Release of Postsenescent Dormancy in Leafy Spurge (Euphorbia esula) by Chilling

The growth and development of leafy spurge (Euphorbia esula L. #3 EPHES) collected during postsenescent dormancy and grown in the greenhouse was increasingly stimulated by chilling treatments longer than 14 days duration at 0 to 6 C. Production of stems with flower buds, primary flowers, and secondary flowers was greater in plants chilled for 42 days or more. The effects of chilling on total number of stems, number of strictly vegetative stems, or number of stems with vegetative branching were not significant. The height of the tallest stem per pot was influenced by chilling longer than 42 days. Growth rate also increased as a function of chilling duration. Based on our findings, we believe that there is little possibility that any significant growth can occur in the postsenescent period because of the prevailing climatic conditions found in areas of leafy spurge distribution in North America.