QuestionI have cypress knees under my house and wondering the best way to get rid of them before they get too tall to cause damage to my sub-flooring. Thanks for your help.
AnswerIF you want to keep the cypress, about all that can be done is just cut them off at ground level. It will not damage the tree this way. If you want to get rid of the cypress trees then apply a herbicide called Roundup to the fresh cut knee and the roots will transport the herbicide to the tree and other roots and kill the tree. I would get an old paint brush and paint the stump with the Roundup straight from the container. Throw the brush away after you finish.
The knees will more than likely grow back in another location but as they do you can cut them off. They do not really grow that fast so once every couple of years you can inspect for new ones and handle them then.
The "cypress knees" usually only develop when grown in or near water for most of the year. In wet soil conditions, the bald cypress will form sections of root growing above ground to gather oxygen. The size of cypress knees on an individual tree is directly related to water level. They can grow as tall as 36 inches depending on the wetness of the soil but normally are about 5-12 inches tall. The function of cypress knees is some what mysterious. They were thought to aid the roots in gas exchange under flooded conditions but removal of the knees seems to have no ill effect on the tree.
About all that can be done is cut the knees at ground level. This will not harm the tree but will need to be done again as new ones grow later.
