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Sheoak Trees, also called Australian Pine Trees, are trees in the genus Casuarina of the sheoak family. The genus contains 14 species, generally from the southern hemisphere. Although these trees have needle-like leaves visually resembling pine trees and fruits vaguely resembling pine cones, the sheoak family is most closely related to the beech (and oak), birch, and walnut families.
Sheoak trees are a major cause of hay fever. They typically bloom from about November through March, so if you suffer from hay fever during those months, sheoak trees could be the culprits.
River Sheoak (Casuarina cunninghamiana) is an evergreen tree from Australia and New Guinea. It usually grows 50 to 110 feet tall. These trees are either male or female, so they do not produce seedlings unless there are both male and female trees in the area. Only the male trees produce pollen, but male River Sheoak trees are ranked 10 out of 10 on the Ogren Plant Allergy Scale, indicating that they tend to cause very severe hay fever. It is planted in Campbell Park, Dave Douglass Park, and Woodland City Cemetery.
Horsetail Tree (Casuarina equisetifolia), also called Beach Sheoak, is an invasive weed from Australia, New Guinea, India, and Southeast Asia. It usually grows 20 to 40 feet tall. Its winged seeds are dispersed both by wind and by birds. Male and female flowers are borne on the same tree. Horsetail Tree is ranked 10 out of 10 on the Ogren Plant Allergy Scale, indicating that it tends to cause very severe hay fever. It is planted in Ralph Harris Park and as a street tree on 5th Street and on the roundabout facing Beamer Circle Park. In fact, the Urban Forest Resource Analysis published by the City of Woodland in 2018 indicated that the city was knowingly and intentionally maintaining 16 of these invasive weeds in Woodland.