From prescribed bums of northwestern Iowa loess hills and eastern Nebraska tallgrass prairies were used to assess the effects of season of burning and implications for long-term management of grassland ecosystems. Overall forb cover declined most without burning (-22%). Compared to unburned areas, species number on both sites was higher (1-5) with fall burning with the response most pronounced at the loess hills site. The response of species such as false sunflower (Heliopsis heliantboides) suggest that summer and fall burning may do most to encourage seedling germination and establishment. Other species, such as white aster (Aster ericoides) on the tallgrass site and gray goldenrod (Solidapo nemoralis) at the loess hills site, increased in cover with summer or fall burning. Some species showed significant changes irrespective of treatment; in the tallgrass area, porcupine-grass (Stipa spartea) decreased and flowering spurge (Euphorbia corollata) increased. The vegetative responses recorded suggest the likely importance of applying some summer and fail burning, in conjunction with the usual spring burning, to the long-term maintenance of diversity in the tallgrass, loess hills, and perhaps other, grassland ecosystem.