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The Causes of Pollen

In the spring and fall, many people suffer from red, itchy eyes, runny noses and various other symptoms associated with the release of pollen from plants. The pollen that is released into the air and spread by the wind is the culprit for most of the pollen that triggers allergic reactions -- although brightly colored flowers also produce pollen that is carried by insects, birds and moths.

Tree Pollen
- According to emedtv.com, only about 100 types of trees are known to produce pollen that causes allergic reactions. Trees release their pollen as early as January in southern parts of the United States, and as late as June in the northern states. Some people have tree-specific allergies -- and in some tree species such as ash, box elder, cottonwood, date and phoenix palm, red and silver maple, poplar and willow, only the male trees produce pollen. Trees rely on the wind to spread their pollen to other trees, so they produce excess pollen to increase the chances that fertilization will occur.
Floral Pollen
- Flowers in your garden also produce pollen, but the difference between them and trees and leafy plants is that they do not broadcast pollen over a large area. Instead, they enlist the help of insects, birds and moths to help carry their pollen to other flowers of the same species. This vastly reduces the amount of energy they need to expend making pollen since a small amount is necessary. Insects and plants have co-evolved to depend on each other, with plants needing insects for reproduction and insects needing plants for food.
Timing
- Different plants release their pollen at different times of the day as well as different seasons of the year. For instance, trees release pollen in the springtime, and between 5:00 and 10:00 in the morning. Grasses, on the other hand, pollinate later in the spring and early summer. When conditions are chilly and wet, plants tend to not release much pollen since it will be washed away by rain water, thus wasting an opportunity to pollinate. Plants will release more pollen during dry, windy conditions when pollen will not get hung up on obstacles on its way to other plants.
Coniferous Pollen
- Coniferous trees have needles and pine cones to collect and distribute pollen. Pine trees produce very large pollen granules, though their waxy nature means that it is less allergenic than other types of pollen. Female pine cones release sap so that passing pollen will stick to it, and their seeds are produced inside the cones. Pine pollen is very resilient, as sciencedaily.com reports that it can travel upward of 1,800 miles, being exposed to harmful ultraviolet radiation and rain droplets while still being able to germinate.

Nature