The Borneo camphor tree (Dryobalanops aromatica) exhibits a perfect example of crown shyness. Photo from Wikimedia commons at the Kuala Lumpur Research Forest
I spent a lot of time in my childhood lying in our backyard hammock, reading. Inevitably, I’d take a break and stare up at the tree canopy above me. We had sweetgum trees in that corner of our yard, and I’d watch squirrels chasing each other through the branches. One thing I noticed, but never really investigated, was how the highest branches spread out towards each other from the clump of trees, yet didn’t touch or overlap each other. You could nearly always see gaps of sunlight outlining the individual trees.
The canopy of mature oak trees exhibiting crown shyness. Photo credit: Carrie Stevenson, UF IFAS Extension
The term for this is “crown shyness.” As anthropomorphized as that seems, it’s an apt description for this seemingly polite growth pattern. The topmost branches of any given tree are in constant competition with each other for sunlight. Being photosynthesizers, sunlight is life. No growth can happen without the basic ingredients of sunlight, water, and carbon dioxide. So, from a tree’s perspective, there is an inherent disincentive to send growth beneath their own existing branches or those of an adjacent tree. The result of this is a botanical dance of sending branches out, neighboring trees doing the same, and multiple trees subtly angling for light. It’s like sharing an armrest on an airplane with a stranger. There’s a limited and highly desirable resource (the armrest), resulting in a (hopefully) gentle back and forth where someone either claims the space fully or you make an unspoken agreement to share it. If you do share it, it’s rare your arms touch; most of us want to keep some personal space!
Like Blue Angel jets in the diamond formation, trees will keep just a bit of sunlight between them and their neighbor. Photographed by Mass Communication Specialist 1st Class Ian Cotter. Official U.S. Navy Photograph.
While we may consciously shuffle for position in crowded public spaces, this happens for trees at a metabolic level. Evidence from an Argentinian study demonstrated that trees can “detect the presence of neighbors before being shaded by them,” using an internal sensor that detects light on the red:far red spectrum. This botanical spidey-sense comes from light-receptor proteins called phytochromes, which send out an alert that they’re close to another tree and may want to stop sending branches that direction. Growing into an adjacent tree quickly brings diminishing returns for absorbing sunlight, and it is in the tree’s best interest to keep a safe distance.
Single-species stands of pine trees exhibit crown shyness. Photo credit: Tyler Jones, UF IFAS
Crown shyness appears to be more pronounced in groves of same-species trees. Monocultures like pine plantations, or even large stands of black mangrove, exhibit the same growth patterns and timing, adapting to environmental factors the same way—particularly if they were planted or germinated at the same time. Foresters or ecologists trying to maximize the space for timber, fruit, or ecosystem restoration may want to deliberately encourage a diverse array of species, which fill in the gaps beneath the canopy and survive on less direct sunlight.
Maybe we could call it “crowd” shyness when people step back to give folks room to dance, avoiding “mechanical abrasion”! Photo credit: Cole Stevenson, University of the South
Another contributing factor to crown shyness, and perhaps one of the more crucial ones, is “mechanical abrasion.” University of Florida botanist Francis “Jack” Putz conducted research on this in Costa Rica back in the 80’s, which is still frequently cited in more recent publications. His team’s findings showed that crown shyness was “positively correlated with the distance pairs of trees adjacent to the gap swayed in the wind.” When tree branches physically bumped into one another on a regular basis, they kept their distance to prevent bud, bloom, and branch tip damage. For this scenario, imagine someone dancing enthusiastically in the middle of a big music festival—if there’s room, people will often spread out. The more the person flails, the more space you give them. If they’re just minimally swaying back and forth, you might stand closer. Putz, et. al observed this same principle in the coastal mangrove forests—more flexible branches adjacent to one another gave each other more space, while those with “stiff crowns” that couldn’t move much grew closer together.
When space opens up due to the loss of a neighboring tree or branch, the infusion of sunlight/fuel spurs a tree to send energy quickly to gain the advantage over adjacent trees. Tree species vary in their capability and success in doing this. An earlier article on pioneer species (the first to occupy a newly open space) and the process of succession sheds more light on this natural phenomenon. In a mature forest, the end result is a balanced mosaic of tree branches reaching out and nearly touching one another, but leaving each other space to grow.
Pine Bark Beetles are an ever-present issue in both the urban and rural landscape across the Panhandle. If you have pines in your landscape you very well may experience issues with pine bark beetles. The tiny insects can decimate a pine rather quickly, and there are more than one type that can infest a tree. The Southern Pine Beetle is the bark beetle that most people are familiar with and most concerned about. In forestry settings the Southern Pine Beetle can have epidemic outbreaks that can devastate large areas of pine forests and plantation. While the Southern Pine Beetle is very destructive and a concern to forest health, there are other common pine bark beetles that often attack trees in our area. The two other common bark beetles are Ips pine engraver beetles and Black Turpentine Beetles. In urban settings these two beetles often are more common but they can easily wipe out several trees or more, which may pose a significant issue in the landscape.
Resin pitches on bark that indicate pine bark beetle infestation. This shows a pine that is actively colonized by bark beetles and should be removed. Photo Credit-Ian Stone
There are multiple species of Ips beetles and these tend to be a significant issue in landscapes, because they can easily wipe out most of the trees in a yard or park. They almost always target stressed or damaged trees, but they usually do not wipe out large areas like Southern Pine Beetle. Different Ips species will often attack different portions of the tree which can result in partial dieback of the crown or a slow yellowing and browning of the foliage. These beetles are very small, smaller than a grain of rice, and often are not seen readily without close inspection. Like other bark beetles the bark will often have resin oozing out and forming small pockets resembling popcorn. Other signs include yellowing and browning foliage and an accumulation of sawdust like material around the base. You may also see exit holes in the bark about the size of a pencil lead.
The Black Turpentine Beetle is closely related to the Southern Pine Beetle, but much larger and often attacks the lower portion of the tree. These beetles commonly attack older, damaged, and weakened trees. Historically they were often associated with turpentining operations and trees that had been worked for resin production, hence their common name. They are very attracted to trees that are damaged by equipment or that have had construction occur around them recently. The symptoms are generally the same as other pine bark beetles, but the resin pitches are larger and the exit holes are about the size of an eraser. While they are larger than other bark beetle they are still quite small by comparison to other insects, not much larger than a grain of rice and somewhat smaller than a pea.
If you notice pines in your area with bark beetle symptoms it is natural to be concerned. As the weather warms bark beetle activity increases and you may notice these symptoms on your pines. If you had bark beetles attack a tree in your yard last year you will want to keep an eye out for other pines being attacked in the spring. With the drought last year bark beetle activity increased and if the infected trees were not removed spots may reactivate in the spring and summer. Unfortunately, once bark beetles attack a pine there is really nothing to do other than removal. Insecticides and sprays will not do anything against bark beetles that are already in the tree. If you have high value pines in your landscape you want to preserve, prevention is key. First and foremost avoiding issues from equipment damage and construction is key as this will attract beetles. Preventative injections with systemic insecticides by a licensed professional can protect trees in your landscape. If you have noticed bark beetle activity in the area or have had to recently remove trees that died from bark beetles, consider preventative treatment to preserve trees that are at risk. Otherwise removing trees that become infested with bark beetles promptly is the best solution. Sometimes it can be difficult to determine what trees to remove, but any trees showing active bark beetle activity should be removed to prevent spread. Once bark beetles have colonized a tree and it is in decline preventative insecticide treatments are not going to be effective. You also don’t need to remove every pine in your landscape just because a single tree has bark beetles. At the following link you will find an IFAS EDIS article that is helpful in identifying bark beetles and making a decision about an infected tree https://edis.ifas.ufl.edu/publication/FR399.
If you see bark beetle activity on your property this spring contact your local IFAS extension office or your Florida Forest Service County Forester’s office for assistance and information. A Certified Arborist can assist you with determining how to remove infected trees or apply preventative treatments to trees at risk. With good decision making and management pine bark beetle attacks can be managed before they grow and spread. Now is a good time to keep an eye out and get ahead of any infestations that start.
It has been a hard summer climate wise and as we go into fall it is nice to start getting some relief from the heat. As the heat tones down, we are still facing a drought, which is not as severe as areas to our west but is still significant across much of the Panhandle. In our tree cover, the stress from the harsh summer this year is starting to show. You can see it in trees around the area, and it particularly seems to affect certain trees and conditions more than others. Where you are starting to see it most is in our ever-present pines, which make up the majority of our forest and tree cover in our region. If you keep a look out you may notice some pines in the areas with yellowing or brown needles or that are losing their needles. Those are clear signs of a possible bark beetle attack, which is a common issue when pines are stressed or damaged. Trees planted in the last year that are not yet fully established often show stress in a hot dry summer like this year. Even older and well-established trees in areas are showing some signs of stress from the hot dry conditions we have had this summer. Some trees are less adapted to dryer areas and when planted off site can experience more stress in dry conditions. If you look around across the Panhandle right now you can see clear signs of stress in some trees. It becomes more evident in late summer and early fall as the accumulated stressors of summer push trees into physiological conditions that cause stress responses. The big question is what to do if you notice a landscape tree that is exhibiting signs of stress, particularly drought stress.
Pine damaged by construction equipment. Barking injuries like this can encourage bark beetle attacks. Photo Credit: Ian Stone
For pines the issue is likely to be bark beetles, of which there are several types. All pine bark beetles are native to our area and the degree of damage they do varies by species and conditions. The issue with stressed trees is that most bark beetles attack those trees. When a hot dry summer occurs bark beetle activity increases as the stressed trees become less able to fend off attacks by these beetles. Unfortunately, when bark beetles attack a pine in an area the best answer is prompt removal and disposal of the infected tree material. To protect high value trees in an area where bark beetles are active there are some injection pesticides that can prevent infestation, but once a tree has been infested and begun to show symptoms little can be done to bring it back. When bark beetles attack a stressed pine, most are effectively finishing off a tree that may have died regardless. The key is to prevent them from spreading to other pines in the area or attracting them to a stressed tree in an area. With trees already stressed in our area the big prevention option is not to damage or stress any pines already on the landscape. Most pine bark beetles are attracted to trees by chemicals in pitch and resin given off by wounds or damage. Often the stress from new landscaping projects or construction around pines can cause several to succumb to bark beetles. Your best prevention is to keep equipment well away from the tree and avoid damaging or injuring the tree, especially scraping areas of bark off. Larger and older trees can be vulnerable, as well as overcrowded trees that are too dense or overtopped by others. As the cooler weather approaches bark beetle activity should decrease along with the risk of losing a pine to these pests.
Recently constructed sidewalk. Construction activities extended well into the root zone of the tree, which can cause stress and damage. Photo Credit; Ian Stone
For other trees there are additional precautions that can be taken to lessen the potential that a tree will succumb to drought and other stress. Newly planted trees or those established in the last several years are particularly at risk and should be watered regularly during this dry period. Until rains return, a good method of slowly applying water deeply to the root zone is best. Properly applied mulch can help keep the soil cooler and moist around a newly planted tree. Drip irrigation, soaker hoses, and similar methods are best, and a method that specifically applies water slowly to the tree’s root zone gives the best results. Watering your lawn does not supply sufficient water to landscape trees, especially in drought conditions. Lawn irrigation is designed to apply irrigation needed to the top portion of the soil that is available to the grass. Trees have completely different requirements and need different watering methods and amounts. If you don’t have dedicated irrigation available and you have a tree that needs water, you can use irrigation donuts or bags. These are often a good solution for a tree that needs watering temporarily. Once a tree is well established it usually can withstand even severe drought, but during the establishment phase paying attention to water needs is critical in a summer drought like we have had.
Large established trees are also not immune from the heat and dry conditions that have plagued the Panhandle this summer. Usually when conditions change these trees recover but may abort some branches or exhibit some leaf drop while stressed. Leaf drop is a phenomenon that can occur when deciduous trees are stressed. It is a method of conserving water needs by reducing the leaf demand. Usually, the tree will recover and leaf out again fine next year. A tree may abort some branches or have some branch tips die back to make it through a rough period. Trees that are overcrowded, overtopped, or have other issues are the most at risk from environmental stress. This is why good tree selection along with proper tree care and maintenance is essential. When a hot dry summer like we have had comes along well cared for and maintained trees do best. Trees that prefer more moisture like bald cypress, red maple, sycamore, and some oaks can be planted in dryer sites, but when a severe drought comes along they often don’t have the ability to handle the moisture stress that trees adapted to dryer sites can. This is why site selection is so important, it is when we have extreme conditions that off site plantings typically suffer the worst and those can be larger more established trees.
With the cool weather hopefully we will get a reprieve and some rain soon. Given that fall is one of our dryer periods it may be likely that drought conditions could persist until early winter. Good care and tree maintenance is essential to getting your trees through stressful periods like this summer. For younger trees watering and care is essential while they get established. For older established trees avoid doing any construction or other disturbing activities around them until conditions improve. If you have trees that are exhibiting signs of decline or pest attacks call your local extension office or Florida Forest Service County Forester office. With any luck, colder weather with winter rains will be here soon and trees in our area will recover over the dormant period.
Landscaping in the Panhandle of Florida comes with many opportunities and challenges in this diverse plant environment of coastal, flatwoods (aka pine woodland), sandhills, and clay soil areas running adjacent to the Alabama/Georgia lines. Sandy soil is the predominate soil of the panhandle area from coastal saltwater marshes and brackish bay waters to wetlands and drier well drained quartz sandy soils of the sandhills. Unique ecosystems can be found in all these areas. One of the areas with the largest plant diversity is the Longleaf Pine savannahs found in the sandhills. Now comes the question of landscaping decisions for your residential living.
Native landscape plants. Photo Credit: Stephen Greer, University of Florida/IFAS Extension – Santa Rosa County.
Understanding your soils and how to improve them where you live is critically important before putting the first plant in the ground. We live in an area of abundant rainfall and this will impact the chemistry of your soils. Make an appointment with your local horticulture agent at the University of Florida IFAS Extension office in your county to discuss your soil and landscape ideas. Taking soil samples will likely be needed. With instruction you can easily collect the samples needed to be sent and received to determine the best options.
With abundant rainfall, leaching of key nutrients will occur removing base cations that can include potassium (K), magnesium (Mg), calcium (Ca) and others. This all leads to soils being more acidic in nature. Nutrient resources may need to be added and checked every 2-3 years, just be sure to follow the soil sample recommendations. Soils near wetland areas can leach differently than the deep quartz sandy soils of the sandhills. Adding organic amendments is a recommended practice. Just how much will depend on your soil setting; talk with your horticulture Extension agent. Often new homesites and commercial construction areas have soil brought in to raise or level construction locations. Understanding the movement of water through these newly added layers to the existing soil below will determine drainage and nutrient movement within this site. It can be confusing making decisions about adding soil nutrients, lime, and organic amendments.
Challenges in new soils in landscape. Photo Credit: Stephen Greer, University of Florida/IFAS Extension – Santa Rosa County.
Once all this is settled you can start thinking about how to enjoy this wonderful Panhandle outdoor living opportunity. Creating living spaces comes in many ways from building patios, porches, decks, outdoor kitchens, and strategically places chairs and benches. Talk with your family and others who may enjoy these places with you. Gazebos or barbeque grill areas may be in the plans. Placing these into the landscape takes planning. Draft designs and think of creative solutions for the site. Look at the site elevation changes from high areas to low wetland areas. Will you need “No See Um” screen for the porch to keep out the small insects or install ceiling fans to keep the breeze moving?
There are many questions to be asked. Create a list to be addressed before beginning a project and then determine the cost. Enjoy the adventure!
Trees provide shade, aesthetics, and perspective to the landscape. However, they only serve as burdens if not properly selected and maintained. To help determine what trees do best under certain conditions and to provide information on tree care, this month’s Gardening in the Panhandle LIVE! was all about trees.
Florida maple beginning to exhibit fall color. Photo credit: Larry Williams, University of Florida/IFAS Extension – Okaloosa County
Tree Selection
Some trees grow faster than others. That’s not always a good thing, but if you’re trying to select a tree that grows fast and will provide shade in your yard then you might want to give the following species a try. Click on the links for more information.
A lot of times you’ll read a particular tree species prefers moist, well-drained soil. Some coastal soils are very well drained and require supplemental irrigation after establishment to keep some species alive. One tree that does well in sandy, well-drained soils without supplemental irrigation is the sand live oak. Another tree, that would never win a popularity contest, but does well in sandy soils is the sand pine. This tree has a gnarly growth habit, which would make it an interesting focal point in the landscape. Turkey oaks are another option for dry spots.
There are a lot of fruit tree species that can be grown successfully in the panhandle. The key to good fruit production is selecting trees that are adapted to the average number of chill hours (usually calculated by the number of hours between 34ºF and 45ºF) your yard receives on a yearly basis. Some peaches, plums, and nectarines have been developed for our climate. Citrus such as satsumas and tangerine hybrids grow well in the panhandle, but sometimes require cold protection. Persimmons, loquats, and pears are other fruit trees that grow well.
If you already have mature trees in your yard, then you may be looking for smaller, understory trees to enhance your landscape.
Living this far south, you often have to really seek out trees that change color in the fall. Dogwoods, Florida maples, and blackgum trees all have great fall color. Some of the red oaks also have nice fall color. Two that come to mind are the nuttall oak and the Shumard oak.
Trees can cause a lot of damage if planted too close to sidewalks or buildings. To determine if a tree will fit in a confined space, you will need to consider its mature trunk flare diameter.
Florida is the southern extreme for growing ginko trees. If you decide to plant a ginko tree, make sure to select a male cultivar to avoid stinky, slippery fruit.
To successfully plant a tree, you need to start with a healthy tree. If the tree you purchase was grown in a pot, make sure it isn’t rootbound and doesn’t have encircling roots. You also should inspect the tree’s form, branching structure, and look for the presence of included bark. Please read “Selecting Quality Trees from the Nursery” for more tips on what to look out for when purchasing a healthy tree.
Some trees are more tolerant than others of high winds and flooding. Please read this publication about tree failure from hurricanes to help determine what tree species are better adapted to these weather events.
Santa Rosa County Master Gardener Pruning a Stone Fruit tree at the WFREC. Photo Credit: University of Florida/IFAS Extension
Tree Maintenance
Armillaria is a common fungal pathogen that infects trees from their roots. Other major diseases are more specific to certain species. A more comprehensive list of tree and shrub diseases can be found on the Ask IFAS website.
Tree establishment period depends on a lot of factors. Once a tree is established, it’s roots can be equal to about three times the distance from the trunk to the dripline.
Fallen leaves can help add nutrients back to your yard. Even if you are trying for a manicured lawn, you may want to rake up the leaves and use them elsewhere in the landscape.
Regardless of the species, most fruit trees benefit from a good pruning. Deciduous fruit trees should be pruned to maintain good branch structure and form, while citrus may benefit from a light hedging.
Trees are a wonderful addition to any landscape, but it’s important you select the right tree for the right place. Hopefully this article provided some information to guide you in the right direction.
