Seeding date affects seed and biomass yield of Silphium integrifolium Michx. (silflower)

Abstract

Silphium integrifolium Michx. (silflower [Asteraceae]) is an emerging perennial oilseed and biomass crop with potential to supply ecosystem services, but optimum seeding dates for establishment are unknown. Our objective was to determine the effect of seeding dates from late summer to spring on establishment, biomass, and grain yield of wild and improved silflower populations. Germination was low, but plants established for all seeding dates, indicating that seed sown in the early fall (September and October) germinated and overwintered, and seed sown in late fall (November and December) overwintered as seeds, germinating in the following spring. Spring-sown (March through June) seed germinated without stratification. While this shows many planting date options for successful germination, only September planting dates produced acceptable seed and biomass yields within one full growing season of sowing. Spring seedings resulted in no grain yield in the following summer, confirming that vernalization was required for grain production. For use in Midwest cropping systems, the establishment of silflower at seeding dates early in September is currently recommended, but additional studies should consider summer planting dates, seed pretreatments, and the effects of the duration of the vegetative stage on plant traits such as drought resistance in addition to first-year seed and biomass production.