We all want to do a good job taking care of the plants in our landscapes. Learning about the proper care a plant needs and providing it are key to successful landscape maintenance.
There are times, however, that we may unintentionally cause damage to landscape plants while trying to keep the landscape well-groomed and provide proper care.
Protect a tree’s bark, which can be compromised by string trimmers and other lawn-care equipment.
STAFF PHOTO BY TRAVIS SPRADLING
Save the bark, save the tree
Here’s a good example. A maintenance crew working on a homeowner’s landscape got too close to the trunk of a Japanese maple tree with a string trimmer and removed a lot of bark. The tree was looking poorly and the owner asked me what to do for it. Unfortunately, the damage was done, and there was really nothing she could do to help the tree. If the damage was bad enough, the tree could even die.
String trimmers and other equipment used for cutting down weeds and grass can be very damaging to young trees and trees that have relatively thin bark. If the line is allowed to hit the trunk, part of the bark will be removed with each contact of the line. If you are not careful, you might even remove an entire ring of bark all the way around the trunk, girdling the tree. Mowers pushed hard or dragged around the base of young trees can be almost as damaging.
The part of a tree’s circulatory system that carries food, manufactured by the leaves, to the roots (which can make no food for themselves) lies just under the bark. Damage that occurs when mowers or string trimmers remove patches of bark interferes with the tree’s ability to send food to its roots. As the roots are deprived of food, they begin to starve and function poorly — and this leads to a stunted, unhealthy tree. Remove a complete ring of bark and you may cut off food to the roots altogether. The roots starve to death, leading to the death of the tree.
Many sickly trees that have been planted for a few years but don’t grow well have been damaged in this way. Look at the base of their trunks and you will often see scars and callus growth from repeated injury done to the base of the tree.
In addition to interfering with food movement, the open wounds created by mowers and trimmers can provide entry points for disease organisms that can cause infections and decay.
To prevent these problems, do not allow grass to grow close to the base of young trees for the first three to five years after planting. And for thin barked trees like Japanese maples and crape myrtles, you must prevent damage.
Keep an area at least a foot out from the trunk grass-free — and farther out is even better. Keep the area mulched to prevent grass and weeds from growing. Any stray weeds can be killed with a quick spray of the herbicide glyphosate, if necessary (do not allow this herbicide to contact the trunk of the tree).
Not only does this protect trees from string trimmers, but keeping the area mulched and free from grass encourages faster growth on young trees. Research indicates that in some cases, trees that were mulched grew twice as fast as trees that were not. The major reason is competition from the grassroots.
Tree guards placed around the lower part of the trunk of young trees can also be used to prevent this type of damage.
Shrubs are generally planted in beds so are less at risk. But I have seen this problem occasionally when ground covers, such as Asiatic jasmine, are trimmed away from the base of shrubs with string trimmers, or when large shrubs like camellias are grown individually in lawn areas.
Whether you maintain your landscape yourself or pay someone to do it for you, don’t let this kind of needless damage happen to your trees and shrubs.
Mulching properly
Speaking of mulching around trees, it must be done properly. Mulch should never be piled up in a mound around the base of the trunk — a practice that has been dubbed “volcano mulching.”
Piling the mulch deeply around the base of the trunk exposes the trunk to dark, moist conditions. The bark was never meant to protect the tree from this kind of environment, and decay organisms can take advantage and invade the trunk.
When mulching trees, the mulch should be spread out in a flat disk 2 to 4 inches deep and pulled back slightly from the trunk. As the mulch thins out and decays, add more mulch as necessary.
Water trees using either a soaker hose or a traditional garden hose running on a slow trickle.
PROVIDED PHOTO BY RANDY LABAUVE/LSU AgCENTER
Killing with kindness
Overwatering and excessive fertilization are also issues for our landscape plants.
When dry weather occurs and irrigation is necessary, keep in mind that it is better to water thoroughly occasionally than to water lightly frequently. Be careful not to water excessively.
During the intense heat of summer, many landscape plants are stressed and become more susceptible to disease problems like root rot. Excessive moisture in the soil, which commonly occurs when plants growing in the ground are watered too frequently, is a leading cause of root rot in mid to late summer.
Fertilizing too generously is also not a good idea, but it is frequently overdone. High nutrient levels, particularly nitrogen, stimulate lush, vigorous growth that may look great, but may also be more attractive to insect pests or disease organisms.
Applying fertilizer is especially important when growing bedding plants or vegetables, which require generous nutrient availability to perform at the high levels we expect. Otherwise, be moderate in the amount of supplemental nutrients you provide.