Surface Roots

May 6, 2012 lawanda Newspaper Columns

Just as a tree attains the majesty for which it is destined, its roots may begin to rise up from beneath the soil. These surface roots are difficult to mow and trim around and may cause a tripping hazard.
While some tree species are more likely than others to form surface roots, the reason they appear is simply that the roots are looking for optimum growing conditions: oxygen, water and fertility. If the best option is near the soil surface, then that’s where the roots will grow.
When soil around the tree is compacted, there isn’t sufficient oxygen between soil particles, so the roots look upward to where our atmosphere holds plentiful oxygen. Both too much and too little water may cause roots to surface. A high water table that saturates the soil fills the space between soil particles with water instead of oxygen, making the area inhospitable to the roots. Alternatively, roots may grow upward when a homeowner regularly gives the lawn surrounding the tree a shallow watering because there isn’t sufficient water deeper down.
Another oxygen stealer is competing plants growing near the tree – either grass or other ground covers.
You’d think that adding compost to the area around a tree would be a good thing – and normally it would, unless the lawn is watered too often. This causes oxygen-demanding soil microbes to proliferate and deplete oxygen, which isn’t easily replenished because of the water continuously filling the spaces between soil particles. So again, there is not enough oxygen for the tree roots and they look skyward.
Almost seems like you can’t win, doesn’t it?
The solution is to mulch around the tree with 3-4 inches of a coarse organic material that will allow water to penetrate. Too fine of a material will mat together and form an impervious layer. Wood chips or shredded bark is best. The mulch should not touch the tree trunk. It should be shaped like a donut rather than a volcano. Spreading mulch out to the dripline of the branches or even further is recommended.
Surprisingly, the solution for trees already already showing surface roots is the same as the prevention: a coarse mulch a few inches deep, spread to the dripline.
Now, some “Do Nots.” Do not cut surface roots, as injury to the roots will invite decay, pests and diseases and cause a decline in the tree’s health, possibly even lead to its death. Nicking by a mower blade or weed eater leads to the same issues. Do not place a weed barrier under the mulch because it will inhibit water penetration and encourage the mulch to mat together. Do not use rocks or stones, as the weight of them will compact the soil. Do not mound soil over the roots to make a raised bed planter. The weight of the additional soil will compact the soil below and cause the roots to be starved for oxygen.

Gardening techniques and toolslandscapingTrees and Shrubs


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