Increasing the germination potential of dormant seeds in a population over time generally requires afterripening. Research was conducted to study the relationship between temperature and seed moisture content on afterripening of dormant leafy spurge seeds. Germination of nonafterripened seeds was 59 and 36% after 21 d for the Harwood and Fargo populations, respectively. Germination of 85 to 87% and 58 to 62% was obtained for the Harwood and Fargo populations, respectively when afterripened for 12 to 24 wk under the most effective conditions of 30 C and 2.6% seed moisture; increasing the afterripening temperature to 45 C did not increase germination. Germination decreased slightly at 30 C as the seed moisture content increased to 5.6%, but germination still exceeded that of nonafterripened seeds. Afterripening at 30 C with a seed moisture content of ≥9% greatly decreased germinability due to seed ageing. A temperature of 5 C was effective for afterripening when the moisture content was 3.3%, but germination was still slightly less than for the low moisture content seeds afterripened at 30 C. Afterripening seeds with 6 to 13% moisture at 5 C generally did not increase germination compared with the control, but did not result in seed ageing.

Nomenclature: Leafy spurge, Euphorbia esula L. EPHES