Knowledgebase
Strange growth on tree branches in front yard #800820
Asked July 12, 2022, 7:58 PM EDT
We live in Denver, across from Cook Park on the corner of Mexico and Oneida. Today we noticed a number of large and unusual growths on a purple Mountain Ash in our front yard These growths only seem to be growing on the south side of the tree and only on the lower branches (photo attached). Is this a disease? Seeds? or something else? Should we remove them? Spray them? Leave them alone?
We will appreciate your answer.
The Grounds family
Denver County Colorado
Expert Response
Thank you for the excellent picture you sent with your question. I believe these green clusters hanging from the branches on your tree are ash flower galls. They do not harm the tree and are considered a ‘cosmetic’ nuisance. These galls are caused by the tiny eriophyid mite. To learn more about insect & mite galls that affect trees, feel free to explore this free Fact sheet based upon research out of Colorado State University: https://extension.colostate.edu/topic-areas/insects/insect-and-mite-galls-5-577/
There is a myriad of free online publications out of CSU on a variety of gardening topics (insects, yard & garden questions about diseases, flowers, shrubs, trees, grasses, etc.) you can find a complete list at https://extension.colostate.edu/publications-2/
