Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


Short term burial of freshly harvested seed and soil disturbances in agricultural populations of wild poinsettia (Euphorbia heterophylla L.) indicated a very low carry over of seeds into the second season after dissemination. After seeds were buried at 10, 50, 100, and 200 mm in the fall; 4%, 81%, 30% and 1%, respectively, produced seedlings during the following growing season, and only 3%, 1%, < 1%, and 3% of the seeds, respectively, were viable after one year. Soil disturbances (tillage) did not affect seedling recruitment or longevity of wild poinsettia seed. Early planting dates (May 1) of soybeans required 6 weeks of weed-free maintenance to prevent serious reinfestation and subsequent yield reductions in fields with a high agronomic seed bank of wild poinsettia, whereas for late planting dates (June 10) 3 weeks of weed-free maintenance was required. No significant difference in yield was detected between one or two cultivations for either planting date.