Airborne pollen survey for Lincoln, Nebraska. III. Weeds.

Pollen counts in 1988, 1989, and 1990 revealed 16 weed pollen types. The weed pollination season in Lincoln extends from March through October. Very low amounts of pigweed-type and nettle pollen appear in April. Dock pollination begins in May. June has the greatest diversity of weed types and moderately high total counts (highest total June counts ca. 300 grains/m3). July is low in both diversity and absolute numbers of pollen grains (highest total July counts ca. 35 grains/m3). In early August pollen counts begin to rise with the primary pigweed-type pollination season and the first ragweed pollen. Ragweed pollen peaks in the last week of August and first week of September with more than 460 ragweed grains/m3 and total counts of more than 780 gr/m3.