| For the Times-Union
Sometimes we take trees for granted. We see them as the pillars in our landscape and sometimes forget that they are living things that need the same conditions to live and thrive as our favorite flower, shrub or groundcover.
Often, we think because they are larger and live longer, they do not need as much care, or they are more tolerant of neglect. In some cases, this is true. A leaf disease that would doom our prized rose is barely a minor nuisance to a maple tree.
However, the origin of most landscape tree decline, and eventual death can be traced back to something that was done in the past (sometimes years) by someone not knowing that it would harm the tree. In the horticultural world, these practices that cause tree decline are called cultural causes and most of the time can be avoided.
Let’s explore some of the most common cultural decline causes and how to avoid them.
Giving trees enough space: I recently drove through a new subdivision. The developers had planted live oaks about 2 feet from the edge of the curb, in between the street and the sidewalk. I am sure the intention was that some day the trees would be part of a beautiful street tree canopy. It would have been better to plant the live oaks in the middle of the yard where they had plenty of space or plant a smaller tree in the space between the sidewalk and the street.
Before you plant a tree do some quick measurements to see how much room you have. A small maturing tree with less than a 20-foot crown spread needs about 200 square feet of space. A medium-sized maturing tree with a 30-foot crown spread needs 400-500 square feet of rooting space. A large maturing tree needs a minimum of 900 square feet of rooting space.
Planting too deep: The number one cause of tree decline for a young tree is the practice of planting too deep. If you look at trees in natural areas such as parks, you will notice that the part of the trunk where the roots flare out from the trunk is above ground. This zone where the roots begin is called the root flare. When we plant a tree the root flare should be visible and located slightly above the soil grade. If you take a look at the base of your tree and it looks like a fence post in the ground, it is more than likely planted too deep. A wise forester once told me, “Plant it high and it won’t die.”
Deep planting is a mistake performed by homeowners and landscape professionals alike. Deep planting encourages roots that will choke the trunk of the tree, as well as encourages disease and decay at the base of the tree by prolonging the time the trunk stays wet after rainfall or irrigation. It also reduces the amount of oxygen that tree roots need in order to respire. By planting so that the root flare is slightly higher than the soil level, the tree will gradually settle to so that the root flare is at the proper depth.
Not watering correctly after planting: Most newly planted trees do not get watered appropriately and take longer to become established in the landscape. Some trees do not become established at all and do not thrive. In order to grow well, a newly planted tree should receive about 2-3 gallons of water for every inch of stem diameter at every watering.
For instance, a 2-inch diameter tree should receive around 4-6 gallons of water at every watering. The frequency of the watering depends on the size of the tree and the amount of time after planting. Keeping with the example of a 2-inch diameter tree, it should be watered every day for 1 month, every other day for 3 months, then weekly until established. A larger tree requires a longer period of time to become established and therefore a longer irrigation period. If the soil is wet (as it probably is now) poorly drained, or the tree is dormant, the amount of irrigation should be reduced.
Over thinning: I often hear from homeowners that their arborist or tree trimmer wanted to thin out the center of the tree removing interior limbs and sprouts so that wind can go through the tree instead of against it. This is a common practice that sounds like a good idea but is actually very bad for trees. When a tree is pruned so that interior branches are removed it is called lion’s tailing.
You can tell a tree has been lion tailed when the sprouts and interior branches have been removed exposing the major branches, and all the growth is concentrated at the end of the branch. This type of pruning is harmful for two reasons. First it makes the tree more likely to be damaged by wind by concentrating the weight at the end of the branch. Second, it removes the ability to prune back to a lateral branch should you need to reduce the length of that branch in the future.
If you desire a more wind-resistant tree, proper pruning includes leaving interior branches and shortening the length of long branches by making proper pruning cuts called reduction cuts.
Topping crape myrtles: Southern Living Magazine coined the term “crape murder” many years ago to describe the practice of removing the tops of crape myrtle trees down to the large trunks. It is not known how this practice started but it has caught on like wildfire. Most folks do not know that it is not the proper way to prune crape myrtles. Often the crape myrtles are pruned in this fashion because they have gotten too tall. This practice can be eliminated if the proper research is performed prior to picking out a crape myrtle for your landscape.
There are over 1,000 different varieties of crape myrtle. These include trees that grow 2 feet tall and trees that grow over 30 feet in height. One can avoid having to top their crape myrtle by researching and choosing the variety that will grow to the height and color you desire. There is a great publication on pruning crape myrtle. It can be found online at: https://edis.ifas.ufl.edu/pdffiles/EP/EP39900.pdf.
Mulch volcanos: A 2-3-inch layer of mulch placed around the tree is one of the best things you can do to create a good rooting environment. However, it has become a common practice to pile the mulch up against the trunk in a layer several inches thick. The term for this is called a “mulch volcano” and it is harmful to the tree. It reduces the amount of oxygen that is available to the roots and promotes decay in the trunk by allowing the trunk to remain wetter longer.
A proper mulch ring should be as large as you can make it. Turf is a major competitor for water and nutrients and a large mulch bed 2-3 inches deep is good for the tree. However, the mulch should be pulled back a few inches from the base of the tree. This provides the trunk plenty of air circulation that allows it to dry out after irrigation or rainfall.
Over pruning palms: This seems to be an issue that will not go away. Over pruning palms can lead to wind breakage, insect infestation and reduced cold resistance. Many times, this type of pruning is called “hurricane pruning” and involves removing most of the tree crown and leaving a few fronds at the top. There is no reason to prune a palm in this fashion especially since our sabal palms are naturally one of the most hurricane-resistant trees we have.
Healthy palms have a 360-degree crown. Sometimes there are naturally dead fronds in the tree. If you need to remove dead fronds or the flower structures you can do that at any time. Other than that, it is recommended to not prune our palms any higher than horizontal. Good visual analogy is to prune no higher than 9 o’clock, and 3 o’clock on a clock face. For more on pruning palms go to: https://edis.ifas.ufl.edu/pdffiles/EP/EP44300.pdf.
If we treat them well, trees perform many valuable environmental services to our community. Eliminating the human caused problems that stress and weaken our urban trees will allow them to provide us with those services for a long time. You can find more information online from the University of Florida on tree care by going to: http://hort.ifas.ufl.edu/woody/.
Larry Figart is urban forestry extension agent from the University of Florida/IFAS.