Each tree species has some unique rooting characteristics but in general, 90% of a trees roots are located in the top 2 feet of the soil. The other 10% of the root system can go much deeper, 12 feet or more. Tree roots need oxygen to provide nourishment to the tree. Most of the oxygen is located in the top 2 feet of the soil, so that is where the majority of the roots can be found.

The spread of the root system in the top 2 feet of the soil can be as far as twice the distance of the tree canopy. As an example, if the tree canopy is 30 feet wide, the trees roots could extend at least another 15 feet from the tree canopy drip line. As a general rule, the farther away the tree roots are from the tree, the smaller the roots are in circumference.

Tree roots compete with other plants roots for water and fertility. Heavily watered grass encourages more surface rooting. The roots go for the easiest and most available water source. Deep rooting depends on the species, the soil, and the availability of moisture. Very heavy and hard clay discourages deep root growth. Sandy or loamy soil allows for deeper root penetration. Oak trees would be an example of a deeper rooted species and Maple trees trees would be an example of shallower rooted species.