"Weed pollens" refers to the tiny particles released by certain plants known as weeds. These pollen grains are carried by the wind and have the potential to trigger allergies in some people. Full definition
Symptoms that occur during the fall months may indicate an allergy to ragweed or other weed pollens. (babycenter.com)
In past years, the fall pollen season has been less intense, characterized by weed pollen, predominantly ragweed. (sciencedaily.com)
For example, in the Middle Atlantic states, tree pollen is the culprit from February through May, followed by grass pollens from May through June, and weed pollens from August through October. (health.com)