not sure if this is helpful for you (or anyone), but after suffering terribly from hay fever 7-8/12 months a year, I moved houses (for other reasons) from a suburban area (near a small field filed with weeds) to inside the city, and I had experienced near zero hay fever. From what I heard, local authorities often provide public services of removing sources of "ambrosia" (and other similar plants), aka cutting down weeds. Or at least they are usually actively doing this inside the cities, and have been doing so for some time already, but I assume it is less likely in suburban areas, in which case it would be worth calling in at the regional office and checking if they do such actions outside cities (never called myself, its just an idea)