Rye Grass

( lat. Lolium )

Kingdom: Plantae
Order: Cyperales
Family: Poaceae
Genus: Lolium

Plant Allergy Overview



Pollen Season

Spring to Fall





Allergy Information

This is one of the more significant grass types in terms of allergy. Abundant pollen shed can cause severe pollinosis problems in all regions of the U.S.

Genus Details

The rye grass genus has short-lived perennial, biennial, and single-stemmed annual species. This grass is widely used in lawns, pastures as a forage, roadsides and waste areas. Perennial types grow in tufts or mats. Flat or slightly rolled (inward) leaf blades have a smooth surface and grow 1-10 inches long. Flowers are located on stalks 2-6 inches tall. Flowering occurs in June-August. The majority of the pollen comes from the grass found in patures, hay fields and wild areas, since the plants must usually be more than 1 foot tall to flower.

Pollen Description

Grains are spheroidal to ovoidal, sometimes elliptical. The exine is thin and the surface is granular to finely reticuloid. Poaceae apertures are 1-porate, with the pores usually circular to ovoidal.

Grains are 22-122 micrometers in diameter.

Genus Distribution

The shaded areas on the map indicates where the genus has been observed in the United States.

- Native, observed in a county 
- Introduced, observed in a county 
- Rarely observed

Species in Rye Grass Genus

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