In contrast to bahiagrass, guineagrass and bermudagrass had significant increases in DM harvested under extended daylength only at the subtropical site (south Florida). The increase in DM with extended daylength for guineagrass and bermudagrass that was present in south Florida was not observed at lower, tropi- cal latitudes (Puerto Rico and St. Croix; P > 0.52). The failure to alleviate in guineagrass and bermudagrass at least part of the decline in growth during the short-daylength period with extended daylength implies that there are other factors involved in growth regulation of these two grasses.