Interest in the use of native plants in home gardens and cultivated landscapes has increased in recent years. Use of native plants is partly a result of the interest in creating additional habitat for plants and the community of animals that depend on them. Few studies have examined the effect of the environment in which native plants grow, whether in native populations or in home gardens, where they may have greater access to needed resources. Cold stratification of seeds of many native species is recommended by commercial suppliers of those seeds to promote enhanced germination. Recommended stratification periods differ between suppliers. In this study over two years we examined differences in seed mass, germination, and early growth of seedlings of Asclepias incarnata using seeds collected from plants growing in wild populations and gardens. In both years we compared seeds from a native population and at least one garden population while controlling length of the stratification period. In year 2 we studied seeds from plants from a native population, from a garden using commercially acquired plants of Pennsylvania ecotypes, and from a second garden with milkweed of unknown provenance.
Results/Conclusions
In year 1 of this study, seeds from native swamp milkweed populations were larger than those from garden plants. With a cold stratification period of 10 days germination success of garden collected seeds was significantly greater than that of wild collected seeds but was less than 50%. Despite low germination success, the large seeds from wild populations yielded larger seedlings. In year 2, seeds were cold stratified for 45 days to test whether seed germination would be enhanced by longer pretreatment. Preliminary results suggest that germination success of garden plants is increased by the longer pretreatment and success of native collected seeds remains relatively low compared with garden plants similar to findings from year 1.