The tongue of prairie in northeastern Oklahoma is the southernmost portion of the true prairie that extends as far north as Saskatchewan, Canada. This prairie plus much of the western half of the state make up the grasslands, which include the tall-grasses of the east, the mixed grasses of central Oklahoma, and the short grasses of the west. Along the streams and drainages are the extensions of woody species from the post oak-blackjack oak zone.
Native grasses are dominant here but may be of minor allergenic significance. Bouteloua (grama grass) is the only native grass mentioned in the hay fever literature. However, much of the area is being modified and the native grasses are being replaced by species that are greater causes of allergies.
Carya illinoinensis (pecan) and Ulmus americana (American elm) are of major allergenic significance and are restricted to narrow streams and limited bottomland habitats. Quercus virginiana (live oak) occurs in this zone along the North Fork of the Red River and is also an important hay fever tree. Scattered populations of Juniperus pinchotii (red-berry juniper) occur in this zone as well. Approximately 70% of the aeroallergenic species in Oklahoma occur in this zone.
Also, Oklahoma County and Tulsa County are situated along the boundaries of both Zone 3 and Zone 4. Consequently, individuals in these counties will be exposed to allergens from both plant communities.