Ask Burton: This week, we’re looking at soil, and how you should treat your trees versus the rest of the landscape. Q: I have a new flowerbed that I want to thrive on the west side of my home, and I also want to plant a tree nearby to eventually provide shade in the afternoon. How should I prepare the soil for these?

A: If there’s one thing that unites almost all our Metroplex area gardeners, it’s a near universal dislike of the black clay that most of us have to deal with. Here are a few good recommendations to improve your own success, and the answers are NOT the same:

Beds: Add significant amounts (2-3″ layers) of expanded shale and finished compost to the proposed bed area, and till it as deeply through the soil as possible. Finish your plantings with a thick layer (at least 2″ deep) of your favorite shredded wood or bark mulch. Your plants will love the compost-rich soil and the permanent drainage caused by the shale, and you’re realistically able to amend enough soil for the long term needs of the shrubs and flowers you’re planting.

Trees: The thorough soil preparation you should lavish on your flowerbeds is NOT what we recommend for trees! While the top dress mulching remains the same, you should not add nearly as much organic material to the back fill soil around your shade trees. A normal soil contains a small amount of organic material; plants love more than this, but if you make the soil too rich with organic material around the root back fill of your trees, tree roots will go back into the enriched soil and circle the planting holes instead of rooting out as they should. A healthy, established shade tree’s roots should extend anywhere up to twice as far from the trunk as the canopy edge of the tree, and this is an impractical amount of soil to change out.

Our local soil doesn’t have much organic material in it, and even less by the time a lot has been graded and compressed by massive machines, so I do add some compost and expanded shale to the back fill to give your tree an easier start. Don’t overdo it! The majority of the soil you put back into the hole should be broken native soil, and plant the tree slightly higher than grade with an exposed root flare. Plant a healthy tree that’s well adapted to our area, and you’re unlikely to have many problems.

This is a great time to plant here in North Texas, and we have all of the soil amendments you need.

Burton specializes in diagnosing and solving plant problems. If you have a question for Burton, please email him at and include photos showing the problem.