Cypresses (Cupressus spp.) are evergreen trees that adapt well to various climatic conditions. The coniferous trees are widely used as screens, hedges or specimen plantings in landscapes. Cypress trees grow well in areas of full to partial shade and established trees are low maintenance. Cypresses are not among the trees that cause foundation damage.
Conifers such as cypress have finer and more fibrous roots than a lot of other trees. These roots do not mine the soil for water as compared to trees like oaks and poplars. In case there is evidence of foundation damage from a large tree planted near the house, it is best to remove that tree and plant a cypress tree in the area, according to "The Complete Idiot's Guide to Trees and Shrubs." Other suggested trees that do not cause foundation damage include pine, dawn redwood, ginkgo or chinaberry.
The roots of cypress trees are more tolerant of wet soils as compared to a large number of other tree species. However, oxygen for root and tree growth is just as important as for other trees. Therefore, under times of submersion, tree growth is relatively slower. Cypress roots do not grow very deep into the ground, hence less damage to foundations. Despite the shallow roots, the tree is well tolerant of windstorms and heavy winds.
Cypress trees that are growing in very wet or poorly drained soil produce their distinctive, protruding roots called knees. These knees are often also seen on trees that are planted in well-drained soil but in less quantity. Though the common assumption is that the knees allow the roots to absorb the required oxygen from the air, this theory is yet unproven, according to "Gardening in the Humid South."
Taking Care of Knees
Cypress trees grow best in fertile, deep and well-drained soil and benefit from occasional rainfall. The tree has a rapid growth rate for during the first 10 to 15 years of growth. All mature cypress trees will eventually start to produce knees unless they are planted in very sandy soil. The presence of knees creates no other significant problems except making mowing around the tree a hard task. The best way to take care of this problem is to use a sharp hatchet to chop off the roots that are growing these knees.