In Darke County, ragweed begins producing pollen around the week of the fair, and allergies are not relieved until frost kills the plant. Ragweed is difficult, next to impossible to eradicate, because if it is cut off it will grow back in several weeks. There are many varieties of ragweed worldwide, but the one I see in our area is Ambrosia trifida – note the shape of the leaf.
(Goldenrod, also now in full bloom, is harmless and not an allergen.) EH