Black Acacia Tree Root Problems

Root Extent

• Black acacia puts out primarily shallow roots in all directions that extend from one to 1 1/2 times the height of the tree. In their native range, some trees put out roots extending as far as 165 feet. Some specimens, however, have been documented with deep roots as well, mostly in the Southwest and Plains states, where it is assumed they have to grow deeper to find water.

Sprouts from the Roots

• Suckers can and do sprout into new trees from anywhere along the roots as well as from stumps; this characteristic earns the tree a classification as an invasive or nuisance plant in many states, but also acts as a survival behavior: Black acacia is often found growing in disturbed sites such as mined areas. Sprouting from seeds is not common as they are very hard, so the natural germination rate is low.

Control of Invasive Stands

• Control of invasive or problem black acacia trees is possible by removing suckers and mowing sprouts repeatedly over several years. The locust borer is a common pest of the tree, but there is no research on whether it damages the trees enough to reduce their population significantly. Deer graze on the sprouts and young trees, but not enough to decimate a stand. Other animals that feed on the tree include rabbits, grouse and squirrels. Black locust is poisonous to humans, though tea may be made from the flowers.

Effects of Fire

• Fire will kill the main stems, but will not prevent new sprouts from growing from the roots. In fact, one study, reported at a 1980 conference on hardwood forests documented by the U.S. Department of Agriculture, reported that fire actually encourages the tree roots to sprout. Combined control methods of mowing and burning seem to result in the most success.