Making a Retaining Wall for a Tree

Last updated on December 2nd, 2011

HERE AT A GARDEN FOR THE HOUSE, there’s no shortage of landscaping challenges. Take the north end of the Rose Garden, where a glorious old maple tree grows on a steep slope. I couldn’t get grass to grow at the tree’s shallow roots, yet weeds flourished there. The cure? A retaining wall, built half-way round the tree:

The wall, built by a professional, and composed exclusively from stones I found while digging in the Woodland Garden, provides not only architectural interest, but a level bed for planting, too. If you have need for a similar wall, perhaps the following pictures will serve as a tutorial of sorts.

To start this project, I indicated with spray-paint the curve of the wall. Then the contractor proceeded to dig a 5-inch-deep trench along my outline, skipping over any exposed roots.

Into the trench went the largest stones. Layering continued until the top of the wall reached the base of the tree.

Because good drainage is essential to any kind of soil retainment, pea gravel was poured directly behind the wall, to a depth of 6 inches.

Now, you might wonder if covering the roots this way will hurt a tree. It won’t. The layer of gravel and the well-draining compost permit roots to breathe. Furthermore, roots are not injured during construction.

If you have a tree that grows on a hillside, and wish to make a garden beneath its leafy canopy, do consider building a demi-lune wall at the tree’s base. It’s the only way to make “under-planting” a real possibility.

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