Building a Retaining Wall Near Trees? Or Planting Near a Wall?

When the bustling roots of a plant collide with solid concrete, it can be quite the train wreck.

Without careful planning, planting a tree near a retaining wall, or adding one near a mature tree, can spell trouble for both.

That’s why Chin from California wanted to make sure she got it right. She reached out to ask how to level out her yard before building and keep her Aleppo pine unscathed in the process.

The two can live in harmony. Here’s everything you need to know about making the relationship work.

What to Do About Retaining Walls Near Trees or Tree Roots

Both building and planting take lots of time and energy. Before you start, make sure you get the best outcome by reading this.

Can I build a retaining wall over tree roots or around existing trees?

While you can’t lay concrete or set stones on established roots, you can surround your plant with a carefully planned enclosure.

Should I cut the tree roots before building?

Ideally, it's best if you don't. When you start trimming, you can deprive the plant of vital water and nutrients. You can also affect the tree’s stability, increasing the likelihood of failure. Plus, there’s no way to guarantee that the loss of roots won’t damage or even kill the tree later.

If you can, build the wall past the farthest spread roots. Of course, that’s not always an option, especially since they can grow 10, 15 or even 20-plus feet beyond the trunk.

Before attempting to prune roots, read this to learn what you should and shouldn’t cut. You should never make cuts near the trunk or in the drip line, the area under the canopy.

Bear in mind that cutting roots is challenging and risky, so if you’re not 100% confident about what to remove, call an ISA certified arborist®. Most reputable companies, like Davey, over free consultations.

Can tree roots do damage to retaining walls?

It may seem like they are no match for durable stone or concrete, but woody roots can do real damage.

Much of a tree’s growth happens underground and out of sight. The below-ground roots that we don’t see can sneak under the structure to crack or upheave it if it’s too close.

Can I plant trees near retaining walls?

It's best when the two are as far away from each other as possible.

If you want to plant a new tree, find a spot that’s as far away from the wall as the plant will be once it’s fully grown. So, if your new tree will reach 15 feet tall, choose a planting spot at least 15 feet away.

What are the best trees or plants for the top of retaining walls? 

Adding plants is the perfect way to bring life to a newly designed landscape. Perennials and shrubs are usually the best choices to plant close to retaining walls.

If you’re set on adding a tree for a bigger burst of green, choose a small tree, like one of the ones below. And plant those near, not on top of, the wall.  

Check out this list of small trees to find the right one for you!