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Tuesday - March 19, 2013

From: Austin, TX
Region: Southwest
Topic: Erosion Control, Shade Tolerant
Title: How to stabilize a slope under Red Oaks?
Answered by: Joe Marcus

QUESTION:

A portion our front "yard" (20x40 feet) is a limestone hillside shaded by 3 large spanish oaks. The small amount of grass holding onto the hillside is now gone from the drought, and the hill has eroded down to rock and roots. My questions are: 1. How to stabilize the slope without damaging the tree roots; eg, if terrace, how deep can topsoil be added; use of rock versus soil/mulch; mesh or other means to keep the soil in place. 2. Once the hillside is stablilized, what drought resistant grass or plants can tolerate full shade and require little maintenance. Thank you for any help!

ANSWER:

With more than 8000 questions and answers (as of March 20, 2013) published in Ask Mr. Smarty Plants, many questions have been answered already. A particularly good answer to a recent question covers most of your issues regarding shade-tolerant ground-covers.

Terracing is an effective way to reintroduce soil to an eroded slope. The amount of soil you can add will depend on what you wish to keep growing there. In general, you should add no more than one inch of soil around the trunk of trees or shrubs. However away from the trunk and especially down hill from a tree, the soil can be deeper. Terraces on steep slopes usually require construction of retaining walls using rocks, masonry or timbers.