Do Not Keep It in the Dark: How Shading and Other On-farm Management Decisions Influence Seed Production and Quality of Asclepias tuberosa L.

Abstract

Demand for butterfly milkweed (Asclepias tuberosa L.) has increased in recent years. However, seed production practices are not well-defined. We partnered with a wildflower seed producer to investigate the effects of weed barrier cloth, plot shading, mature follicle harvest timing, and dry–cold stratification on seed production and germination. Weed cloth had no impact on seed production. However, shading decreased the number of seeds produced by 1.2- to 9.6-fold. Seeds harvested in July and August showed 2.9- and 2.3-fold improvements in total germination and more uniform and rapid germination compared with September-collected seeds. Conversely, seeds exposed to dry–cold stratification displayed a 3.0-fold reduction in the germination rate compared with nonstratified seeds. Our results indicate that the production system significantly impacts seed production and quality of A. tuberosa. Seed producers can use weed barrier cloth to facilitate seed collection from shattering follicles and suppress weeds without a considerable loss of seed production. However, plants should not be grown under conditions of additional shade. Furthermore, high-quality A. tuberosa seeds can be collected earlier in the year, but they should not be subjected to dry–cold stratification.