Biologist Blog Galls on Trees
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You may have noticed these circular objects on the ground at the base of trees on your walk outside . These are completely harmless galls . They are formed when plant tissue is exposed to foreign objects such as fungi , insects , bacteria , or nematodes . Insects are the most common culprit to these forming on the trees . Galls are formed on the roots , flowers , buds , bark , and leaves . The most common gall seen on our oak trees are called Oak Plum Galls . When they ’ re forming on the trees , they resemble a soft green ball about the size of a grape . Once they harden , they fall to the ground where the insect exits . Pictured below is a gall found out back on the property .
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