Trees pollens cause symptoms mainly in the spring, when trees pollinate in temperate climates. This usually begins in mid-February (depending on the weather) with Cedar. In the Columbus area, tree pollen counts are highest in April and May, and taper off in early June.
Here are the trees that most commonly cause allergy symptoms in this area, with links to the excellent Greer Labs website showing details of the plant.
Black Walnut pollen