Pond Cypress Roots and Problems with Foundations

Habitat and Form

• Hardy in U.S. Department of Agriculture (USDA) plant hardiness zones 5b through 9b, the pond cypress is a North American native with little invasive potential and generally is a landscape-friendly tree. Its bright-green foliage is vibrant in spring and summer, and its tall, graceful form may reach 50 to 60 feet over time. Both its rot-resistant trunk and shady foliage suit it to landscape uses, making a low-maintenance statement specimen or street tree.

Knobby Knees

• The pond cypress has growths, called knees, that form from its base, often when its roots become submerged in water. These knees, which are knobby root protrusions, then grow upward and outward, usually breaking free of surrounding moisture. Although biologists have speculated about the purpose of the knees -- to get more oxygen in wet environments, for example -- they aren’t really sure of the knees' function.

Knee Problems

• Fortunately, the knees don’t really seem to form in dry conditions the way they do in wet areas. So unless your house is built on a swamp, growing a pond cypress near foundations shouldn’t be a problem. The tree even does well in a small, confined planting area, such as the kind common in urban areas, and, therefore, makes a suitable specimen tree for a confined space, including along a street and sidewalk.

Bald Cypress Alternative

• Bald cypress (Taxodium distichum variation distichum) is closely related to pond cypress, also is adapted to swampy areas and is winter-hardy in USDA zones 4 through 9. Although bald cypress typically doesn’t form knees unless a lot of water is near, it forms knees more readily than pond cypress. If you are choosing a specimen to plant near a house and are worried about tree knees, then stay away from pond cypress and bald cypress, but pond cypress is a better choice than bald cypress.