ROOT SPREAD and ROOT IDENTIFICATION
How far from tree will lateral roots spread? Found a field tile blocked by tree roots. Nearest likely culprit is a black walnut. Next most likely a very large mulberry. The root blockage is well beyond the branch spread of either tree. Is there a big difference in the appearance of black walnut and mulberry roots? THANKS!
Knox County Illinois
The roots of trees of all species will extend far beyond the edges of the branches (also known as the drip line). As a rule of thumb, arborists state that tree roots will extend outward AT LEAST as far from the tree as its height. Depending on species and soil type, they may extend as much as twice as far as the height.
For example, a tree that is 50 feet tall will have roots extending outwards 50 feet in each direction.
After clearing your lines, you may want to consider installing an underground barrier the length of your septic field, to prevent tree roots from entering the lines again. This is described briefly on page 5 of this publication from Clemson University: http://www.clemson.edu/extension/hgic/plants/pdf/hgic1726.pdf .
One of the products used for creating these barriers is Typar Biobarrier: http://www.typargeosynthetics.com/market-sector/landscaping/
Please let me know if you have any other questions.