by Sheila Dunning | Dec 23, 2014
A frozen perennial plant. Photo credit: Taylor Vandiver UF/IFAS Extension.
When you look out at your landscape nobody has to tell you that winter temperatures in Northwest Florida Afterwards, the temperatures warm up and you feel compelled to do something about it. You just need to “turn your back and slam the door”. “Conceal, don’t feel; don’t let them know”. Cold injury can affect the entire plant or just certain plant or parts such as fruits, flowers, buds, leaves, trunks, stems, or roots. Many plant parts can adapt to tolerate cold. Root systems in the landscape are seldom ‘frozen’ in Florida. “The cold never bothered” them “anyway”. While dead, unsightly leaves may be removed as soon as they turn brown after a freeze, the remaining dry looking stems serve as food storage and should be allowed to remain. If they are removed before the weather is warm enough for the plant to resume growth, the root system may not be enough to support the plant and it will die. So, “let it go, let it go, let it go”. “The perfect” landscape “is gone”. “The past is in the past”. “It’s funny how some distance makes everything seem so small”.Tropical plants and summer annuals do not adapt or harden to withstand temperatures below freezing, and many suffer injury at temperatures below 50°F (10°C). Subtropical plants can harden or acclimate (become accustomed to a new climate) to withstand freezing temperatures, and properly conditioned temperate plants can withstand temperatures substantially below freezing.
Recently planted, unestablished plants may be more susceptible to cold injury. One type of winter injury is plant desiccation or drying out. This is characterized by marginal or leaf tip burn in mild cases and totally brown leaves in severe cases. Desiccation occurs when dry winds and solar radiation result in the loss of more water from the leaves than can be absorbed and/or transported by a cold root system. Plant water needs should be checked after a freeze. Plants may have lost substantial moisture during a windy freeze. Plants will transpire (lose water vapor) on a sunny day after a freeze. Cold injured wood can be identified by lightly scraping the bark with your fingernail and examining the color of the cambium layer (food conducting tissue) just underneath. Green tissue indicates the plant is still alive at that point; black or brown coloration indicates dead or injured tissue. 
After a particularly harsh cold event, some plants may be very slow to recover, so some patience is required. “It will rise” with “the break of spring”. Branch tips may be damaged while older wood is free of injury. Delay pruning until new growth appears next spring to ensure that live wood is not removed. In the meantime, take Elsa’s advice and “let it go, let it go, let it go”. You may be “too relieved to grieve”. I hope I haven’t infringed on any copyrights by letting you know “It’s okay to put off the yard work in the name of plant physiology”.
Enjoy the holiday season!
For more information please see:
Treating Cold Damaged Plants
by Les Harrison | Dec 16, 2014
Some plants will handle freeze events, while other will wither and die. Advance preparation will improve chances of saving sensitive plants from subfreezing weather.
Panhandle Florida gardeners face a new set of challenges annually dealing with the effects of cold weather. A little planning and creativity can make plant protection in the landscape successful.
Many homeowners and landscape managers want to know when plants will need protection. Depending on the plant, a frost warning is a good rule of thumb.
Note 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 happens on clear nights with still air and may even happen when 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. Many tropical plants and fruit trees will survive a few degrees below freezing for brief periods, but extended periods of freeze or heavy frost may require lights or other heat used safely with a cover.
Many time 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 freeze alert.
A few simple actions can save these “green” friends for another year’s enjoyment. Some plants can be moved indoors for the winter and incorporated into the interior décor, rather than cramming them last-minute into a clutter when a freeze looms.
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 are 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 sturdy plants.
A tomato cage or other support structure can be used to keep weight off the plant. Covers also need to be secured at the ground with pins or weights to assure cold air does not creep in from below.
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 tender and tropical plants see another spring in a few more months.
To learn more about protecting delicate plants, see “Cold Protection for Landscape Plants”.
by Eddie Powell | Nov 17, 2014
Northwest Florida homeowners enjoy growing their own vegetables every fall, but are faced with cold weather issues, especially during the first few days of December. For example, most cole crops can be planted until November, but they must be protected from the cold weather or they will need to be replaced. A good variety of cold tolerant plants should be used in order to prevent total devastation of the garden by extremely cold weather.
Below are a few tips to assist the home gardener in growing a successful winter vegetable crop.
- For tender plants, site selection should the top priority when preparing for a freeze. Vegetable plants need a site with good air drainage; not in a low area where cold air settles. Arranging tender plants along a barrier to protect them from cold winds improves the plants cold protection, especially from very hard freezes.
- Poorly drained soils result in weak and shallow roots which are more susceptible to cold injury.
- Plants grown with the correctly applied rate of nutrients will tolerate colder temperatures better and recover from cold injury faster than plants grown with little to no nutrients.
- Watering vegetable garden plants before a freeze can help protect plants. A well watered soil will absorb more solar radiation than dry soil and will radiate heat during the night. This may increase cold tolerance by as much as 2°F.
- Saturated soil conditions can damage the root systems of most plants over a few days, so make sure the ground is well-drained.
- Healthy vegetable plants are more resistant to cold than vegetable plants weakened by disease, insect damage, or nematode damage. Routine inspection for pests and implementation of necessary control measures are essential.
- Plastic or cloth coverings can help protect vegetable plants more from frost than from extreme cold. Covers that extend to the ground and are not in contact with the vegetable plants foliage will reduce cold injury. If the vegetable plant foliage is in contact with the cover it is often cold burned or injured because of heat transfer from the foliage to the colder cover. Some examples of excellent plant covers are cloth sheets, quilts or black plastic. If plastic covering is used, it is extremely important to remove the covering during the day to provide for ventilation of trapped heat.
- Feel free to contact your local county extension office for information on cold protection, pest identification and recommended control measures.
by Matthew Orwat | Nov 17, 2014
Tuesday November 19th and Wednesday November 20th, substantial freezing weather is expected
How cold does it have to get before citrus in Northwest Florida needs to be protected? A concrete answer to this question does not exist. Growers and home gardeners alike must consider several factors including type of citrus grown and the location of the citrus.
Below are a few quick facts to assist growers and home gardeners in determining whether to protect or not to protect their citrus:
- Certain citrus trees such as lime, pomelo, grapefruit, sweet orange, lemon and citron will definitely need protection or need to be moved into a sheltered area. Individuals that grow these types on a consistent basis either wrap their trees with protective covers each season or grow them in containers and move them into greenhouses.
- The meyer lemon, which is in reality a lemon-sweet orange hybrid, is a tree that was introduced to the united states in 1908. Mature dormant meyer lemons can be hardy down to 20°F, with fruit hardy to 26°F. Immature trees, or those that have not reached dormancy, should be protected. Covers made of cloth should be large enough to touch the ground so that heat from the soil can help keep the tree warm.
- Generally, satsuma are cold tolerant down to 15° F, but young trees or trees yet to achieve dormancy are usually only tolerant to 26°F. Fruit should not sustain damage from freezing temperatures above 25°F. Extreme winds sometimes make the effects of freeze events worse, so it is always better to err on the side of protection if the trees are planted in an exposed site.
- Kumquats are the most cold tolerant citrus type grown in Northwest Florida, so protection is not required unless freeze events reach 20°F.
Additional facts to assist the grower or home gardener with citrus protection:
- Plant trees on a south-facing slope, south of windbreaks, on the south side of a structure or under a light canopy if possible. South facing slopes block harmful cold winds. Structures offer radiant heat which aids in the protection of citrus trees. Additionally, light over-story pine canopies allow sufficient sunlight through while reducing frost damage.
- Wrap the trunk with commercial tree wrap or mound soil around the base of the tree up to 2 feet. This will protect the graft of the young tree. Thus, if the branches freeze the graft union will be protected.
- Cover the tree with a cloth sheet or blanket. For additional protection, large bulb Christmas lights can be placed around the branches of the tree. This will increase the temperature under the cover by several degrees. Be sure to use outdoor lights and outdoor extension cords to avoid the potential of fire.
- Water citrus trees. Well watered trees have increased cold hardiness. Do not over-water. If the ground is moist, it is not necessary to water.
- Frames may be installed around young trees to hold the cover. This option keeps the blanket or sheet from weighing down the branches.
- For large production areas, micro-irrigation is an option. This practice will protect citrus trees up to 5 feet, but must be running throughout the entire freeze event. For additional information read this publication on micro-sprinkler irrigation.
- Always remember to remove cold protection once the temperature rises so that the trees do not overheat.
- Do not cover trees with plastic tarp, these will not protect the tree and can “cook” the tree once the sun comes out.
For additional information, contact your local extension office.
by Mary Salinas | Feb 4, 2014
The freezing rain last week across the panhandle left icicles hanging from street signs, rooftops, trees, shrubs and palms. Many people now wonder if their palms will survive the assault of the hard freeze. The chance of survival depends on the following factors:
- the most important consideration is the species of palm; a few of the most cold tolerant that are more readily available are pindo palm, mule palm, European fan palm, Chinese fan palm, needle palm, cabbage palm, and dwarf palmetto
- whether the palm is in an area protected by other vegetation or buildings
- proper fertilization with 8-2-12-4 has been followed
- palms have been properly pruned, i.e. only dead fronds have been removed from the crown (overtrimming by removing green fronds is a stress to the palm)
Icy pindo palm. Photo by Mary Derrick UF IFAS.
The best approach is to leave the palm alone until all danger of frost or freeze is past. Avoid the temptation to remove any of the dead fronds; they will help insulate and protect the meristem, or bud, that will produce new shoots.
If the palm is not too tall, in the spring check to see if the spear leaf (the newest frond that usually stands straight up and has not opened) can be easily pulled out. If the spear leaf does not pull out, the likelihood that the palm has survived is good. Don’t despair if the spear leaf does pull out as the meristem below it may still survive. The best strategy in that event is to remove the dead spear leaf and treat the bud area below the spear leaf with a copper fungicide to reduce the chance of infection of the bud. Be sure to use a copper fungicide and not a copper fertilizer, like copper sulfate.
Once spring comes and you find that the palms have survived, don’t be alarmed if the first new frond is deformed or has dead tips. The fronds that follow will most likely be normal. The palm will be building its depleted food reserves with new leaves so do not remove any fronds that have any green on them whatsoever. All green tissue is making food for the palm and helping it to recover from the cold stress. Only remove fronds that have completely died and have no green tissue.
When temperatures warm and the palms are actively growing, apply a palm fertilizer with the formulation of 8-2-12-4 with micronutrients.
For more information please see the following University of Florida IFAS publications:
Palms for North Florida
Cold Damage on Palms
Fertilization of Field-grown and Landscape Palms in Florida
Pruning Palms
