In urban landscapes, however, the ratio is now usually 90-95 percent male, and 10 percent or less female. The result has been a constant rise in total urban pollen loads, and a corresponding rapid rise in the numbers of people affected with pollen allergies. Airborne pollen floats, lands on dry surfaces, and then becomes airborne again with the slightest breeze. Individual pollen grains are so tiny that they can not be seen with the naked eye. To view pollen grains individually requires magnification of 1,000 power or more.
Pollen grains are so small that they easily can pass through the tightest window screens.
The grains of windborne pollen are light and dry and are negatively charged. Mother Nature designed female plants to receive these grains of pollen. Each female tree has thousands of pistillate flowers, each one designed by nature as a highly efficient collector for the airborne male pollen of that particular species. Female flowers stand up in the wind. With their large positively charged surface areas of moist stigmas, they attract, hold, absorb, and ultimately use the male pollen.