(updated April 2017)
What is Oak Wilt?
Oak wilt is a vascular wilt disease caused by a fungus that infects the water-conducting tissues of oak trees and causes them to wilt and die. Good health does not improve resistance to this disease. If the oak tree is challenged by oak wilt, it can become infected. Prevention of Oak Wilt is easy. However, it is a very difficult disease to manage after it becomes established.
What causes Oak Wilt?
Oak wilt is caused by the fungus Ceratocystisfagacearum. In San Antonio and Central Texas, it is mostly a problem in Live Oaks and in Red Oaks such as Spanish, Shumard, and Blackjack. Live Oaks are a particular problem because of the common root system that develops from root sprouting. This connects all of the Live Oaks in an area with a common root system.
Oak wilt moves from location to location by the transport of a spore (a sort of seed) carried on the body of an insect. It travels from a spore mat produced on a Red Oak, to a fresh wound on another oak. The spore does not blow in the wind and cannot be carried by smoke.
Once oak wilt infects a Live Oak, it is moved from tree to tree through the common root system. It can also be carried from tree to tree through root grafts that can be formed between the same species. It is not uncommon for different species of oaks to form root grafts, allowing the disease to move between oak species.
What are the effects of Oak Wilt?
Leaf symptoms of oak wilt on Live Oaks are distinctive. The veins of the leaf turn yellow or brown while the rest of the leaf is green. We refer to this symptom as veinal necrosis (death of the vein) and it is considered diagnostic, Other symptoms include tip browning and leaf margin browning. These are non-diagnostic symptoms that also occur with other conditions such as drought or chemical burn. Once leaf symptoms occur, Live Oaks generally die within three months to a year. A few Live Oaks can survive for many years in decline. Leaf symptoms are difficult for most people to determine including most tree care companies. As a result, these companies treat trees erroneously or remove trees that are not infected. Buyer, beware! Before you sign a work order, get a confirmation from the Texas Forest Service or from someone that TFS has certified (TOWC, Texas Oak Wilt Certified).
Leaf symptoms in Red Oaks are much less distinctive, having none that are considered diagnostic. Red Oaks generally die within 30 days of the appearance of symptoms, leaving little time to react or confirm the disease. During winter and early spring, structures covered with spores can form just below the bark on infected Red Oaks. These structures are called spore mats and they are difficult to find. These spore mats produce the sticky spores that are carried by insects to fresh wounds on other oak trees.
Laboratory tests can be used to confirm Oak Wilt using the sap wood of a suspected oak. Negative results are currently only about 70% accurate.
How can Oak Wilt be prevented?
Prevention of Oak Wilt is easy:
- Paint all pruning cuts and injuries on Oaks.
- Avoid pruning oaks during the spring.
- Do not bring contaminated firewood on to your property.
Paint or treat all wounds on Oaks within a few hours. Treating wounds after three days has no effect. You can use latex paint (our preferred choice), hair spray, Elmer’s glue, mud, shellac, you get the idea. Get the wound covered. The size of the wound does not matter, treat all pruning cuts. If you cannot treat it, do not cut it! Strangely, we do not recommend the use of pruning sealers (except to seal clay pots) because the sealer is too thick and can result in other problems. You can use the cheapest latex spray paint you can find and color is not important. We know of no benefit to painting wounds or cuts on other species of trees, so oaks are the only trees that need treatment.
When possible in San Antonio, avoid pruning oaks during March, April, and May. Those months generally have good conditions for the presence of spore and for high populations of sap feeding insects. That does not mean you cannot prune in those months to remove broken branches or branches that are hitting the roof of your house or car. If you must cut a limb, paint the pruning cut. If you have a choice or if you are doing routine pruning, avoid pruning in the spring. The safest time to prune is during hot weather from June through Thanksgiving or some years thru Christmas. It is also safe during cold weather when insects are inactive. Even during safe times, paint all pruning cuts regardless of size. If you cannot paint it, do not cut it!
The transport of firewood is probably responsible for most new oak wilt centers. During storage, insects can emerge from the transported wood and infect nearby trees. Or spore mats can form on fresh Red Oak during storage. Burning of the wood is not the problem as oak wilt does not spread in the smoke. Firewood cut from trees growing on your property is not a problem. The problem is wood brought in from other locations. A lot of firewood is coming from oak wilt centers where it is cheap or free and easy to obtain. If you can easily remove the bark with your fingers, the wood has cured long enough to be safe. The recommendation to cover suspicious wood with clear plastic to trap or kill insects is not wise. Do not purchase or transport firewood that is not safe. Just like Jurassic Park, life has a way of escaping. If you are going to cover the firewood with clear plastic, it is not safe and you should not buy it or transport it.
What are the Treatments for Oak Wilt?
Oak wilt is not an easy disease to manage once is gets on your property or in your neighborhood. Rarely, we are able to discover the infection in the first tree, before the disease has moved into the root system, and the total removal of that tree stops the disease. Once two or more oaks are involved, trenching usually is the only effective way to contain the disease center. Trenches are installed 100 to 150 feet beyond trees showing symptoms, completely enclosing the infection center. You can imagine the mess, destruction, and coordination problems to accomplishing this. Trenches need to be at least five feet deep. The purpose of the trench is to cut all root connections. The trenches can be filled as soon as they are made.
Fungicide injection or infusion is limited in value and effect. The results of injection with propiconazole (Alamo) are random and varied. Basically, it is our only treatment option and it can extend the life of an infected tree on your property, sometimes upwards of ten years. Occasionally (rarely) we get a cure. It has some worth as a preventive, but will not stop the movement of the disease through the roots into non protected oaks. It is not reliable, predictable, or guaranteed. It is expensive and needs to be repeated about every two years. Unless you have a large budget, you need to be selective with the trees you choose to inject and you need to be prepared for limited or no success.
There are several new generic (less expensive) mixes with propiconazole that have the same percent active ingredient. We have little experience with these mixes and we have no confidence in them. They are causing the cost of Alamo to come down dramatically (yea!) and we have chosen to stay with Alamo.
Our experience with micro-injection has been absolutely dismal. We have observed several other companies using micro-injection and they have had absolutely no success. Current research shows no success with micro-injection. We would all like to use this method because it is easy and neat. But, it does not work.
There are other oak wilt treatments being sold, miracle treatments using secret ingredients. None of them has shown any long term success. Most of them use fertilizer to make a tree look better for a short time and have no effect on oak wilt.
There is promise with Systemically Induced Resistance (SIR) using Trichoderma fungus obtained from whole ground corn meal Recipes are available at www.Dirtdoctor.como We are now including corn meal tea soil drenches (1 cup corn meal per gallon water) with all propiconazole injections and we are doing tea drenches on oaks that clients choose not to inject. First year results are encouraging, but this is very early in our research.
The TFS Oak Wilt Suppression Project was designed to assist you with oak wilt management. They expanded this program and are training certified arborists to help them identify the disease and develop management approaches for individual property owners. The original training certified arborist as Texas Oak Wilt Certified (TOWC) and they were listed on their web site, www.texasoakwilt.org. Current training just initiated in 2017 qualifies the arborist as Texas Oak Wilt Qualified and requires retraining or re-qualifying every 5 years.
David M. Vaughan
Certified Arborist TX 0118
The most likely cause of tree problems in the urban setting in our area is buried root collars. I seldom have a day in which I do not diagnose a root collar disorder. In my experience, it is by far the most common cause of tree decline and death and is responsible for most of the secondary pests and diseases we encounter. Into this root collar disorder category, I also group all the girdling problems such as girdling roots, girdling straps and twine, girdling wire baskets; and containers such as plastic pots, nylon bags, and felt bags that are not removed when a tree or shrub is planted.
The root collar is the area of a plant where the trunk or stem joints the roots. Tree have a noticeable flare at the root collar that we call the root flare and we want this flare to be visible and exposed to the air.
The trunk and root flare of a tree are not genetically programmed to resist constant soil moisture. Respiration occurs in this area of the tree (the exchange of oxygen and carbon dioxide) and constantly wet bark restricts or stops this gas exchange. Over a period of time, this restriction causes this area of the tree to function poorly, interferes with the downward movement of food to the roots, and eventually results in root dieback and reduced water uptake. These trees are more susceptible to disease infection, insect invasion and to stress caused by drought or compaction or irrigation excess.
Early symptoms of root collar disorders include yellowing of leaves, margin burn or necrosis of leaves, and dieback in the upper canopy. These are the same symptoms we see from water stress (both too much and not enough) and most of us react by watering the tree which usually makes the problem worse. Often, we see no early symptoms and we get the phone call that starts out with my tree died overnight. My tree was fine on Friday and was dead on Monday. That kind of rapid death is almost always caused by a root collar disorder. The tree exhausts its reserves, often looking OK, and dies overnight. The problem that led to that rapid death has been going on for years. And it is not uncommon for that overnight death to occur 1 to 3 years after the installation of an irrigation system.
Checking for a root flare is easy, you can see it. If it is visible, the problem is something else. If you can not see it, you have found the most likely cause of your tree’s problem. The soil or mulch needs to be removed down to the level of the root flare and out away from the trunk of the tree about 6 to 12 inches. The distance away from the trunk is not critical as long as the trunk and root flare are exposed to the air. You will find that the deeper you have to dig to reach the root flare, the further out from the trunk you will dig just so you have room to work. Most excavations are 6 to 12 inches deep but we have one tree that is doing well that excavated about 7 feet deep!
Do not use a shovel or pick to excavate around your tree. Do not scrape or scar the roots. Use a hand trowel or rock hammer. You can also excavate with water pressure; it’s messy but very effective for shallow excavations. We use an air spade which removes soil with air pressure, does not damage the roots, and allows us to stand while we excavate. You will appreciate the standing after you have tried to dig a tree by hand. As you excavate, you should correct girdling problems caused by tree roots or things that were left on the tree when it was planted. Sometimes, you can not correct all of the girdling roots and will need to return in a year or two to correct additional girdling roots.
Severely declining trees need to be removed. Do not waste your time and effort trying to save a hazardous tree.
The well you’ve dug should remain open. There are many options for edging or lining the well to help keep soil from falling into the well and to make the well attractive. If the well is a safety hazard, it can be filled with large, course gravel, but that gravel will need to be removed and replaced every 3 to 5 years. It is best to leave the well open, the root flare exposed to the air.
The excavated tree should be fertilized with a good organic fertilizer or a good slow-release fertilizer or one of the good organic sick tree treatments that are available at better nurseries.
You may need to water the tree but you should be very careful. Our native or adapted Texas trees are very capable of dealing with drought. They are not well adapted at dealing with too much water. Be very careful with how you water because your trees are usually better off with dry conditions. We normally recommend that you water to keep your grass, annuals, and shrubs healthy and do not irrigate established native trees.
In our experience, root collar disorders are by far the most common reason for the decline or death of our landscape trees. Proper planting and careful use of fill soils for leveling and for landscaping are important to preventing this disorder. If the disorder already exists, excavation to expose the root flare to the air can often save your tree.
David Vaughan is a Certified Arborist with Etter Tree Care.
Soil is more than sand, silt, and clay with some small amount of organic matter. You may have 3 inches of clay over caliche, or 12 inches of blackland clay, or 5 feet of sand over hardpan. Whatever you have, soil is teaming with life.
Experts estimate that a tablespoon of forest soil contains 6 billion microorganisms consisting of 75,000 species of bacteria, 25,000 species of fungi, 1,000 species of protozoa, and 100 species of nematodes. And that is not a typo; that is number of species.
James Urban in Up By Roots uses a cup of soil (that’s a handful for me) and has numbers in the billions; 200 billion bacteria, 100,000 meters of fungi (that’s about 60 miles!), 20 million protozoa, 100,000 nematodes, 50 micro arthropods. That’s not much soil to contain such mind boggling numbers. The numbers are so large, so extreme; I do not think they register with most of us. It’s hard to imagine how small you have to be to have 200 billion in a handful of soil.
Under good conditions bacteria have the ability to multiply or divide every 20 minutes. They could quickly overwhelm the soil unless billions of them were consumed every hour. A protozoa can consume 10,000 bacteria a day and there are 20 million protozoa in a handful of soil. Nematodes eat bacteria, some protozoa, and a lot of fungi. Arthropods eat all of the above. Fungi consume nematodes, decompose the bodies of whatever dies, decompose organic matter, and release nutrients from soil particles and rock. Bacteria also decompose organic matter and release nutrients from soil and rock. All are completely dependent upon carbon which can only be supplied by plants.
This is the soil food web. The entire process protects nutrients from leaching out of the root zone of plants by securing nutrients within the bodies of microbes. Plants and trees are very particular about the nutrients they absorb and prefer nutrients in a form that has been manipulated by microorganisms. The nutrient needs to be consumed by a bacteria that is then consumed by a protozoa or nematode and then pooped out in the rhizosphere in ion form. The rhizosphere is a small zone of intense biological activity about 2mm wide (1/10th inch) around a root. Only then is the nutrient in a form that the plant root can absorb. So bacteria put out enzymes that release nutrients that they absorb. A protozoa consumes the bacteria, uses what it needs and releases the leftovers which have been converted into a form plants can use. If the waste is released in the rhizosphere, the expanding root is able to pick it up thru diffusion.
In exchange, the plant provides carbon sugars it has produced during photosynthesis. About 40% of what a tree produces in its leaves is leaked out thru roots to nourish the bacteria and fungi around those roots. That is a lot of product being leaked, an indication of how much our trees depend upon the micro soil food web. The bacteria depend upon their sugar daddy and crowd in on the expanding root like pigs at a feeding trough, forming a physical barrier that excludes bad bacteria. When things are healthy, the bad guys do not have access to the root or to the sugars. When things are right, the good guys out compete the bad guys, limiting the numbers that could cause trouble.
Fungi can also form a physical barrier around a root, so thick that nematodes and other bad guys are excluded. Many of these fungi are mycorrhizae fungi that are attached to the root or have structures inside root cell outer walls. The tree provides carbon sugars to the mycorrhizae in exchange for water and nutrients, especially phosphorus. Fungal hyphae can be 1/60th the size of an expanding root and have the ability to get water and nutrients from very small pore spaces in the soil. Mycorrhizae fungi are able to deposit water and nutrients directly into the plant root where the water and ions move through a cell membrane into root cells.
Fungi eat or consume nematodes. Some form snares with their hyphae, put out a nematode attractant, and close the snare when a nematode enters the trap. They then grow a special structure that penetrates the sightless worm to consume the groceries. Other fungi produce a poison that kills the microscopic worm when the toxin touches its mouth. Some use glue to glue trap the worm.
And then there are the arthropods (mites). They are the big guys in this micro world, eating fungi and nematodes and protozoa. And all these guys are pooping nutrients in forms that plants can use. Many of these waste products get picked up and consumed enough times in this soil food web to become fairly stable compounds which are how humates are formed.
Trees and plants are completely in charge of this system. They have the ability to change the sugars they provide to stimulate certain bacteria or fungi according to their needs. They change the sugars they produce by season, by temperature, and by moisture levels. If they need iron, they produce a sugar to stimulate the fungus or bacteria that can provide that need. Low on water and they stimulate the mycorrhizae fungi to bring in more water.
Bacteria could easily be washed away so they glue themselves to soil particles. They use organic glues produced from the sugar compounds supplied by plants. These glues are similar to the ones produced by the bacteria in your mouth that cause morning mouth and tartar. Clay particles tend to be rod shaped and bacteria can glue these end to end forming odd shaped structures that can resemble a snow flake. This is the smallest soil aggregate and it protects the bacteria and provides space for the slow movement of air and water. In sandy soils bacteria form cup like aggregates which hold water.
Fungi need to protect their reproductive structures from grazing arthropods, so they weave or glue several of these bacterial soil aggregates together and hide their fruiting structures inside. The glue they use is called glomalin and it is responsible for about 33% of the carbon found in soil when mycorrhizae fungi are present. This forms a larger soil aggregate, still too small to see with anything other than a high powered microscope. Millions of these are formed within a handful of soil and they are an important, critical component of soil structure. The movement of nematodes and arthropods create small passages that also provide for the slow movement of air and water. These are the aggregates we destroy with compaction, plowing, tilling, and double spading our gardens. Once these small aggregates are eliminated, water or air will not pass through. If you want your soil to be healthy, you should not see it very often. Keep your soil covered with plants and undisturbed.
Trees and their roots can get lazy. When we provide nutrients to plants in forms they can use with very little biological activity, the tree will reduce the exudates it releases, which reduces the population of the good guys and can give the bad guys access to our plants. It makes plants dependent upon chemical fertilization. Fertilizers with high salt content (quick release and water soluble) can desiccate bacteria and fungi and can irritate worms causing them to leave the area.
We need to regard soil as a complex system of living organisms and seriously think about becoming microbe farmers, like the trees in a climax forest. With the exception of pH, the physical properties of soil are not nearly as important to a gardener or arborist as the invisible living microbes occupying the soil. Your top priority in caring for soil should be to protect and preserve the soil food web.
This article was based on the incredible work of Dr. Seuss in his landmark soils manual, Horton Hears a Who with help from Up By Roots by James Urban, The Soil Will Save Us by Kristin Ohlson, Teaming With Microbes by Jeff Lowenfels and Wayne Lewis, the Certified Arborist Study Guide, Teaming With Nutrients by Jeff Lowenfels, and Teaming With Fungi by Jeff Lowenfels.
David M. Vaughan
Certified Arborist TX 0118
Member American Society of Consulting Arborists
Organic Certified, Texas Organic Research Center
PRUNING, when properly performed, is beneficial and can reduce the risk of stem and branch failure; provide clearance for structures, vehicles, and pedestrians; improve health and appearance; and improve views. Improper pruning techniques are harmful for a tree’s health, vigor, stability, and appearance. A tree that is not pruned, or left natural, can develop low limbs, co-dominant stems, defects such as included bark, and accumulation of dead branches.
Before pruning, determine the reason and objectives that should result. For example, young trees, trees twenty-five years or younger, are pruned using different objectives than mature tree (trees older than twenty-five years). On average, young trees should be pruned about seven times during their first twenty-five years after planting.
Remember, when pruning Oak trees you must paint your cuts, this includes all wounds any size, at anytime during the year! This rule applies for all species of Oak and to wounds made, for example, from a weed eater or lawn mower. Any latex based paint works well, the color doesn’t matter.
I. Pruning Young Trees
The objectives for pruning young trees are to:
- Establish and develop one dominant leader
- Space main, scaffold limbs
- Keep low, non-permanent branches small
- Select lowest main scaffold branch
- Prevent all branches from growing larger than half the trunk diameter
- Maintain a live crown ratio of greater than 60%
Please Note: Prior to planting your tree, establish the root flare of your tree to ensure it is planted at grade and that there are no girdling roots present. It is important to visually inspect the root flare of your tree annually and at each stage of pruning to ensure the root flare remains visible and that no girdling roots have developed.
First Pruning – Pruning at Planting: Trees that are less than four inches in diameter do not have any permanent branches. It will take many years for the permanent branches to develop. Shorten or remove all branches competing with the one leader that will make the best main stem. Remove broken, cracked, damaged or dead branches. Do not remove more than twenty-five percent of the live foliage at planting.
Second Pruning – Two Years After Planting: At this point, there still may not be any permanent branches, especially on trees less than four inches in diameter. In order to establish a dominant leader, shorten or remove all competing leaders and branches four inches in diameter or larger within twelve inches of the largest diameter branches in the top half of the tree. Shorten, or reduce, low, vigorous branches to improve clearances.
Third Pruning – Four Years After Planting: Most branches are temporary even four years after planting and will eventually be removed from the tree. Shorten or remove any leaders competing with the dominant leader you have selected. Reduce or remove low vigorous branches for clearances. Continue to space upper canopy branches about twelve inches apart and reduce or remove branches in between. There should be only one large branch per node. If limbs are clustered, or have more than one branch per node, select the one branch that will remain and shorten or remove the competing branches. Do not remove more than thirty-five percent of the live foliage.
Fourth Pruning: Eight Years After Planting: Shorten or remove any leaders competing with the dominant leader you have selected. Select the lowest permanent branch and shorten any branches below this limb to reduce their growth. Branches below the lowest permanent branch should be removed when they are about half the size of the trunk and after the bark in that area of the trunk has become thick and grooved, or once a branch bark ridge has been established. Continue to space upper canopy branches at twelve to eighteen inches apart and reduce branches in-between. The goal is to have only one branch per node, no clustered branches. Do not remove more than twenty-five percent of the live foliage.
Fifth Pruning – Fourteen Years After Planting: Shorten or remove leaders competing with the dominant leader. Select several permanent scaffold branches and reduce branches within eighteen to thirty-six inches of these permanent branches. Shorten or remove branches below the permanent scaffold branches.
Sixth Pruning – Twenty Years: Shorten or remove leaders competing with the dominant leader. Continue to identify permanent scaffold limbs and shorten branches that are between these branches, remember the goal is to have one branch per node. Reduce or remove branches below the first permanent scaffold branch.
Seventh Pruning – Twenty-five Years: Perform the same procedures as the previous two prunings.
These seven pruning sessions accomplished within the first twenty-five years after planting will aid trees in developing good structure, enabling them to cope with high winds and most other stresses. Proper planting and good irrigation until the tree is established may allow you to prune less frequently.
II. Pruning Mature Trees
Mature trees are usually pruned to reduce risk of failure and to provide clearances from structures and through-ways. Occasionally mature trees need to be pruned to allow more light to the ground and for the health of the tree. Ball moss removal is not pruning and should not include the removal of live branches. The different types of pruning for mature trees can be performed in the entire tree or in sections of the tree depending on what needs to be accomplished.
Structural Pruning: Structural pruning either continues young tree pruning or initiates pruning to develop one dominant leader. Trees with one dominant leader and small, well spaced branches are less likely to suffer mechanical failure, and can more effectively compartmentalize the spread of decay within the tree. Structural pruning selectively favors a single, dominant leader by suppressing competing leaders using reduction cuts. Reduction cuts shorten stems back to lateral branches at least one-third the diameter of the cut stems. Reduction cuts may need to be done every few years to encourage more growth in the selected leader, and should be performed on tree species that will become large at maturity to: promote longevity, decrease future maintenance costs, and in order to reduce conditions in the tree that could cause harm to people or property.
Thinning: Thinning reduces the density of live branches, increases light penetration to the interior of the canopy and to the ground below the tree, and increases air movement through the canopy for disease control. Thinning is also performed for safety reasons. For example, if performed properly, it can reduce the wind-sail effect or aid in weight reduction pruning. Proper thinning retains the shape of the canopy and does not remove interior living branches. Removing interior foliage, or lions-tailing, has adverse effects on a tree and should be avoided.
Thinning should result in an even distribution of branches by removing some of the branches from the edge of the canopy, not from the interior. This type of pruning should not remove more than about fifteen to twenty percent of live foliage in a mature tree and often five to ten percent is enough. For young trees, up to twenty-five percent live foliage can be removed without harm. Thinning is a delicate process that removes small diameter limbs, usually in the one to two inch size. Once completed, it may be difficult to tell that the tree was pruned and it should have most of its live interior growth.
|Appropriate cut||Inappropriate cut|
Reduction Pruning: In the urban setting, trees often grow larger than the space they can occupy. Reduction pruning is often used to reduce the size of a tree by decreasing the length of one or more branches. It is also used for clearances and to reduce risk when a limb has become hazardous. Reduction pruning reduces size while attempting to maintain a tree’s form.
When performing reduction cuts, limbs are cut back to their point of origin or back to a lateral branch that is large enough to sustain the limb and to assume apical dominance. A common rule of thumb is the lateral branch should be at least one third the size of the removed portion; we normally like to select lateral branches at least half the size of the removed branch. Most of the removed branches will be two to six inches in diameter. Never reduce a landscape tree by topping it! Topping causes a number of problems such as: decay, numerous sprouts, cracks in limbs, root decline, and bark defects, just to name a few!
Raising or Lifting the Canopy: Low branches are usually not desirable on mature trees in the urban setting. Low branches can be kept small using reduction cuts until they are removed. Upright growth from these low, undesirable branches needs to be removed.
Canopy raising, or lifting, is performed on young and middle aged trees to prevent low, non permanent branches from growing to a large diameter. These branches are valuable to the tree because they help increase overall growth and they improve trunk taper, which increases trunk strength. Branches below the lowest permanent branch should be removed when they are about half the size of the trunk and after the bark in that area of the trunk has become thick and grooved, or once a branch bark ridge has been established. Regular reduction cuts suppress limb growth while the branch bark ridge forms, until they are later removed. This simple technique is less damaging for the tree because it prevents having to remove large limbs at the main stem.
Crown or Canopy Cleaning: Crown Cleaning includes the removal of dead, diseased, detached, and damaged branches. Crown cleaning is normally performed on middle aged or mature trees for the safety of people and property and to make the tree more attractive. Crown cleaning can also be used to shorten branches with included bark to reduce the risk of failure and to address limbs with cracks or other structural defects. A few water sprouts, or “suckers” can be removed but most of the sprouts should remain, removal of all internal sprouts can be very damaging to a mature tree.
III. Pruning Palms
Palms and cycads need regular pruning to keep them attractive and safe. Many palms maintain a set number of live fronds. For palms, a regular turnover of foliage occurs as dying lower fronds are replaced by new ones. Dead fronds are not harmful to the Palm tree but they are a safety hazard, can provide shelter for all kinds of unwanted pests, and can become a fire hazard. An excessive amount of older yellow fronds could indicate a nutrient deficiency of either: potassium, magnesium, or manganese. Determine the cause of the problem because pruning or fertilizing with high nitrogen or the wrong type of fertilizer will only worsen this problem.
Before pruning palms, determine the reason you are pruning and the objective you want to accomplish. Remove dead and dying fronds and developing flowers and fruit. It is better not to remove live, healthy fronds, however, if you must remove healthy fronds, avoid removing fronds that are growing upward and be careful about removing fronds growing horizontally. Excessive live frond removal can permanently reduce the set number of fronds a palm maintains. When removing a frond, sever the frond close to the petiole base.
There is little reason to shave or strip the trunk smooth, although it does no harm to the palm. The pineapple shape crafted at the base of date palms is not necessary for good health.
Illustrations, PowerPoints or photos by Edward F. Gilman, Professor, Environmental Horticulture Department, IFAS, University of Florida.