They shed considerable amounts of pollen, which presents a significant challenge to allergy sufferers. The pollen is commonly allergenic, and may cause severe reactions.
Oaks are a particularly large genus, with various species growing throughout the U.S. They are commonly found in residential areas, as well as parks, and remote forests. The trees are large, reaching heights of 150 feet. The plants contain both male and female flowering parts, meaning they produce pollen, and can be pollinated, too, either by themselves, or by other plants. The fruit is an acorn, which provides a staple in the diet of many small animals.
The pollen grains are spheroidal or oblately flattened and triangular in outline. They are tricolpate with long and narrow colpi.
Pollen grains are usually 24-38 micrometers.
The shaded areas on the map indicates where the genus has been observed in the United States.
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