I think the best way to answer when grass pollen allergy season comes is to outline the growth and reproductive stages that the cool-season types of lawn grasses undergo annually. The time of year that you have to worry is during the flowering part of the cycle.
As the snow recedes in the North in early spring, the cool-season grasses start to grow actively once again, pushing up green shoots. From these shoots, flower stalks will emerge at some time in May. Flowers (inflorescences) will follow. The average person may not think of the grass in a lawn as ever "flowering" and may speak, instead, of the grass "going to seed," but it amounts to the same thing: grass must first flower before it can go to seed.
Reproductive activities occurring in these flowers will be a factor for sufferers of grass pollen allergy mainly for 3 months in the North: May-July. Kentucky bluegrass is one of the worst offenders among the cool-season grasses.
"Cool-season grasses" are called that because they grow most actively in the spring and fall in the North, when the weather is neither hot nor cold, but "cool." They go dormant at some point in the summer (without a lot of watering on your part or the use of an automatic irrigation system), to cope with weather that's too hot and dry for them. It's like "taking a breather." In autumn they will perk back up again, but the fall lawn puts more energy into such things as storing nutrients for winter.
A well-maintained lawn won't contribute to problems with grass pollen allergies, because flower stalks are mowed down before flowers can develop. Sufferers from grass pollen allergies can blame their troubles on wild grasses and grass in lawns that are not mowed regularly.
If you suffer from grass pollen allergy and want to try to minimize exposure, you can:
- Mow often: The recommended mowing height is when the grass is 3 to 3 1/2 inches tall.
- Wear a face mask when working in the yard May-July, in case your neighbors are less fastidious and allow their grass to bloom.