May

The spring tree pollen season winds down in May. The beginning of May still finds some oak, mulberry, and other April pollen types still in the air. Black walnut, hickories, and Osage orange which began to pollinate in mid to late April, typically reach peak levels in May. There are several species of hickory in eastern Oklahoma including pecan (Carya illinoensis). Also, grass pollen is in the air during May as many of the native grasses are flowering. The peak of the grass pollen season occurs in late May, but many grasses continue to pollinate all summer and into the fall. Weeds that are pollinating in May include sedges (Cyperaceae), dock (Rumex sp) and nettle (Urticaceae).