Nearly fifty percent of urban trees die before maturity. Many container-grown trees are doomed before they are planted, while others die during adolescence.
Why?
Trees grown in a typical container nursery system can develop traits and characteristics that hinder their post-planting development. These traits are exacerbated by production techniques that focus on optimal growth. Some of these traits turn negative and lead to lesser-quality trees. Sometimes the reduction in quality is structural, other times it’s in health. Sometimes both. Some of these traits develop in the nursery, while others manifest over time from incorrect planting techniques.
Poorly planted trees start to show signs of stress and strain between one and twelve years depending on the number and severity of issues. Here is a short list of negative tree traits and characteristics to look for when selecting a tree from a container-grown nursery.
Girdling Roots
Nursery containers cause roots to circle inside. Left unchecked, root(s) can circle around part or all of the trunk/root area. Girdling roots cause a host of instability and health issues including dead branches, partial root or trunk death. Extreme girdling can cause trees to snap out of the ground from lack of structural integrity. (see photo of pistache tree “popped” out of the ground). Girdling roots can be pruned when very young but there is always a risk of disease, temporary stunting, root suckers, and death.
Root Suckers
Root suckers can happen on most trees. Sprouts and suckers growing from the roots or on the lower trunk usually indicate some form of injury or over-fertilization with nitrogen. Some tree species are naturally prone to suckering, especially fast-growing types. Most trees will continue to sucker or sprout for the rest of their lives. This leads to constant pruning and increases maintenance costs. Some of the issues causing root or lower trunk sprouts include over-fertilization, disease, insects, (especially borers), mechanical damage including topping and over-pruning.
Sap Flow
Be wary of trees with sap flowing from the trunk or branches. It usually is a sign of insect damage, disease invasion, or recent mechanical injury. Sometimes it’s a natural phenomenon.
Bad Grafting
Many tree species are grafted. Grafting combines valuable traits onto one tree. However, some grafts are only partial unions. Look for included bark lines, partially dead scion or rootstock. Sometimes there is a size disparity between the scion and rootstock that indicates a graft union issue.
Double or Multi-Leaders
Unfortunately, most trees are topped in the nursery. Topping the main leader changes the apical dominance which can lead to root and trunk sprouts. Left unattended a topped nursery tree usually forms two to four new leaders growing near the topped area. As they grow larger (after 8-12 years) they become structurally weak, and one or more limbs fail. (See photo of spit limb.) Removing one or more of the multi-leaders may be necessary for long-term success.
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Tree Planting
Most urban trees are planted too deep.
Planting trees correctly is the difference between success and death. This can’t be overstated. The most important factor when planting a tree is positioning the root crown two inches above grade after settling. To achieve this, first, water your tree before starting the planting process, then dig the planting hole about two inches less than the rootball is deep or about twelve inches for a standard 15-gallon container. Dig the planting hole at least three feet in diameter (wide). After digging the planting hole, lay a two-inch diameter tree stake across the planting hole making sure it is resting on the original grade. Measure the distance from the bottom of the hole to the top of the stake. This measurement should be about two inches less than the depth of the
rootball. Some adjustments may be needed, especially if the rootball falls apart. Fill the planting hole halfway with water before taking the tree out of the container. Quickly and efficiently take the tree out of the container and loosen the circling roots on the sides and bottom.
Planting the tree is easier with two people. One person sets the rootball into the planting hole, holding it upright while the other person insures it is two inches above grade. I find it easier to use a level and tape measure. With the bubble set at level, measure the distance from the original grade to the bottom of the level. This should be two inches. If not add or remove soil from the planting hole.
Backfill the planting hole after setting the tree at the proper height. Add soil amendments if you like but it usually is not necessary. I like to install three stakes and six or more flexible ties to support the trunk. After two or three years the tree should be able to stand upright on its own. If it can, remove the ties and stakes. Tree stakes are temporary.
I do not like berms. I coil in-line drip tubing around the rootball area and beyond. Hold the tubing in place with drip staples. Make sure to add a filter and regulator on the in-line drip tubing at the valve. Add more in-line tubing in circles around the tree as the root system spreads. Add two inches of mulch or bark around the tree past the last in-line drip tubing two feet. Feather the material thinner as it gets near the trunk. Water the planting site again. Check the irrigation system to ensure it’s putting out an even amount of water. Clean up.
Do not fertilize the tree at planting, especially with nitrogen. The tree has plenty of fertilizer in the rootball. Wait until the tree can stand up without support (no stakes) before it is fertilized. Most people think at this point they are done. However, it is quite the opposite. Your work has just started. Check on the tree daily for proper amount of moister in the rootball. It will be several months to a year before the tree is established. During this time, it is critical to monitor the tree and make minor adjustments as needed.
I tell new tree owners,
Don’t Just Plant and Walk Away…