Aha, I remembered it - ragweed. That's the most famous trigger for seasonal allergies, but not the only one. You might want to look up the words 'hay fever' on Wikipedia.com (put it into the search box on the upper right).
You might also look up 'rye grass' on Wikipedia, or on the regular google.com site, in case it is described as a hay fever allergen there.
I happen to have tested very positive to grasses in allergy testing, but I've never reacted to any of them in every day life.