The basic unit of forage production is a tiller, which is composed of leaf blades and leaf sheaths, stem, and sometimes a seedhead. Most forage grasses will produce between 5 and 10 leaves per tiller. The last leaf to emerge is the flag leaf. The flag leaf precedes the emergence of the seedhead and is recognized by its peculiar orientation, generally parallel to the ground. However, not all tillers become reproductive and produce a seedhead.
Seedhead production varies from species to species and seasonally within species.
Tall fescue makes a good example. Most spring growth tillers, in response to temperature and day length, produce seedheads. Fall growth tillers generally remain vegetative. In some cases there are also varietal differences in seedhead production within a species, as common verses Coastal bermudagrass. New tillers originate from basal buds, a form of specialized plant tissue.