One thing thatís really fun about my job is learning new stuff all the time. Sometimes itís not good stuff. I have been stunned to discover what a huge number of trees have been planted too low. There seems to be several reasons why this problem exists.
Many trees have simply been set too low in the planting operation. Holes were too deeply dug. Other trees were planted at about the right level, but settled due to the wrong backfill or weak rootballs.
One of the most common causes of deep tree planting problems starts at the growing operations and sometimes in the nurseries. As trees grow, they are stepped up from seedlings to 1 gallon pots and then to increasingly larger containers. Often during this process more and more soil is added to the top of the root ball. Why, I donít know. By the time the tree is ready to plant, it may be several inches deep in the container.
That fact combined with the planting mistakes often puts the true top of the root ball several inches underground. This covering of the tree ball with soil can also happen on field grown trees by the cultivating plows. Trees that are planted too low have several problems. Soil above the root ball shuts off oxygen to the feeder roots and carbon dioxide canít escape from the soil. Roots that do grow often circle and grow primarily in the soft, loose textured, added soil. The coiling roots can girdle trees several years after planting. Then also there is a girdling action from the soil moisture on the bark of the tree.
A frustrating part of the problem is that the damage doesnít start to show up until sometimes 10-15 years after planting when the tree is trying to mature and offer its beauty and shade. These symptoms can also show up the first few years. Watch for poor top growth, light colored foliage and a thinning canopy.
Itís easy to tell if a tree has been planted too low. The trunk will go straight into the ground like telephone pole instead of having a distinctive root flair at the soil surface. The solution is relatively easy too. Remove the excess soil down to the true top of the original root ball.
This work can be done by homeowners with a hard rake or by professional arborists with a special tool called an air spade. It is basically a sand blaster with a customized nozzle that blows the soil away from roots without injuring them.
Girdling roots can be pruned away if needed at this time. If the excavation down to the top of the ball is not too deep, the area can be left concaved and lightly mulched with shredded tree trimmings. If the soil removal leaves a deep hole, a grate may have to be added that can serve as a structure for ground cover.
The long-term solution to this problem is to plant your trees properly, leaving the actual root ball 2 inches higher than grade and backfill with native soil only. With this technique not even settling will leave the tree too deep in the ground.
Root Flare Management
Question: In January, we hired landscape professionals to plant two live oaks. The workers did not cut the wire or burlap from around the root ball. They told us not to water for three weeks. When we did water to add root stimulator, the trees immediately began to die. Last week, the workers came back and planted two replacement trees. These live oaks are about 12 feet tall, and again the workers did not cut the wire or turn back the burlap.
This time, they told us to water immediately until water stood in the watering ring around the tree, and then to cover the area with mulch to retain moisture. They said to keep the mulch about 3 inches from the tree trunks and to water on Sundays and Wednesdays. One of the trees has turned nearly all brown and lost 75 percent of its leaves. The other tree has a few brown areas in the leaves. Should the wire and burlap on the ball of the tree be removed? D.C., Dallas
Answer: The burlap should be removed. There will usually be some excess soil under the burlap on top of the root ball. That soil also should be removed. The only root stimulator I recommend is my recipe for Garrett Juice (see Resources to request handouts).
I don't recommend water rings. If trees are planted using natural techniques, if the planting hole is backfilled with soil that was dug out to create the hole, and if the tree is watered thoroughly at planting time, additional water other than that used on surrounding plants is rarely needed. Deep watering twice a week is almost always too much. Many more trees die from too much rather than too little water.