Healthy roots allow plants to thrive. Roots support plants, conveying water, nutrients and oxygen. When roots interfere with lawns, grow into pipes and push up foundations and driveways, they become problems. Root damage is estimated to cost more than $100 million per year in the U.S. in maintenance and liability costs.
Roots don’t “seek” water. They grow where water, nutrients and oxygen are available. Irrigating your lawn takes care of the water needs of your grass, but may also supply nearby trees and shrubs with extra water when their roots grow into your damp yard. Fast-growing trees with invasive roots, such as poplars, willows, elms and locusts, may provide quick shade, but shouldn’t be planted in urban landscapes.
Once roots invade a yard, it is hard to control them. Roots grow larger with age and exert more pressure on resisting surfaces. Sawing off wayward tree roots seems like a possible solution, but this may create a hazardous and costly situation if the cut roots destabilize the tree, allowing it to fall. In most cases killing roots will damage or even kill a tree. Tree removal is the best solution, but rarely do people want to cut down their trees.
Underground physical barriers are an alternative solution. Root barriers inhibit root growth into irrigation systems, walkways, landscaped areas and driveways. Some fabric products control roots with a metered release of root-inhibiting herbicide that doesn’t damage the rest of the tree. Others are simply root deflectors with no chemical controls included. Installation involves digging a trench parallel to and around the structure to be protected (not the tree), lining the trench with a continuous piece of the product and filling it in.
There are issues with root barriers. They don’t last forever (15 years or so); can be costly; may cause roots to bunch up outside the barrier in large masses, creating other challenges; and may cause roots to grow around the tree, strangling it. Some products are water-permeable and others are impermeable. Impermeable products may result in waterlogged soils that drown plants. Digging the trench to install the product may damage trees. The closer you get to a trunk with the barrier, the higher the risk of damaging or destabilizing the tree.
In an ideal world, only trees with non-invasive roots would be planted in the first place, and people would water deeply to encourage deeper roots for healthy trees.