The crown of a tree is the leaf bearing twigs and branches and the spreading green foliage that we see. A heathy, full crown is a good indication of a healthy and vibrant tree. The crown and the foliage it supports is the energy collector and the center for photosynthesis, which is how the tree produces the energy it needs to live. For a tree to live and thrive, a full crown of leaves is essential, and an unhealthy and thin crown is an indicator the tree has issues. Crown dieback is often not noticed until it is relatively severe and at that point it can be too late. If a tree drops below a certain percentage of live crown it can no longer support itself and continues to decline. The good news is that if you notice your tree is starting to show signs of crown thinning and dieback you can likely intervene to improve its health or diagnose a problem early.
Tree Showing crown dieback, note the dead branches and lack of foliage on the outer branch tips. Photo Credit-Ian Stone
Crown dieback, which is also referred to as crown decline, is a progressive issue that starts small and can progress to the point that only small sparse areas of foliage are left. It is a tree’s response to various stressors, including environmental conditions and severe rot/decay. As a response to severe stress, the tree begins to abort part of the leaves and some of the small branch tips. If the stress continues to worsen, the tree will continue to abort more of the crown, producing progressively more dead wood. The tree is essentially trying to prune itself back to a manageable level of foliage based on the stress it is encountering. This can occur in both small, young trees and mature, established trees. A variety of conditions cause the stress that begins this process. For instance, you may notice crown dieback in young trees planted in compacted urban conditions such as parking lots and paved areas. Trees in these conditions experience stress from the compacted soil and encounter subsequent issues with water and nutrient stress. Large mature trees in an area that experienced recent construction may also exhibit dieback, especially if buffers and setbacks are not maintained or significant fill dirt is brought in. Issues from root disturbance and compaction cause stress and root dieback, which in turn causes visible crown dieback. Additionally, trees that are experiencing rot, decay, and other vascular disease issues will often begin to exhibit dieback. As the rot or vascular disease progresses, the tree is less able to transport water to the crown, which results in the crown dieback that can be seen as the crown thins. Often, in cases of rot, crown dieback will be the primary visible symptom that rot is occurring, as the rot can be concealed deep in the tree. While multiple stressors can be the cause of crown dieback, it is a clear indicator a tree is stressed and in trouble. If this condition goes unnoticed, it can progress past the point that the tree can be saved. However, if noticed and caught early, good tree care techniques can be applied that may restore the tree to heath. In cases of severe rot and decay, having the tree examined may prevent structural failure of a tree exhibiting crown dieback.
If you have a tree on your property that is exhibiting crown dieback, it is a good idea to have the tree examined by a professional to determine the extent and nature of the issue. Key signs of dieback are bare branch tips and dying foliage during spring and summer. It is natural to have some dead wood in a tree, but extensive dead wood around the entire perimeter of the crown is a cause of concern. With good diagnosis, the proper tree care techniques can be applied to help a tree recover. Waiting and hoping a tree with crown dieback will recover on its own is not a good course of action. Recognizing crown dieback and taking early action is the key to success. Contacting a Certified Arborist (www.treesaregood.org ) is a good step in getting an opinion on the extent of dieback, if the tree is recoverable, and how to best address the issue. You can also contact your local County Extension Office or Florida Forest Service County Forester for assistance.
Recently, I spent some time with my uncle at his home in Perry, Florida. Perry specifically and Taylor County as a whole were one of the hardest-hit areas from Hurricane Idalia. My uncle said that most of the powerline poles had been replaced in his and surrounding neighborhoods as a result of this storm. Some were still being replaced when I was there. Every home in the area had large amounts of tree debris cut and piled up along the streets for pickup. Most every pile had the remains of large pine trunks intermingled in the debris.
Tree debris along street following Hurricane Idalia in Perry, Credit Larry Williams
The only damage to my uncle’s home was from a neighbor’s large pine tree. The top of that tree was blown through the air and slammed into his roof, puncturing the roof and leaving a large hole through the bottom of the garage ceiling. In addition to the direct wind damage and resulting downed trees, with a storm such as Idalia, there will be much follow up removal and pruning of leaning, partly uprooted, and damaged trees.
Trees are an important part of our ecosystem, economy, landscape and heritage here in North Florida. As a matter of fact, Taylor County began a Pine Tree Festival in 1955 to help educate the public about the timber industry in that area. Now known as the Florida Forest Festival, the goal of the festival is to promote the benefits of our state’s forests as well as to celebrate people who protect and work in them. The 68th Annual Florida Forest Festival is scheduled to take place in Perry on October 28, 2023. Here is a link with more information on the festival: https://floridaforestfestival.org.
It is important to not wait until a storm event such as Idalia to inspect and manage trees on your property. An ounce of prevention is worth a pound of cure when preventing tree damage. Even without a major storm, we have relatively high winds associated with our frequent thunderstorms here in Florida. Compared to many parts of the United States, we live in a fairly high-risk area for storm damage with lots of large trees.
Professional help sometimes is your best option when dealing with trees. Property damage could be reduced by having a professional arborist evaluate unhealthy, injured or questionable trees to assess risk and treat problems.
Hiring a certified arborist can be a worthwhile investment. To find a certified arborist in your area, contact the International Society of Arboriculture at 888-472-8733 or at www.isa-arbor.com. In addition, here is a UF/IFAS Extension link with a wealth of information related to trees and hurricanes: https://hort.ifas.ufl.edu/treesandhurricanes.
Tree with dead “hangers” from recent windstorms in the Panhandle. These dead broken limbs should be assessed and removed accordingly. Photo Credit: Ian Stone
Recently our area has experienced multiple severe wind events. You may have noticed some light to moderate damage to some of the trees in your yard. You may have even experienced severe damage or a complete failure of a tree on your or a neighbor’s property. While a complete failure or severe damage pose obvious hazards and need removal, it is the more minor to moderate damage that often raises questions on how to address the issue. Hanging broken branches are often called “Hangers” in forestry or tree care circles. These are often smaller to mid-sized branches which have partially broken off but are still lodged in the tree. After several weeks to a month the foliage starts to die and turn brown, and these “hangers” become obvious in trees that received damage. How do you assess these and when should you get a professional involved? Do they pose a potential health issue if not removed?
These broken limbs are becoming quite noticeable as they die and turn brown. It is important to make good decisions on how to handle these hanging dead branches and how to maintain your tree. Often these hangers are more unsightly than anything else, especially if they are small. Larger ones may pose a risk of damage or injury if they are located over a structure or may fall in an area frequented by people. Most of these hangers will break and dislodge over time, especially in wind events. You should consider the risk posed by the hanging limb, the difficulty and cost of addressing it, and the risk posed by the limb falling. For trees that got noticeable damage with several larger limbs broken, having some repair and rejuvenation pruning done is often good for tree health. You may be able to address some issues yourself if you are handy with a pole pruner and the broken limb is in reach. Anyone attempting even light tree work should be aware of risks posed by falling limbs and use of pole saws. Remember to never attempt to climb trees yourself or perform tree trimming from a ladder or height, as this is fundamentally unsafe. Even limbs which may be safely reached from the ground with a pole pruner can pose risks of injury. If you are attempting to remove some of these hangers with a pole pruner, be very cautious and use good safety techniques. You need to make sure the branch has a landing zone, and you are well clear of it when using a pole saw or pruner. Be aware of vines and other entanglements, and do not work around or within the right of way of electrical or other lines. Larger limbs and those not reachable from the ground should be considered outside the scope of homeowners and left to professionals.
Here is a quick reference guide for how to size up any broken or damaged limbs in your tree and address the situation
Small branches and branch tips with a diameter of the broken branch is 1 inch or less and the branch is hanging or lodged. These size hangers pose little risk and are mostly unsightly. They should fall out of the tree on their own over time. These may be trimmed out slightly behind the break of those within reach of a pole pruner.
Small to Medium branches-1-3 inches in diameter. The branch has partially broken or has completely broken and is lodged in another branch. Branches this size can do some light to moderate damage if they fall on a roof, fence, or other structure. If the branch overhangs areas where people or pets frequent it could cause injuries if it fails. If the branch does not pose a hazard or danger it should dislodge on its own over time. Consider removing these if they pose a risk. They can be removed from the ground with a pole pruner or pole saw but be very cautious as branches this size can easily injure someone that is in the fall zone. Consult a professional if a lift or climbing is required.
Large Canopy Branches 3 inches and larger. These are significant branches and can hold a significant amount of weight. If they are partially broken, hung, or lodged in the tree they may come out at any time and do significant damage or cause injury. These branches are beyond the tools and scope of homeowners, and the damage may require some recovery pruning to keep the tree healthy. Consult with a professional and consider having the damage removed and tree properly trimmed.
Main Branch and Trunk Failures- This is significant damage to the tree which can make it unsound or susceptible to disease in the future. If large main branches have failed, the top has completely failed, or part of the trunk has cracked or split from the damage; major damage has occurred and the tree may not recover. If your tree has suffered this level of damage consult a professional with a tree service and have a certified arborist examine the tree.
It can be hard to tell from the ground what level of damage a tree sustained until the brown foliage appears past the break. Once you can identify what type of damage occurred you can better determine what action is needed. For small branches it may be best just to wait for them to come out naturally or prune them out if this can be done safely with a pole pruner. For larger branches or more severe damage a professional is the best bet. For those hangers that pose a risk to structures or people in an area removal is best, as these could fall at any time and cause damage or injury. Remember never to attempt tree work yourself especially if it involves climbing or working from heights. You can find a certified arborist at www.treesaregood.org to address large limbs and significant damage. A good arborist can help you rehabilitate a tree that has had only moderate damage from a storm. If you are unsure of where to start with a tree that has wind damage, consult your local extension office for some advice.
Use frost cloth to completely cover cold sensitive plants. Be sure to make complete contact with the ground and use heavy objects to keep the fabric secure. Photo by Jonathan Burns.
One major aspect that separates North Florida from South Florida is the discrepancies in air temperature. Although the differences are relatively small when comparing Florida with northern states, they can mean a world of difference in the plant world.
Even hardy cauliflower leaves can be damaged by cold winter nights in the Florida Panhandle. Photo by Molly Jameson.
In most of North Florida, our USDA plant hardiness zone is 8b, which means average minimum winter temperatures are between 15 and 20° Fahrenheit (F). We therefore can experience hard freezes, which happens when temperatures are below 28°F for over five hours. These types of conditions are capable of “burning” the leaves of even the toughest winter vegetables.
Fortunately for our winter gardens, average minimum winter temperatures are in the lower 40s, high enough not to damage winter garden crops. When we do have lows close to or below freezing (32°F), there is one very cost-effective method that can help keep crops and landscape plants protected. This is the use of a material called frost cloth.
Frost cloth can moderate air temperatures six to eight degrees. Photo by Turkey Hill Farm.
Frost cloth, which can be purchased at most plant nurseries, is a breathable polyester fabric that is light weight and heat retentive. When used correctly, it can moderate air temperatures about six to eight degrees. This is typically all that is needed to get us through our mild North Florida winters. It is also relatively inexpensive, and if cared for, the same cloth can be used for many winter seasons.
Large blankets or bedsheets can be used as frost cloth substitutes, but whether you are using actual frost cloth, or something pulled from the linen closet, it is very important to use it correctly to be effective. The cloth must touch the ground at all points, as it works by trapping heat that radiates from the soil. It also increases the humidity around the plant, aiding in temperature moderation.
“Lollipop” trees will allow the heat from the ground to escape, giving the tree no cold protection. Photo by Jonathan Burns.
For sensitive landscape plants and fruit trees, it can be more difficult to fully cover the plant with the frost cloth to trap the heat, but it is just as important. When driving around town on a cold night, I inevitably encounter a few “lollipop” trees. This is when the foliage of the tree is wrapped in frost cloth, but the cloth does not reach the ground, and is typically tied off at the upper trunk of the tree. All heat moving upward from the soil will go right around the cloth, giving the tree essentially no protection.
Wire or PVC hoops can be used to help secure frost cloth and keep the cloth from damaging sensitive plant stems and leaves. Bricks, sticks, soil, or garden staples should be used along the perimeter of the frost cloth to prevent nighttime gusts from blowing the cloth off your garden beds or landscape plants. In the morning, remove the cloth once air temperatures reach about 50 to 60°F.
Over the last decade or so, the Panhandle has been overrun, and I don’t just mean by the summer beach traffic. Rather, by an aggressive, exotic perennial grass that quickly displaces all native species, is not useful as a forage to wildlife or livestock, can spread by roots or seeds, and has no natural enemies. If you own property in the Panhandle or spend any amount of time on its roads, chances are you have become acquainted with this worst of invasive species, Cogongrass (Imperata cylindrica).
A native of Southeast Asia, cogongrass was introduced into the US in 1912 around Mobile, AL as a hitchhiker in orange crate packing. Then the 1920s, 30s, and 40s, it was intentionally introduced from the Philippines into other Gulf Coast states, including Florida, as a potential pasture forage for livestock. Since then, cogongrass has become one of the most economically and ecologically important invasive species in the US and worldwide, infesting nearly 500 million acres and is now found on every continent.
Cogongrass in Calhoun County, FL. Photo courtesy of Daniel Leonard.
Cogongrass is easily identified in late spring, when the grass throws easily spotted fluffy, white-colored seedheads above the mats of grass beneath. Additionally, patches of cogongrass are almost always noticeably circular in nature, radiating out indefinitely from the initial infestation. A closer inspection of the grass will reveal light green leaves up to 4’ in length, with an off-center, silvery colored midrib (the primary leaf vein that runs from the base of the leaf to the tip) and serrated leaf edges. Underground, cogongrass exhibits a dense underground root system that can reach as deep as 4’. This feature is the primary reason cogongrass outcompetes other plants, withstands any drought, fire, or soil condition thrown at it, aids in its resistance to herbicide activity, and generally makes it very difficult to manage.
The first step in managing cogongrass is prevention. If your property or the property you manage doesn’t have cogongrass, do everything you can to keep it that way. While the species can spread distances through seed dispersal, it is much more frequently moved around by fragmented rhizomes hitching a ride on equipment. If you or a contractor you’ve hired are working in or around an area with cogongrass present, avoid disturbing it with equipment and be diligent in monitoring the site for outbreaks following the job’s completion.
If you find cogongrass on your property, effectively eradicating it requires patience, persistence, and several years’ worth of herbicide applications. Currently, of the hundreds of herbicides available for purchase, only two chemistries have been proven to be very effective in destroying cogongrass, impazapyr (Arsenal, Stalker, etc.) and glyphosate (Roundup, Cornerstone, etc.).
Imazapyr is an extremely effective non-selective, residual herbicide that controls a wide variety of weed species, including cogongrass. Just one or two applications of imazapyr can provide 18-24 months of effective cogongrass control, with follow up treatments required as needed after that. However, Imazapyr has a major downside that limits its use in many settings. Because it is a non-selective herbicide with significant soil residual activity, it cannot be used around the root zones of desirable plants. Oaks, other hardwood trees, and most landscape plants are especially sensitive to imazapyr. This herbicide is best limited to use in fields, waste/fallow areas, natural areas, and monoculture pine plantations – it is not appropriate in most residential and commercial landscapes.
The other option, glyphosate is a non-selective herbicide with no soil residual activity. It is often a better option where severe injury or death of desirable hardwood trees and ornamental plants cannot be tolerated. However, due to its lack of residual soil activity, glyphosate applications on cogongrass patches will need to be repeated on an annual or biannual basis for up to five years for eradication of the infestation.
*Regardless of which herbicide you choose, controlling cogongrass is a multi-year affair requiring diligence and patience.
For more information on cogongrass and for specific herbicide recommendations and application rates/timing for your site, please contact your local UF/IFAS County Extension Office.
Hot, summer months are not the time to be using most lawn herbicides.
One issue is the heat of summer. Most lawn herbicide labels include statements such as the following.
“Do not apply when temperature exceeds 90°F.” “Do not broadcast apply this product when air temperatures are above 90°F (85°F for St. Augustinegrass) unless temporary turf injury can be tolerated.”
Every year we’ll see lawns that are injured or killed because of lawn herbicides being applied when temperatures are too hot.
Summer is usually a rainy and windy time of the year. Many lawn herbicide labels include statements such as the following.
“Allow 12 hours after application before watering lawn for maximum effectives on listed weeds.” “Apply only when wind is no more than 10 mph.” “Applying this product in calm weather when rain is not predicted for the next 24 hours will help to ensure that wind or rain does not blow or wash pesticide off the treatment area.”
It is critical to read and follow the label directions and precautions for any pesticide you use. Pesticide labels, including herbicides, include the following statements.
“To the extent consistent with applicable law, the buyer assumes all risks of use, storage, or handling of this product not in accordance with label directions.” “It is a violation of Federal law to use this product in a manner inconsistent with its labeling.”
Crabgrass growing in centipedegrass lawn. Photo credit: UF/IFAS Extension
By the time summer arrives, many of the lawn weeds are mature, which means they are well established with extensive root systems. These mature, well established weeds are much more difficult to control. They are more susceptible to herbicides when they are small, young, and not well established. Also, these mature weeds have been allowed to produce countless numbers of seeds as they move into summer. Most weeds are prolific seed producers. For example, a single crabgrass plant (a common summer lawn weed) can produce 150,000 seeds.
Applying a preemergence lawn herbicide in February to help prevent summer annual weeds such as crabgrass or applying a postemergence lawn herbicide during spring while the weather is mild and before the weeds are out of control simply makes more sense than waiting until summer.
The best options now with lawn weed control involve continuing to follow good mowing practices, maybe hand removal of some weeds, and just simply waiting it out until next February and spring to worry with the use of lawn herbicides.
In the meantime, you may want to read the following UF/IFAS Extension publication on lawn weed control.
