Specialized root structures of bald cypress that grow vertically above water or moist soil. It is thought that these structures aid the oxygen/carbon dioxide exchange in the roots.
| Bald Cypress - knees
Montezuma Cypress - no knees
Q: I have bald cypress trees in my yard. The root nodules are becoming a problem with my lawn mower. Would it damage the trees if I trimmed them off at ground level? B.D., Dallas.
A: Yes, the knees are part of the root system. Change the area to mulch or ground cover and try to dry out the soil. The knees grow in overly moist soil.
QUESTION: I have a bald cypress, and the roots are coming out of the ground all around the yard. Some are close to the tree and some are far away. The roots come out of the ground for about 12 inches or less and then go back into the ground. How can I keep this from happening? Can I cut the roots that are already protruding without hurting the tree? K.E., Fort Worth
ANSWER: This is a characteristic of bald cypress. Their roots always do this to some degree, especially when the ground stays moist to wet. Improving the drainage and reducing your use of water will help, but the only way to eliminate the protruding roots is to remove the tree. I would suggest instead that you use mulch or plant a groundcover around the tree so you won't need to mow over or around cypress roots.