Grass Pollen: Allergy, Types & Season

Grass pollen is the late-spring and summer act of the pollen year, and the grass index on every Pollen Atlas city page is built from it. This page explains what grass pollen is, which grasses produce it, and why grass season runs on two different clocks in the North and the South.

What is grass pollen?

What is grass pollen? It is the pollen of the true grasses — pasture, lawn and meadow species that flower through late spring and summer. Most kept lawns are cut before they flower, so the grass pollen in a city's count comes mainly from unmowed edges, meadows, pasture and roadsides. The types of grass pollen that matter most are the six grasses below, and they split into two allergen families that behave very differently.

The grasses in the count

• Bermuda grass (Cynodon dactylon) — warm season, spring through fall in hot climates; the grass allergen of the South and Southwest. Bermuda grass pollen guide
• Timothy grass (Phleum pratense) — late spring to early summer, May to July; the classic hay-fever grass of northern pastures and of northern Europe. Timothy grass pollen guide
• Ryegrass (Lolium) — spring to early summer, April to June; lawns and pastures nationwide and the Pacific Northwest's grass-seed valleys. Ryegrass pollen guide
• Kentucky bluegrass (Poa pratensis) — late spring, May to June; the default cool-season lawn grass of the northern United States. Kentucky bluegrass pollen guide
• Johnson grass (Sorghum halepense) — warm season, May into fall; fields, roadsides and ditch banks across the South and Southwest. Johnson grass pollen guide
• Fescue (Festuca / Schedonorus) — late spring to summer, May to July; the pasture and lawn grass of the American transition zone. Fescue pollen guide

Grass allergy: one family, two allergies

Grass pollen is the late-spring and summer act. The northern pasture grasses share their allergens and are usually reported together; the warm-season grasses — Bermuda, Johnson — are separate allergies of the South and Southwest. A northern grass allergy therefore usually means some reaction to the whole shared set — timothy, ryegrass, bluegrass, fescue — while grass allergies in hot climates often trace to Bermuda grass specifically, a grass pollen allergy of its own with a much longer season. As with most pollens, the pattern in sensitive people is sneezing, a runny or blocked nose, and itchy, watery eyes, and any pollen can aggravate asthma. If your grass-season pattern does not match the counts, a specialist can help separate the two families — you can find an allergist in the Pollen Atlas directory.

When grass pollinates

Grass pollen season opens in late spring — the northern grasses flower from May into July — while the warm-season grasses run from spring through fall where winters are mild. The full calendar is in the grass pollen season guide. Follow today's grass index on the Phoenix pollen count page, where Bermuda grass leads, and the Spokane pollen count page, where timothy leads — and compare cities in the city rankings and on the pollen heatmap. The other family reference pages are tree pollen and ragweed.