The perennial sunflower Silphium integrifolium Michx. (Asteraceae), also known as silflower, is a prospective dual-purpose forage plus grain crop. Pre-flowering biomass harvest for animal feed and the subsequent delay in plant growth and anthesis has the potential to benefit seed yield and/or offset yield loss from native pests, such as the native North American Eucosma giganteana (Lepidopera: Tortricidae). The aim of this study was to develop a cropping technology for silflower to (A) balance forage and grain production and (B) minimize seed loss. Silflower produced high-quality forage, but biomass harvest in early spring reduced same-season seed production by 45%. Despite significantly delaying flowering, forage harvest alone did not effectively reduce Eucosma colonization, although treating plants with the insecticide permethrin did reduce colonization. Our results do not support the proposal that S. integrifolium could be profitably harvested for both high quality forage and as an oilseed grain within the same season. Nevertheless, our findings suggest the possibility of developing a strategy of alternating between forage or seed production, depending on their differential economic values. The choice between harvesting biomass vs. seed could be made much later in the season for this perennial crop than the choice of planting an annual forage vs. annual grain crop.

Thinopyrum intermedium (c.n. intermediate wheatgrass), marketed under the trade name Kernza, is a promising species for perennial grain production based on seed size, ease of threshing, resistance to shattering, and grain quality. Although numerous generations of breeding for seed yield have been completed, the impact of selection on non-target traits is unknown. Here, we evaluated structural and functional changes brought about by selection for seed yield over a sequence of nine selection cycles (C0 to C9). In two experiments under semi-controlled environmental conditions, we compared gas exchange (A, E, gs, and A/Ci curves), leaf and root morphology, and the structure of seedlings from 10 generations. We found that the selection for yield throughout cycles indirectly changed the leaf structure (leaf size, leaf thickness, and leaf anatomy) and physiology (carbon acquisition and transpiration per unit area), with later cycles showing larger leaves with higher rates of CO₂ assimilation and transpiration. Changes in root structure followed similar trends: selection resulted in longer, more branched, and finer roots. These changes in non-target traits are linked to resource-use strategies and to ecosystem services provided by Kernza. Understanding how the domestication of perennial grains impacts non-target traits will aid in the design of integrated breeding programs for Kernza and other perennial grain crops.