE BIOLOGY OF CANADIAN WEEDS.: 85. Euphorbia cyparissias L.

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Abstract
A review of the biology of Euphorbia cyparissias L. (cypress spurge) is presented. A key is provided for identifying those members of the Esula complex which occur in Canada. Cypress spurge is more abundant in eastern than western Canada. In North America, two cytotypes are found, namely a sterile diploid (2n = 2x = 20) and a fertile tetraploid (2n = 4x = 40); however, in Europe there is also a fertile diploid. Sterile diploids do not set seed. Fertile diploids have little or no capacity for vegetative reproduction. Fertile tetraploids have abundant seed set; in addition, they produce more shoots than the sterile diploids. Consequently, the tetraploids are the most weedy. Cypress spurge is commonly found on limestone or gravel substrates. Methods for achieving control are presented.Key words: Euphorbia cyparissias L., cypress spurge, graveyard weed, weed biology