The season of fresh grass; spring.
The primary grasses that cause allergies are Timothy, Blue (or June), Sweet Vernal, and Bermuda. Grasses primarily release pollens during the late spring and summer months, except for Bermuda grass which releases pollens in the South year-round.
Grasses are categorized either as cool season or warm season. Warm-season grasses are best adapted to the southern part of the United States. They grow vigorously in the warm summer months, then become dormant, turning brown in cold weather. Warm-season grasses do not thrive in cold climates. Cool-season grasses grow well in the North, at high elevations in the South, and in those parts of the country that have winter snow cover. They grow actively in the cool weather of spring and fall, and slowly in summer heat. With ample water they will remain green the year around. In warm climates a cool-season grass is often seeded over a dormant warm-season grass lawn as a temporary grass during the winter months; it does not survive intense summer heat. You may want to check with your local nursery or county extension service to find out which grass varieties or cultivars grow best in your area.