Pines pollinate profusely, contributing large numbers to pollen counts, and presenting often visible layers across streets and car windows when in season. However, they are rarely considered a particularly allergenic pollen. <a href="http://www.pollen.com" target="_blank">Pollen.com</a> lists these as predominant pollen only when other more important types are lacking.
Pines are usually evergreen, and have needlelike, or linear leaves arranged in spirals with flattened cone scales. The mature cones are woody and the seeds are winged or wingless. These trees have a distinct scent, which is often simulated in cleaning products and air fresheners.
Pine grains are large due to their sacs or bladders, which make them one of the easiest pollen grains to identify. These sacs also allow them to be carried great distances by the wind. Among winged grains, the body is subspheroidal to broadly ellipsoidal. The bladders are generally reticulate or occasionally smooth.
Pollen grains vary in size from 40-85 micrometers.
The shaded areas on the map indicates where the genus has been observed in the United States.
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