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The Root System of Oak Trees

oak image by Marek Kosmal from

The majestic oak trees belong to the Quercus genus and are supported by well-adapted sustainable root systems. There are hundreds of oak species around the world that thrive in dry soils, in wetlands, along banks and in a variety of soil types. Once the acorns fall in the autumn season, the rooting systems of new oak trees begin to develop and when left undisturbed, oak trees can live for more than 1,000 years.

Acorn Germination

After falling from the tree, the acorn begins to rapidly germinate if the temperature remains above 50 degrees Fahrenheit. The roots grow into the ground until the temperature drops and then its growth slows down or stops until the spring. In the first year, these new oak seedlings will have a taproot that is 1 foot long and 1/2 inch thick, and the first years of the tree's development will be focused on establishing the root system of the oak tree.

Soil Conditions

New oak seedlings take root well in loose, well-drained soil that receives partial to full sunlight. Oak trees need calcium, magnesium, nitrogen, phosphorus, potassium and sulfur from the soil. The taproot extends deeper into the soil and moisture easily penetrates the soil. Use a layer of mulch to keep the soil aerated for a healthy root system.

Large Roots

Oak trees develop very deep rooting systems that branch off of its main taproot. Over time, the taproot's prominence recedes and is replaced by numerous large lateral roots that form the lateral root system. These lateral roots penetrate the soil 4 feet deep and extend laterally to 90 feet. This is the main part of the root system that supports the tree.

Fine Roots

From these large lateral roots develop the fine root system, which extends out into the soil, forming a dense root mass that grows within the three-foot depth under the soil's surface. The fine roots are responsible for absorbing nutrients and moisture from the soil.


Do not disturb the soil around oak trees to keep them healthy and strong. Limit traffic around the oak trees, and do not perform extensive landscaping under or around existing oak trees. Oak trees generally do not require special irrigation since its rooting system takes in adequate moisture from the soil. Avoid watering established trees during the warm period from spring through the beginning of fall, and only water away from the base of the tree in the beginning of spring if the winter months experienced very little rainfall or moisture.

Root Diseases

Weak oak trees are susceptible to fungal infections. The Northeastern Area State and Private Forestry states that Armillaria mellea, Armillaria tabescens and Inonotus dryadeus are three fungi that cause root rot in white oak trees and other oak trees. The Florida Department of Agriculture and Consumer Services states that Ganoderma and Phytophthora also cause root disease in weakened oak trees.

Oak trees compromised through root disturbances or climactic extremes, such as drought or flooding, are susceptible to these fungi that feed off of the roots and then invade the rest of the tree. Over time, the disease cuts off the tree's water and nutrients causing it to eventually die.

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