FACTORS AFFECTING SEED PRODUCTION IN TRIFOLIUM MEDIUM

Abstract

Seed production studies in field nurseries revealed that the bumble bee is the most important pollinator of zigzag clover (Trifolium medium L.) and that seed-setting is directly correlated with the frequency of their visits. The long corolla tube of this clover precludes its pollination by the honey bee. Nectar secretion is approximately the same in amount and concentration as in red clover, the most important competing species for pollinators.T. medium has a high chromosome number (2n = 80) but meiosis is regular and a high percentage of good pollen is formed. Improved seed-producing strains were established by combining high-seed-producing plants in polycross nurseries. Seed yields are increased by cutting back the plants in late May. Seed yield appears to be genetically controlled.The species occurs in isolated areas in uncultivated pastures in Eastern Canada. All plants within each area examined are intersterile but cross readily with plants from other sources. This suggests that each area may have originated from a single seedling which spread by stolons.