Question:
How much space does a tree's root system need to grow properly?Answer:
The majority of roots, especially those roots that are responsible for water and nutrient uptake, are in the upper 6 to 18 inches of soil. Structural roots that radiate out from the tree and provide support and anchorage can reach a distance of more than four times the dripline of the tree.
Where space is limited (such as in the right-of-way; i.e., the space between the sidewalk and curb), the minimum size of the tree rooting area depends on the mature size of the tree.
- For small trees (less than 30 feet tall), the total planting area should be at least 50-150 square feet with two or more feet between the trunk and any pavement or structure.
- For medium trees (less than 50 feet tall), the total planting area should be at least 150-300 square feet with four or more feet between the trunk and any pavement or structure.
- For large trees (more than 50 feet tall), the total planting area should be at least more than 300 square feet with six or more feet between the trunk and any pavement or structure.
These guidelines apply when soil depths are at least 3 feet. If the soils are shallower, plant small-statured trees. If soils are poorly drained and/or compacted, provide more planting area.
Remember, these guidelines represent the minimum planting area. All trees will be healthier and grow more successfully when given more rooting area.