Trees ornament our lawns, provide shade, block wind and provide refuge for scores of birds and other critters. Healthy, growing trees, however, also have healthy, growing roots. Vigorous roots can eventually threaten or invade underground utilities, foundations and the roots of other trees and vegetation. Prevent roots from taking over by trimming them. Careful trimming includes shortening roots in a way that does not compromise the health of the tree. After trimming, take measures to keep the roots from extending back into unwanted areas.
Water the ground around the tree thoroughly to dampen and soften the soil. Leave the water to seep into the soil, then wait until the soil dries to the point of still being damp but not soggy.
Loosen the top layer of soil, overturning it with a hand trowel. Feel out the roots and take care to not stab them repeatedly with the trowel blade.
Remove soil by hand, placing it temporarily in a wheelbarrow or on a tarp. Scoop out soil from along the sides and underneath the roots, using the trowel only when necessary to break up compacted soil.
Cut the ends of roots that need to be trimmed. Make clean cuts through the roots, sawing through them with a root saw. From the trunk, trim roots no closer than the distance of three times the trunk's diameter. Do not trim roots beyond points where the diameter reaches the size of a fist or larger. Do not remove more than approximately one-third of the total roots and no more than one-quarter from one side.
Dig a trench in front of the pruned roots. Embed a strong root barrier made of plastic, metal or concrete into the trench. For more vigorous roots, use a root barrier that measures at least 12 inches high and 10 feet long.
Replace the previously excavated soil, covering the roots and the root barrier. For unhealthy soil, blend in compost and peat. Wait at least 6 weeks to add fertilizer. Compact the soil and ground level, then water the ground thoroughly.