Birds do it, bees do it, and so do plants. They all reproduce. Pollen grains, the stuff that makes you sneeze, are simply the microscopic male reproductive cells released by trees, grasses, and weeds. A pollen grain, similar to the male sperm, contains half the genetic material needed for reproduction. Pollination occurs when pollen grains are released by one plant and carried by the wind to another similar plant in order to fertilize it. (Large pollen is also carried via birds and insects, but these don't cause you to sneeze.)
Love in the air elicits a romantic response from plant life, but for some forms of human life (i.e., allergy sufferers) it guarantees an allergic response. The terrible trio of tree pollens, grass pollens, and weed pollens causes misery for allergy sufferers, especially from spring to fall. Unlike the pollens from flowers and shrubs, this trio releases pollens that are light, numerous, and easily transported by the breeze.
You can get an idea of the kind of pollen that most troubles you simply by observing when your symptoms start and when they wane. Tree pollens, for instance, herald the beginning of the allergy season. Although pollen seasons vary by geographic region, those stately, shade-producing trees we love -- box elder, chestnut, ash, walnut, cottonwood, oak, elm, maple, willow, cedar, sycamore, and more -- typically send out showers of pollen from March through May. (In Texas, however, cedar pollen season is January!) Thankfully for aching noses and irritated lungs, tree pollination season is short-lived.
Just when you thought it was safe to venture outside, out pop grass pollens. More common than tree pollens, grass pollens generally reach their peak from mid-May to mid-July, although the timing varies by geographical region. In California and Florida, for instance, grass pollen season is from February through October. Grass pollens are larger than tree pollens (often you can see them in the air), and they affect the nose and eyes most drastically. There's no escape, as the wind transports grass pollens to all ends of the earth. With 9,000 grass species worldwide, it's hard to name all, but popular pollinators in North America include barnyard grass, Bermuda grass (in southern areas), bluegrass varieties, corn, fescue, ryegrass (cultivated lawn grass), cultivated wheat, and wheat grass.
In the next section, we will talk about a different kind of pollen that can affect you just as much as grass pollen. The offender? Weed pollen.