While palms may survive, or even thrive, for years in climates cooler than those to which they are native, eventually they may experience temperatures cold enough to cause injury. The January 21st snow and wind chill is likely to take a toll on many of the palms in Northwest Florida. We have experience with this since it also happened in January 2014 and December of 2022. Unfortunately, much of the damage in 2014 was not evident for 18-24 months and we are not out of the window for 2022. Healthy palms can hold on with stored food reserves, but repeated events can continue to weaken them. When cold damage is severe, plant tissues are destroyed and water uptake into the plant may be reduced for years. Many times, it is only the protected bud that will remain alive. These palms can still be saved if the bud remains alive. Winter is not over, even though the temperatures are now creeping higher and higher. So, evaluate what damage you may already have and prepare for any additional, yet to come. Here’s a reminder of what to do.
One of the most common problems associated with freezes is that the freeze-killed lower portion of the spear leaf is degraded by secondary fungi and bacteria that are always present in our natural environment. Palm owners are often anxious to trim off the damaged leaves following a cold weather event. Avoid the temptation to remove these fronds until danger of additional freezes has passed. Even dead leaves provide insulation to the critical bud. As the weather warms, the dead fronds need to be removed from around the bud so that the spear can begin to dry out. Drenching the bud area with a copper fungicide will reduce the secondary microbes. Repeat applications will need to continue as the palm leaves develop. Copper fungicides, unlike other fungicides, are active against bacteria and fungi. Be cautious to not use a copper nutrient spray rather than a fungicide. Delay fertilizer application until new fronds have developed. The best analysis for palms is 8-2-12 + 4Mg. Utilization of proper palm fertilization can improve cold hardiness of palms.
Palm trunk decay appeared 2 years after 2014 freeze.
Palms damaged by cold can still show symptoms six months to three years following a freeze. New leaves in the spring may appear misshapen. Usually, the palm will outgrow the damage. However, sometimes the palm loses its ability to take up water. If there is a sudden collapse of the fronds in the crown during the first hot days, the palm may die. There is nothing that can be done to save the palm.
Planting annuals is a great way to add color and texture to the landscape. Annuals can provide an added visual component to the garden regardless of if they’re planted in the ground or in containers, or even better—both. An annual plant completes its life cycle (growing, flowering, seed set, and death) in a single growing season. Annuals can stay in good health and last longer if they are pruned back when they get leggy and by pinching off any fading flowers (deadheading). To help plan your garden beds and container plantings please click below to enlarge the image of the handy “North Florida Annual Planting Guide”. Please note the suggested planted dates in this guide are based on average monthly temperatures, but every year is different. Some years we may have a late frost around Easter, other years we won’t have a cold front after February.
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.
Crape myrtle trees are often aggressively pruned each winter regardless of the location. Learn three steps from the University of Florida IFAS Escambia Extension to selectively prune your crape myrtles to maintain an attractive tree form in your landscape.
During the summer months, we can’t seem to get away from insects. Whether it’s a fly circling your food, those pesky aphids in your garden, or a mosquito out for blood, they make their presence known. But when winter rolls around and temperatures drop, they seem to disappear. But where do they go?
Unlike humans, insects are exothermic or cold blooded. They cannot regulate their own body temperature and must rely on the heat of the environment. Each insect species has its own developmental threshold, a temperature below which no development takes place. For many insects, that threshold is about 50 degrees Fahrenheit. This means that when temperatures drop below 50 degrees Fahrenheit, consecutively, the insect is not active, and no development is occurring. Typically, the warmer the temperature is (as long as it is above the development threshold), the more insect activity we see.
Insects may also enter a state called diapause, which is similar to hibernation. During diapause, an insect’s metabolism slows dramatically, and the insect stops feeding, growing, or reproducing. This allows the insect to survive through cold winter conditions, conserving energy until temperatures warm up again.
Another insect survival technique during the winter is migration. Many species of insects migrate to warmer climates to escape the cold. A well-known example of this is with the infamous Monarch butterfly migration. Monarchs migrate south to Mexico to overwinter and survive the cold weather. Some other insects migrate in smaller, less noticeable ways such as moving to different micro-climates. For example, beetle grubs may move down deep within the leaf litter to stay warm. Insects like lady beetles may congregate in large numbers inside homes, barns, or buildings during the winter.
Some insect species can produce glycerol, a type of anti-freeze, that prevents their body from freezing even when temperatures drop below freezing.
While many insects seem to disappear during the winter, they’re actually using their time wisely and although, cooler temperatures may slow down their activity, they won’t necessarily change insect populations drastically. Insects are well adapted for survival, and they are here to stay. They’re just enjoying a break until the warmth of spring brings them back!
