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Dealing with Above-Ground Tree Roots


Q. I have a Bradford pear tree. It's about 25 years old, roots are showing themselves above ground about three feet from the trunk and they're getting larger. What causes this and is it possible to tear them out without harming the tree? Maybe it wasn't planted deep enough to begin with? Thanks,
    ---Ray in Oklahoma City, OK
A. Many types of trees develop surface roots naturally, and "tearing out" those roots would likely kill the tree. Planting depth is not the problem; in fact, deep planting stresses trees by burying part of the trunk below ground, where it is subject to bark-killing rot. You should always plant a tree high enough in the ground that the root flare is showing; that's how Nature does it, after all—just look in the woods. Bury it deep and you could well have a really expensive problem to deal with a few years down the line.

Q. We have many trees whose roots have spread over the surface of the yard. The grass in those areas has died out and we would like to get it back. The local lawn service told us we would have to remove the trees to get grass to grow in those places. We do not consider that an option. Can we cut off the roots that have come to the surface and replant the grass without killing the trees?
    ---Dick and Phyllis in Hockessin, Delaware
A. As detailed in a previous Question of the Week we devoted to growing grass under trees, the problems in this coexistence are complex. First, there are only a few varieties of grass that can survive the dense shade of a tree canopy—fine fescue comes to mind for your region of the country—and these grasses can't take much, if any foot traffic. They are also clumping grasses that need to be reseeded or overseeded in the fall, sometimes yearly, to keep them full.

But many experts feel that the intense competition for food and moisture is even more of a limiting factor than shade. Big trees have big, efficient roots that tend to take all the water in the area for themselves; and feeding a lawn overtop of those roots is perhaps the perfect way to deliver most of the food to the trees instead of the lawn.

In short, lawns under trees are always going to be problematic at best, and require much more care than lawns in sun (or even shady lawns that don't have trees giving them wedgies and stealing their lunch money). That's why the areas under trees in Nature tend to be bare, covered by roots or dotted with tough and scrappy little plants.

But if deterred by my warnings you are not, have the area covered in one to two inches of high-quality yard-waste compost or a mix of compost and screened high-quality topsoil. Then seed fine fescue as close to August 15th as possible (to give the new grass time to establish before the fall leaves drop). Don't try and sow cool-season lawn seed in Spring or Summer; and make sure any topsoil you buy is dark in color when it's dry.

Unlike whacking away at them, covering the roots with some soil won't harm the trees a bit. And if you're willing to give the grass extra food and water, stay off of it as much as possible and overseed every fall, it could work nicely.

But it would be much less work to cover the roots with a mix of topsoil and peat moss (for acidity) and then establish a colony of mosses under the trees. High-quality mosses are available in the form of sod, plugs and spreadable powders, can be started in the Spring, never need cutting or feeding (just supplemental water and maybe a little help staying acidic), are green all year round and are a perfectly natural ground cover under trees. Speaking of 'ground cover', many low-growing, low-care ground covers would be just as good under trees as true moss, with the added advantage of being able to take more foot traffic than moss.

Q. A large, healthy, shade-providing tulip poplar is lifting the sidewalk in front of my home. The sidewalk has broken at the seam and one of the 'blocks' has been raised a couple of inches. Can I remedy the situation without harming the root (and the tree)? Am I doomed to making repeated repairs to the sidewalk? Can I trick the root into going in another direction?Thanks for any help; this tree deserves to be saved.
    ---Robert in Havertown, PA.
A. First, a warning: Tulip poplars are fast-growing but relatively short-lived trees. Towards the end of their life, they tend to become brittle and have a nasty habit of dropping large and potentially deadly limbs down upon the unsuspecting human head. So when yours begins displaying this bad habit, plan to have it removed quickly. Until that time, however, you may indeed continue to enjoy its ample shade.

Now, the easiest answer is to remove the affected portions of the walkway permanently and reconstruct the area to accommodate a bigger 'planter effect' at the base of the tree; perhaps using a nice wrought iron something (like a fancy fence or a classy gate) as an accent—and a visual reminder that there ain't no sidewalk in that spot anymore.

And I happen to know for a fact (I did it successfully 20 years ago) that you can have an experienced arborist sever a wayward root or two on these monsters without any ill effect. So if it is just one big bad root causing the majority of the problems, a small root-ectomy may also be in order.

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