How Deep Do Oak Tree Roots Go?

The majority of oak tree roots grow in the top 18 inches (45 cm) of soil. These roots spread laterally from the tree, 3–7 times wider than the spread of the branches. The deepest root of the oak tree is the taproot, which typically grows straight down beneath the trunk to a depth of 3–5 feet (1–1.5 meters).

  • Lateral oak roots mostly grow at a depth of 18 inches.
  • Lateral roots grow 3–7 times the circumference of the oak’s branches.
  • An oak taproot grows to a depth of 3–5 feet.

Instead of picturing an oak’s roots as a mirror of the aboveground branches, picture a network of shallow roots that spread far and wide to gather nutrients and keep the tree anchored in place.

How deep do oak tree roots grow?

Do Oak Tree Roots Grow Down or Out?

Oak tree roots spread outward more than downward. The majority of the roots that support your oak tree are within the top 18 inches of the soil. The only oak root that grows downward is the taproot, which grows straight down into the soil, typically to a depth of 3–5 feet.

  • Oak roots grow mostly outward, not downward.
  • Only the taproot, which is just below the trunk, grows downward.
  • The roots of a mature oak can spread outward 75–250 feet (20–75 meters).
  • The furthest spreading roots are extremely thin, hairlike fibers.

Although oak tree roots can spread out more than 200 feet, the roots taper drastically as they get farther from the tree. Most of these far roots are extremely thin fibers, more like thread or hair than large roots.

Are Oak Tree Roots Invasive?

Oak tree roots can be invasive and damaging to structures, paved surfaces, and pools if the tree is growing within 20 feet of the structure. Keep the following in mind:

  • Oak trees should be at least 20 feet (6 meters) from houses, paved surfaces, pools, underground water lines, sewer lines, septic tanks, and other structures. 30 feet (9 meters) is safer.
  • Roots can invade and clog water lines and septic tanks if the oak is planted too close.
  • Oak roots are capable of buckling pavement, such as sidewalks and driveways, if the paved surface is within 20 feet of the tree.

Keep in mind that oak roots spread even wider than that of other trees. Because the roots are relatively shallow, oaks are among the most likely trees to destroy nearby paved surfaces.

Can Oak Tree Roots Damage Foundations?

As with paved surfaces and underground water lines, oak roots can damage foundations. In order to assess if your oak tree is a threat to your home, consider the following:

  • Oak roots damage foundations within a 20-foot (6-meter) radius of the oak’s trunk.
  • At a distance greater than 20 feet, oak roots are too small to cause serious damage to a foundation.
  • Consider cutting down your tree or consult an arborist if you believe your oak tree poses a threat to your foundation.

Beyond 20 feet from the trunk, oak roots taper off into a network of very fine, threadlike roots. Although they may spread hundreds of feet, these small roots do not pose a threat to your home. If you have an oak tree growing too close to another structure, make a plan to fell the tree yourself or contact a tree removal expert.

Will Cutting Roots Kill an Oak Tree?

It is very dangerous to excavate the ground and cut oak roots within 20 feet of the tree. The roots within the first 20 feet of the trunk are critical supports that keep the tree upright.

  • Do not cut roots within 20 feet of the oak tree. Roots close to the trunk are crucial to support the tree.
  • Cutting roots within 20 feet may cause the tree to fall unexpectedly.
  • Fallen trees may damage homes, other structures, and vehicles. They may also fall into roadways or onto neighboring property.
  • Avoid excavating for patios, sidewalks, driveways, or foundations within 20 feet of your oak tree.

A 30-foot tall oak tree falling on your home can result in serious property damage. To eliminate this risk, think of the 20-foot radius around your oak’s trunk as a protected zone where no digging or root-cutting should take place.

Do Oak Tree Roots Grow Deep Underground?

Oak tree roots are relatively shallow, but make up for it in their lateral spread. While the vast majority of your oak tree’s roots grow no deeper than 18 inches below the surface, they can spread 3–7 times the circumference of the tree’s branches. In comparison, most other trees only have a lateral root spread around 2–3 times the size of their branch spread.

To keep structures, paved areas, and underwater sewer lines safe, plant oak trees at least 20 feet from these structures. Avoid excavating and cutting roots within 20 feet of your oak’s trunk, as this can seriously damage the tree and cause it to fall. Now that you know more about your oak, you can safely take care of it, or determine if the oak in your yard needs to be removed.

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