In the last couple of weeks, I’ve had multiple questions regarding trees and shrubs that aren’t looking too hot. These types of calls are common this time of year – it has gotten hot and dry, and plants have fully emerged from winter, causing issues that have been hiding under the surface during the dormant season to manifest as crown or branch dieback. While there are a wide variety of things that can cause dieback, in most cases a little detective work can help pinpoint the issue. Let’s look at a few of the most common causes of dieback and some corrective measures that may help restore the plants to health.
The first thing to do when you notice a plant in decline is nothing. Don’t try and oversaturate it with water. Don’t run out and dump a bunch of fertilizer around it. Many times, these panic measures exacerbate the stress the plant is already under. Instead, I encourage you to give us a call at your local UF/IFAS County Extension Office. We can likely help identify the cause of the problem through a site visit to your property or by you sending us diagnostic photos of the plant with a description of what’s been going on with it – the more information you can provide about the plant and the management practices it has experienced, the better (you can email diagnostic images/information to d.leonard@ufl.edu).
The most common cause of tree/shrub dieback that I see arises from improper planting practices. Most landscape plants should be planted at or just above the surrounding soil level, preferably where the topmost root arises from the trunk. To accomplish this, planting holes should be dug slightly shallower than the rootball’s height and about twice as wide. Planting any deeper than that is probably too deep and can cause problems like trunk and root decay, which lead to crown dieback. Unfortunately, once a plant is planted too deep, it cannot be corrected other than digging up and replanting at the proper depth, which may or may not be possible depending on the size of the tree. Another common issue that can arise after planting is girdling roots. This occurs when plants are grown in plastic containers and develop a root system that circles the inner wall of the pot. If not trimmed, the plant’s root system will continue to grow in this manner, eventually encircling the plant’s trunk, cutting off water and nutrient flow, and leading to crown dieback. Fortunately, this condition can be prevented by cutting, removing, or redirecting these roots at planting.
The next most common cause of plant dieback occurs due to soil disturbance by people. It’s easy to forget but the root zone of trees and shrubs can reach out several times farther than the plant is tall and is easily damaged. Disturbances to the root zone from digging or trenching near trees or compaction from prolonged vehicle travel over the area cause damage that might be slow to appear but can lead to plant decline. If you are doing construction or building near a shrub or tree, try to keep digging machinery as far out of the root zone as possible and avoid repeatedly parking or driving vehicles over the root zone area. Like below ground root damage, trunk damage that occurs from injury by string trimmers, mowers, or animal feeding activity can all disrupt the flow of water and nutrients in plants and prove deadly. There is no cure for this type of damage, so employing physical barriers to prevent damage is key.
The last major stress is environmental in nature and is caused by a water imbalance – either too much or not enough. Dry soil conditions during the planting and establishment phases (first several years after planting) should obviously be avoided if possible – keeping the developing rootzone moist and allowing plant roots to establish in their native soil is critical. Too much water can also cause problems for trees planted in poorly drained soil. Excessive moisture leads to root diseases, which ultimately presents as dieback in the canopy. If planting in an area that tends to stay wet, select a species of plant adapted for that sort of site – some species are more tolerant of “wet feet” than others. While many people expect disease and insect damage to be the cause of an unhealthy plant, they’re often not the biggest culprit and, if they occur at all, are generally secondary to one of the above issues.
It is the time of year when we get reminded that we have just entered Hurricane season here on the Gulf Coast. Ideally you will have already done your tree maintenance and health checks around your home, but if you have not you can still get a tree care professional out to look at your trees. Maintaining your trees is an important part of storm preparedness. Keeping trees trimmed and in good health ensures that tree risks are minimized during the storm season. Even with proper pruning and maintenance some trees pose a risk due to location, poor structure, or disease. Having a professional assess your tree/trees and come up with a maintenance plan can help you avoid costly damage and keep your tree in good condition.
In this file photo released by UF’s Institute of Food and Agricultural Sciences, Associate Dean for Research Mary Duryea and Ed Gilman, a UF urban horticulture professor, look over their recently published booklet that gives tips on how to prevent storm damage to urban trees. The booklet is free and available on the Internet or at any county extension office.
Trees are a major part of our landscape on the Gulf Coast, especially in our urban areas. They provide so many benefits to the landscape and are often the centerpiece of yards and parks in our urban areas. Without trees we lose the shade and cooling benefits a tree provides, have less habitat for birds and other wildlife, and loose aesthetic values that come with a majestic tree. Trees take a long time to grow and develop as well, so a large well-developed tree is not easily replaced. This naturally leads to a question many people find themselves facing. How do I preserve trees I want but minimize risk to my home and structures? The answer to this question is to assess the condition of the tree, the risk it may pose, and decide on the proper tree maintenance accordingly.
Lots of things go into determining what to do with a tree. The first thing to consider is location of the tree and its limbs. If the tree and its limbs are close to your home, you must consider how to maintain the tree in such a way that risks are minimized. If the tree has structural and/or health problems, you must factor in how these conditions affect the stability and health of a tree. The tree species also determines how it will need to be maintained as well as how stable it is in a wind event. All of these factors play into how to maintain the trees on your landscape, or if the tree poses an unacceptable risk, when to remove trees that may be in decline or present a hazard.
The best course of action is to consult with a tree care professional and develop a tree maintenance plan. Make sure you select a tree care professional with good qualifications, background, and insurance. The top professional credential in tree care is the International Society of Arboriculture’s (ISA) Certified Arborist. You can search for a Certified Arborist in your area on the ISA Website, Find an Arborist (treesaregood.org). For trees that you are concerned about from a risk perspective consider getting a Tree Risk Assessment. Certain Certified Arborists carry a Tree Risk Assessment Qualification which is a specialty qualification specifically to assess the risk a tree poses. By having your trees examined by an arborist you can make an informed decision on maintaining your landscape trees. For trees that are in good health and are species that do well in high winds, proper maintenance and pruning will assist in keeping the tree in good condition. For trees with health or structural problems or that are species that do poorly in high winds, removal may be needed.
There is no one size fits all solution to tree maintenance and tree risk, but with proper assessment and tree care you can be confident you are making the correct decision. Putting off tree care and assessment is when problems occur. Consulting with an arborist and developing a tree care plan with clear timelines and practices is your best option to maintain your trees and avoid issues with high-risk trees. As painful as it may be, for high-risk trees removal and replacement may be the best option. By consulting with a tree care professional, such as an arborist, you can know your tree conditions and the associated risks and options. With this information in hand, you can make well informed decisions that match your tree health and risk management goals.
Many future problems can be avoided by paying attention to tree selection, planting and maintenance in Florida’s high wind climate. We may think of tropical storms causing tree damage but our typical summer thunderstorms can produce winds in excess of 50 miles per hour with downbursts reaching over 100 mph.
There is no way to protect trees from all storm damage. Trees are not adapted to worst-case storms, such as Hurricanes Michael or Ian, only to our average wind climate.
It’s wise to take time to select and correctly plant the right trees for North Florida.
Past hurricanes have taught us that large growing trees planted too close to curbs, sidewalks or buildings blow over easily because they don’t have adequate room to develop a sound root system. It’s best to either plant these trees farther away, plant trees that may stay small, or increase the size of space allocated for tree root growth.
Research and storms have taught us that tree roots need large soil spaces for strong, stable growth. The more rooting space trees have, the less likely they are to fail. Strong root growth is essential for tree stability and health. Large maturing trees need at least 30 feet by 30 feet (900 ft. sq.) of rooting space. Many construction practices such as paving over roots, raising and lowering soil grade, and soil compaction from equipment result in root injury for existing trees, making them less durable and less stable.
Magnolia Tree in the Landscape. Photo courtesy Stephen Greer
Studies have also shown that trees growing in groups better survive high winds compared to individual trees. A group was defined as five or more trees growing within ten feet of another tree, but not in a row.
A short list of large maturing, storm resistant trees to consider include live oak, sand live oak, bald cypress, pond cypress, black gum and magnolia.
Do some homework and take a look at tree species that have done well in your area. If you don’t want or need a large tree in your yard, there are many small and medium sized wind-resistant trees from which to choose, like Crape Myrtle and Vitex. Many palms are wind resistant too, particularly the cabbage palm.
Having success with trees in the landscape involves starting with healthy, well-developed trees. Plant the right tree in the right place. Follow good planting procedures, including not planting trees too deep and providing adequate root space to allow for strong, healthy root growth. Practice correct maintenance techniques, which includes learning how to prune to produce a structurally sound tree. Finally, consider if it is time to be proactive and have large over-mature, declining trees removed and replaced before the next storm.
This is the time of year when we often see crapemyrtles unnecessarily topped: main stems that are several years old are cut back, often leaving branch stubs 2 – 5 inches or more in diameter. Topping is sometimes called heading, stubbing, rounding and dehorning.
Figure 1. Topping is the drastic removal of large-diameter wood (typically several years old) with the end result of shortening all stems and branches. Topping crapemyrtle is often referred to as “crape murder” because topping usually is not recommended for crapemyrtle. Image Credit Dr. Gary Knox
Figure 2. Topping is the drastic removal of large-diameter wood (typically several years old) with the end result of shortening all stems and branches. Topping crapemyrtle is often referred to as “crape murder” because topping usually is not recommended for crapemyrtle. Image Credit Dr. Gary Knox
In the case of crapemyrtles, another name for this practice is “crape murder”. Topping a crapemyrtle is almost always unnecessary. Because people have seen this done in previous years, home owners often mimic this practice in their own yards, not realizing the unfortunate consequences.
Research at the University of Florida, detailed in this linked publication, found that topping crapemyrtle (“crape murder”) delays flowering up to one month. In other words, unpruned trees may begin flowering in June whereas topped trees don’t flower until July. This research also found topping reduced the number of flowers and shortened the flowering season. Finally, topping stimulated more summer sprouting from roots and stems. Sprouting results in greater maintenance since sprouts are usually removed to maintain an attractive plant appearance.
Unfortunately, landscape professionals and home owners often must maintain crapemyrtles that others planted, and so must deal with the consequences of poor cultivar selection and/or placement. If a crapemyrtle requires routine pruning to fit into its surroundings, it should be replaced with a smaller maturing cultivar. Dwarf crapemyrtles mature at a height of 5 feet; medium crapemyrtle cultivars grow up to about 15 feet in height, and tall or tree-size crapemyrtle cultivars exceed 15 feet and often grow to 20 – 30 feet tall in 10 years.
Best locations for crapemyrtle are areas in full sun with plenty of room for the cultivar size and away from walkways and roads. Proper selection of crapemyrtle cultivar and proper placement in the landscape can result in a low maintenance crapemyrtle without the need for significant pruning.
Figure 3. With proper cultivar selection and placement in the landscape, crapemyrtle develops into a beautifully shaped tree that rarely needs pruning. This crapemyrtle is ‘Muskogee’. Image Credit Gary Knox
