Annual Bluegrass (Poa annua)

Kentucky bluegrass is the most common turfgrass in the United States. Its use as a turf grass in Arizona is limited to the cooler parts of the state, typically at elevations about 5000 ft, although it may be used in some aggressively maintained golf courses at lower elevation. Annual bluegrass is a weedy variety that invades Bermuda grass lawns and fields in Arizona desert communities during the fall through spring. Birds and small animals eat the seed of the grass providing widespread distribution. Bluegrass pollen is highly allergenic and cross reacts with other cool weather grasses such as Rye grass and Timothy grass. It likes cool, wet conditions and will proliferate and take over lawns and sport fields if we have a rainy winter.

Johnson Grass

Johnson Grass flower

Johnson Grass is found in washes, along road sides and other areas where there is enough water.  Although it is an allergenic grass,  pollen counts in the Phoenix area tend to be low because of it’s sparse distribution.   It pollenates May through October.

Bermuda grass (Cynodon dactylon)

Bermuda Grass flower

Bermuda Grass flower

Because of it’s resistance to heat and drought, Bermuda grass is well suited for Arizona and the desert southwest.  Common Bermuda is propagated by seed and produces significant amounts of pollen. It is used extensively in school sports fields, parks, golf courses, and green belts.  Hybrid Bermuda grasses such as Tif and Midiron, are the result of mating common Bermuda grass with African Bermuda grass resulting  in a plant with a finer leaf texture and which does not produce pollen or seed.    These hybrid varieties are used in many home lawns and smaller fields.     In 1994, Phoenix passed the Airborne Pollen Ordinance which requires that Bermuda grass lawns be kept short to prevent pollen-producing seed heads (see picture)  from forming.  It pollenates May through October