We gardeners in the Panhandle have been spoiled by several very mild winters recently. However, it appears that this pattern will change, at least for a few days, beginning Thursday night. While forecasts vary depending upon your preferred media outlet, all agree that Calhoun County is going to experience several freezing nights (temperatures in the low 20’s to high teens for hours at a time). That’s plenty cold to kill many cold-sensitive plants, so here are a few tips to keep your treasured plants alive until warmer conditions arrive next week.
Covering plants to protect from frost, cold snap, blanketing, potted plants, horticulture. UF/IFAS Photo: Sally Lanigan.
Bring cold-sensitive potted plants inside. You can’t dig up your citrus trees and bring them in the living room but bringing cold-sensitive potted plants inside for a couple of nights is a fail-proof freeze protection method.
Water outside plants the day before extreme cold hits. It’s natural, even good, for many tender plants (perennials, bulbs, etc.) to “die” back in cold weather. This encourages dormancy and reduces pest/disease populations. However, this week could get cold enough to kill “tops” of sensitive plants AND freeze root systems. To help prevent this, water the day before a freeze as moist soil loses heat less rapidly than dry. A few degrees can make all the difference!
Apply mulch around the base of plants. Mulch helps insulate the soil and reduces radiant heat losses. For plants with a graft – like most citrus, pile mulch up around the grafted area. If the top of the plant dies back, at least it will be able to recover from above the graft (the desirable part of a grafted plant).
Cover citrus and other plants that recover slowly from cold damage. Draping a non-plastic cloth or blanket mostly helps keep frost off and freezing wind off plants but can also insulate from freezing temperatures if it covers the entire plant to the ground. It’s better than nothing.
Build a “greenhouse” around plants. You can create a simple greenhouse structure of wooden stakes, pipe, or posts and cover with plastic (making sure the plastic doesn’t touch leaf or stem tissue). Be sure to get this structure up while the sun is still shining before the freeze event to capture as much solar heat as possible. For even better results, install a lightbulb, non-LED Christmas lights, or some other heat source inside the plastic structure.
Last ditch method –turn on the sprinkler. Continuouslyrunning a sprinkler over sensitive plants can help protect them. By running water, you “insulate” the plant to the water’s temperature (above 32 F). This method requires that the sprinkler begin running before the thermometer drops below 32 degrees and must continue uninterrupted until after the freeze event is over. If you stop before the freeze is over, the water left on the plant will freeze to whatever temperature the air is, injuring or killing the plant.
We don’t have many freeze events so take a little time this week to bring sensitive plants indoors and implement one or more of the above precautionary measures in your landscape! Don’t let a few hours of very cold weather set your plants back years! For more information about cold protection in the lawn and garden, contact your local UF/IFAS County Extension Office. Stay warm and Merry Christmas!
Bananas are a great choice for your landscape, whether as an edible fruit producer or simply as an ornamental, giving your space a tropical vibe.
Bananas are native to southeast Asia, however, grow well across Florida. Complementary plants that can be paired with bananas in the landscape are bird of paradise (banana relative), canna lily, cone ginger, philodendron, coontie, and palmetto palm, just to name some.
Bananas are very easy to manage during the warmer months. Bananas are water loving, and that’s putting it lightly. Planting in vicinity of an eave on your home is a good measure for site suitability. Roof rainwater will drastically increase the growth of the banana tree and decrease the need for supplemental irrigation. Banana trees will need full sun and high organic moist soils create the best environment. For nutrition, a seasonal one-pound application of 6-2-12 fertilizer is a good practice to sustain older trees. Young trees should be fertilized every two months for the first year at a rate of a half-pound.
Musa basjoo is one of the most cold hardy banana varieties. Photo Credit: University of Florida/IFAS Extension
If there is a con to banana trees, it’s their cold hardiness. Some varieties fair well and others some not so much. ‘Dwarf Cavendish’ (Musa acuminate) is a popular variety that is found in many garden centers in the state. It produces fruit very well, but it is not very cold hardy. ‘Pink Velvet’ (Musa velutina) produces fruit with a bright pink peel, but isn’t very cold hardy either. A couple of cold hardy ornamental varieties are the ‘Japanese Fiber’ (Musa basjoo) and ‘Black Thai’ (Musa balbisiana), which is by far the most cold hardy, with the ability to easily combat below freezing temperatures.
Freeze damage on a banana tree. Photo Credit: Ray Bodrey, University of Florida Extension – Gulf County
Regardless of cold hardiness, in many cases, banana trees will turn brown after freezing temperatures occur or even if the temperatures reach just above the freezing mark, but will bounce back in the spring. Until then, it’s important not to prune away the brown leaves or trunk skin. These leaves act as an insulator and help defend against freezing temperatures. Usually, the last freezing temperatures that may occur in the Panhandle are around the first of April. So, to be safe, pruning can begin by mid to late April. When pruning, be sure to be equipped with a sharp knife, gloves and work clothes. Banana trunk skin and leaves can be quite fibrous and the liquid from the tree can stain clothing and hands.
So, what’s the best variety of fruiting bananas? Most ornamental bananas do not produce tasty fruit. If you are looking for a production banana, ‘Lady Finger’, ‘Apple’, and ‘Ice Cream’ are popular varieties, but are better suited for the central and southern parts of the state.
For more information, contact your local county extension office.
Frost on Dune Sunflower Picture by: Pam Brown UF/IFAS Extension
December is finally here and that means consistent nights of watching for dropping temperatures. Tropical plants and newly installed shrubs are susceptible to cold injury. Those colorful, blooming plants that have added a tropical look to the landscape all summer may begin to suffer when the temperatures drop below 500 F. Leaves may turn yellow and flowering stops. These plants will need to be moved inside or have temporary greenhouse built around them. But, hardy plants that haven’t established a sufficient root system will also need additional attention when the temperatures drop dramatically.
The ability of plants to endure a freeze depends on the species and the weather leading up to the extra cold night. Gradual decreases in temperatures helps plants acclimate to winter. But, a sudden one day drop of 40-50 degrees results in a rapid freeze that causes ice to form inside the plant cells. Leaf and stem tissue expands so quickly that it splits, resulting in parts of the plant incapable of transporting water and nutrients, as well as, performing photosynthesis. However, it may be late the following spring before the damage is noticed, when that section of the plant has slowly staved to death.
Cracked bark from frost
Additionally, plants can experience desiccation or drying out. This happens when dry winds and solar radiation result in the loss of more water from the leaves than can be transported by a cold root system. The resulting symptom is marginal and/or tip burning of leaves that leads to totally brown leaves.
Freezes (when the temperature drops to 320 F) are characterized as radiational or advective. Radiational freezes occur on calm, clear nights when heat radiates from the surfaces of plants, making them colder than the air due to the rapid loss of heat. If there is moisture in the air, ice will also form on the surfaces. Under these conditions, ice forms between plant cells, rather than within the individual cells. Most hardy plants can tolerate these type of freezes if they are properly hydrated.
Advective freezes occur when cold northern winds move in rapidly, dropping temperatures quickly, and causing widespread foliage desiccation. Cultivation and maintenance practices can impact a plant’s ability to endure extended periods of low temperatures. Shade-tolerant species installed under the canopy of a tree typically display less injury from radiational freezes because the trapped heat from the ground and the overhead foliage creates a microclimate. Well-watered soil around a plant will absorb solar radiation during the day and re-radiate heat over night, raising the temperature around the plants. Shrubs that are not pruned in the late summer or fall have leaves that can withstand frost and wind. But, the removal of foliage late in the growing season triggers a flush of new growth, that is very sensitive to lower temperatures. The same response can result from fertilizer applications after plant’s have slowed down in growth.
Irrigation Frost Protection on Citrus
Row Cover Picture by: Univ of Maryland Extension
So, what can you do to prepare for upcoming freezing temperatures? Begin by avoiding pruning and fertilizing at the end of the season and making sure that the plants have been watered within 24 hours of a cold night. Next, insulate against water loss and increase heat radiation by adding a three-inch of mulch, as well as, covering the trunks of sensitive trees with a commercial tree wrap. Then, consider what needs to be covered. Frost cloth or other breathable fabrics can trap heat for the night and provide a protective layer from frost settling on the leaves. It needs to be placed by mid-afternoon and removed the next day when temperatures are above 320 F. Plastic is not recommended unless the timing regime can be followed reliably and a structure is used under the material to keep the plastic off the foliage. Anchoring of the cover is critically important in the event of an advective freeze.
Finally, turn off the sprinkler system. Commercial agriculture often uses a running irrigation system to keep the leaf surface temperatures near, but not below, 320 F because sprinkling utilizes latent heat released when water changes from a liquid to a solid state. The thin layer of ice melts and re-freezes on the surface throughout the night, without ice forming within the plant tissues. For the technique to work, sprinkling must begin as freezing temperatures are reached and continue until thawing is complete. Landscape systems are not designed to deliver the amount of water over the length of time required to accomplish this type of frost protection.
When the cold nights have passed, don’t forget to check your plants for water. But, wait until winter has passed before pruning out the frost damaged stems.
Spring is a wonderful time of year. After months of dreariness and bare branches, bright, succulent green leaves and flowers of every kind and color have emerged. So too, have emerged gardeners and outdoor enthusiasts ready to tackle all their home and landscape improvement projects planned over the winter. However, this is also the time, when folks first start paying attention to their plants again, that strange, seemingly inexpiable plant problems crop up!
All plant problems can be divided into two categories: biotic problems, or issues caused by a living organism (think insects, fungus, and bacteria), and abiotic problems, issues that arise from things other than biotic pests. It’s the first category that people generally turn to when something goes wrong in their landscape or garden. It’s convenient to blame problems on pests and it’s very satisfying to go to the local home improvement store, buy a bottle of something and spray the problem into submission. But, in many of my consultations with clientele each spring, I find myself having to step back, consider holistically the circumstances causing the issue to arise, scout for pests and diseases, and if I find no evidence of either, encouraging the person to consider the possibility the problem is abiotic and to adopt patience and allow the problem to correct itself. Of course, this is never what anyone wants to hear. We always want a solvable problem with a simple cause and solution. But life isn’t always that easy and sometimes we must accept that we (nor a pest/disease) did anything wrong to cause the issue and, in some cases, that we ourselves actually caused the problem to happen in the first place! To illustrate, let’s consider two case studies from site visits I’ve had this spring.
Cold damage on Boxwood hedge
Three weeks ago, I got a call from a very concerned client. She had gotten her March issue of a popular outdoor magazine in the mail, in which was a feature on an emerging pathogen, Boxwood Blight, a nasty fungus decimating Boxwood populations in states north of us. She had also noticed the Boxwoods in front of her house had recently developed browning of their new spring shoots across most the hedgerow. Having read the article and matching the symptoms she’d noticed to the ones described in the magazine article, she was convinced her shrub was infected with blight and wanted to know if there was a cure. Agreeing that the symptoms sounded similar and wanting to rule out an infection of an extremely serious pathogen, I decided to go take a look. Upon inspection, it was obvious that Boxwood Blight wasn’t to blame. Damage from disease generally isn’t quite as uniform as what I saw. The new growth on top of the hedge was indeed brown but only where the eaves of the house and a nearby tree didn’t provide overhead cover and, to boot, the sides of the hedge were a very normal bright green. Having gone through a recent cold snap that brought several mornings of heavy frost and knowing that the weeks before that the weather had been unseasonably warm, causing many plants to begin growing prematurely, all signs pointed toward an abiotic problem, cold/frost damage that would clear up as soon as the plant put on another flush of growth. The client was delighted to hear she didn’t have a hedge killing problem that would require either adopting a monthly fungicide regime or replacing the hedge with a different species.
Damage to ‘Sunshine’ Ligustrum from pressure washing siding with bleach.
The very next week, another client asked if I would come by her house and take a look at a hedge of ‘Sunshine’ Ligustrum that lines her driveway, whose leaves had “bleached” out, turning from their normal chartreuse to a bronzy white color. This time, having seen similar issues with this particular plant that almost always involved an infestation of Spider or Broad Mites, I figured this was a cut and dry case that would end with a call to her pest control company to come spray the offending bugs. However, though the leaf damage looked similar, I was not able to locate any existing pests or find evidence any had been around recently, rather it appeared the leaves had been exposed to something that “bleached” and burned them. Puzzled, I began asking questions. What kind of maintenance occurs on the plants? Have you fertilized or applied any chemicals recently? Nothing. Then, near the end of our conversation, the client mentioned that her neighbor had pressure washed their house on a windy day and that she was irritated because some of the soap solution had gotten on her car. Bingo. Leaf burn from pressure washing solution chemicals. This time I was guilty of assuming the worst from a pest when the problem quite literally blew in on the wind from next door. Again, the client was relieved to know the plant would recover as soon as a new flush of growth emerged and hid the burned older leaves!
This spring, I’d encourage you to learn from the above situations and the next time you notice an issue on plants in your yard, before you reach for the pesticides, take a step back and think about what the damage looks like, thoroughly inspect the plants for possible insects or disease, and if you don’t find any, consider the possibility that the problem was abiotic in nature! And remember, if you need any assistance with identification of a landscape problem and want research-based recommendations on how to manage the problem, contact your local UF/IFAS Extension office.
Photo Caption: Unused tomato cages are a perfect support for heavy covers which can protect delicate landscape shrubs during the frosts of winter. When spring arrives, they can again be used to support tomato plants. Image Credit Les Harrison
The Thanksgiving turkey is but a distant memory, the stores are stocking for the spring, and Christmas decorations are coming down.
The advent of the new year, finally brings the inevitability of cold and frosty weather. While nothing complements a nice eggnog or hot chocolate like a chill in the air, some northwest Florida landscape plants do not appreciate the dropping temperatures.
Gardeners face a new set of challenges dealing with the effects of cold weather. However, a little planning and creativity can make plant protection in the landscape a relatively simple process.
Many homeowners and landscape managers want to know when plants will need protection. Depending on the plant, the point of freezing is a good rule of thumb. Freezes will likely occur this season so preparations should begin now.
It is worth noting there is a difference in the terms used for cold weather conditions. Frost, freeze and hard freeze all describe different circumstances.
Frost is when water vapour freezes on surfaces. It usually happens on clear nights with still air and can happen when reported air temperatures are above freezing.
Freezing is when cold air moves in and causes temperatures to drop below 32 degrees Fahrenheit. This condition commonly involves low humidity and wind, making drying out a big problem for plants.
A hard freeze is when temperatures dip below 28 degrees Fahrenheit. Some tropical plants will survive a few degrees below freezing for very short periods, but extended periods of freezing or heavy frost may require lights or other heat used safely in combination with covering the plant.
In the Panhandle, most of the risk for sustaining freeze damage happens during the busy holiday season. People are busy, schedules are disrupted and the distractions, pleasant thought they be, may cause homeowners to miss a critical freeze alert in the media.
Some plants can be moved indoors for the cold months and incorporated into the interior décor, rather than cramming them last-minute into a chaotic bundle when a freeze looms.
While putting away the holiday decorations into storage, identify old sheets, blankets and drop cloths which can be used as covers for tender plants which must remain outside. Test potential covers beforehand to assure all plants will be thoroughly covered.
It is best if the covers enclose the plant entirely without crushing it. Heavy blankets are great insulation, but only a good idea on the sturdiest of plants.
A tomato cage or other support structure can be used to keep the weight off the plant. Covers also need to be secured at the ground with pins or weights to assure cold air does not enter from below and collect under the cover.
Finally, keep storage bins handy and remove the covers in the daytime if temperatures are above 55 degrees Fahrenheit.
Monitor weather reports and react accordingly so your tender and tropical plants see spring 2018. Santa will approve.
