Planting trees near your sidewalks adds beauty and can increase your property value. Doing so also provides pedestrians with shade. The downside is that tree roots are a major hazard to sidewalks—roots that grow underneath your sidewalk can push up the slabs, breaking them and making your sidewalk dangerous to walk on.
The usual solution to fix a sidewalk that has been damaged by tree roots is to remove the offending tree root and replace the slab. Unfortunately, the shallow lateral roots that often break sidewalks are a major source of a tree's stability. Removing them can make the tree more likely to topple over during a storm. Worse, removing a tree root is a significant shock to the tree and can cause it to quickly die. It's preferable to stop the problem from ever occurring when you first plant the tree. Here's how.
Choose a Species of Tree That Primarily Grows Tap Roots
Tree species can be broadly defined as having taproots, lateral roots, or both. For example, oak trees typically grow taproots and willow trees typically grow lateral roots. Taproots dive deep into the soil, whereas lateral roots spread outwards from the base of the tree. Since taproots grow deeply before branching out, they present much less of a danger to nearby sidewalks—they're too deep to press up on the concrete slabs. Lateral roots immediately start growing outwards just beneath the soil, so they're more likely to destroy a sidewalk. Choosing a species of tree that only has taproots makes it less likely that your sidewalk will be damaged.
However, choosing a tree species that primarily grows taproots isn't a foolproof method. Compacted soil or dry soil can lead to the formation of lateral roots, even in a species that usually grows taproots. You can help prevent the formation of lateral roots by keeping your tree adequately watered once you plant it, making the tree less likely to grow lateral roots to search for more water.
Install a Root Barrier Between the Tree and Your Sidewalk
Root barriers are plastic sheets that are inserted into the soil and used to direct root growth in plants. They're an excellent way to prevent newly planted trees from damaging your sidewalks. When you plant the tree, insert a root barrier into the soil between your sidewalk and the tree. Angle it towards the tree and make sure it stretches from the surface to at least three feet underground. If roots grow under the barrier, they will be too deep to affect your sidewalk.
Trim Your New Tree Periodically to Keep Growth Directed Upward
Trimming your tree causes root growth to slow, since the tree spends more of its energy regrowing branches rather than expanding its root system. Trimming the crown evenly also helps your tree to grow straight up rather than growing lateral branches, which can help prevent it from encroaching on your sidewalk.
Trees need to be trimmed more often when they are young, and how often you'll need to trim your tree depends on its species and how fast it grows. It's a good idea to call a tree service company after the first year of growth in order to trim the tree's crown and direct its future growth. You'll need to continue trimming your tree as it grows—lateral roots that can damage your sidewalks often appear once a tree matures and begins growing its root system farther out, so your tree may require constant trimming throughout its lifetime in order to keep its growth in check.
By following this advice, you significantly reduce the threat that a newly planted tree poses to your sidewalk. If you need help selecting a species of tree that primarily grows tap roots or need help planting your tree, consult a tree service company like Joshua Tree & Landscape Co. You'll receive advice about which trees suitable to your climate are best to plant near sidewalks.