In addition to grass having two growing types, the United States is broken into three types of growing zones: cool zones, warm zones and transition zones. Cool and warm zones will only grow their respective grasses. Transition zones will grow both types of grasses on a seasonal basis.
Warm-season grasses will go dormant in winter in transition zones, but survive until spring. Cool-season grasses may be planted as seed in early fall. They will sprout and grow as warm-season grasses go dormant to provide color through the winter.
Typically summer heat in transition zones kill cool season grasses. For this reason the grass must be reseeded in transition zones yearly.