by Les Harrison | Jan 20, 2016
North Florida’s gardeners are facing 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.
Covering plants to protect from frost. UF/IFAS Photo: Sally Lanigan.
Many homeowners and landscape managers want to know when plants will need protection. The point of freezing is a good rule of thumb for most temperate zone plants.
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.
Some plants can be moved indoors for the holidays and incorporated into the interior décor, rather than cramming them last-minute into a chaotic bundle when a freeze looms.
Get prepared by identifying old sheets, blankets and drop cloths which can be used as covers for tender or tropical zone 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 tender and tropical plants see spring 2016.
by Molly Jameson | Nov 4, 2015
Covering a row of lettuce with frost cloth at Turkey Hill Farm. Photo by Turkey Hill Farm.
While most of Florida does not have to worry about freezing winter weather, the Florida Panhandle is certainly an exception. North Florida experiences a few hard freezes – temperatures less than 28°F for over five hours – every year. Although most of our cold weather occurs in January and February, we can expect our first frost around the second week of November. Therefore, it is important for gardeners to be prepared.
Most of the Panhandle is in zone 8b, which means average minimum temperatures are between 15 and 20°F. Nights – especially consecutive nights – that get this cold can “burn” the tips of even the toughest vegetables, such as collards and kale. It is also important to remember that if you live in a more rural area, temperatures will be slightly cooler, relative to the city. Frost is also more likely to occur on clear nights, as heat that radiated down from the sun during the day will escape the atmosphere at night, if clouds are not present. Also, if you were late getting your fall garden started, it is even more important to protect your vegetable plants, as young plants are more susceptible to cold weather.
Young plants are more susceptible to cold weather, so be sure to use cold protection. Photo by Molly Jameson.
One strategy home gardeners can use to protect their plants during cold weather is to use frost cloth. Frost cloth is a breathable polyester fabric that is light weight and heat-retentive. It can moderate temperatures about six to eight degrees Fahrenheit. Use it on all of your garden plants if there is a hard freeze, but do not cover cold hardy vegetables in mild frosts, as their flavor can actually become sweeter in cool weather, and the plants will become more tolerant to the cold.
Frost cloth can be found at most plant nurseries, and it can last multiple years if you take care of it. Use wire hoops to keep the cloth off smaller crops, as ideally the cloth should not touch the plant. Most importantly, the cloth must touch the ground at all points to be effective, as it works by trapping heat that radiates from the soil and increases the humidity around the plant.
In the morning, do not remove frost cloth too early, as quick thawing can actually cause the most severe damage. Wait until the outside air temperature is about 50 to 60°F. Since frost cloth is breathable, if temperatures do not reach 50 to 60°F during the day, you can leave it on multiple days.
Frost cloth in high tunnel at Turkey Hill Farm. Photo by Turkey Hill Farm.
Sheets or blankets (not plastic) can be a frost cloth substitute, but there are disadvantages, such as not allowing proper air circulation or not being large enough to reach the ground.
Another strategy that can help keep your garden safe from cold weather is to keep your plants well watered, as frost damage is actually dehydration. When ice crystals form on the leaf surface, it draws moisture from the leaf tissue. Damage will therefore be less severe if the plant is not already drought-stressed. You can also mulch around the base of your plants with wood chips or straw to help moderate soil temperature and retain moisture.
Being prepared for cold weather will help keep your vegetable garden going strong all the way into the spring. Remember that healthy plants will be more resistant to cold weather than unhealthy plants, and investing in a few sheets of frost cloth can go a long way to ensure your veggies survive our chilly North Florida winters.
by Eddie Powell | Jan 22, 2015
Florida homeowners enjoy a wide range of landscape and citrus plants and often times desire a tropical or semitropical appearance to their landscapes. Many landscape plants are often planted past their northern limit such as here in Northwest Florida, although microclimates differ dramatically. Tropical and subtropical plants can be used in the landscape, but they must be protected or replaced if necessary during cold weather. A good variety of tender and hardy plants should be planted in order to prevent total devastation of the landscape by extremely cold weather.
The site selection for tender plants should be number one on your list when preparing for a freeze. Tender ornamental plants need a higher site with good air drainage, and not in a low area where cold air settles. Arranging tender plants along fences or other barriers to protect them from cold winds improves the plants’ cold protection, especially from very hard freezes.
Poorly drained soils result in weak 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 or no added nutrients. Be aware that late fall fertilizing of nutrient deficient plants or fertilization before unseasonably warm periods can result in a late growth which is more susceptible to cold injury.
Ornamental plants that are planted under large tree canopies can have more cold protection and require less cold prevention for the owner.
Watering landscape plants before a freeze can help protect plants. A well watered soil will absorb more solar radiation than dry soil and will reradiate heat during the night by as much as 2°F . However, saturated soil conditions can damage the root systems of most plants over a few days, so make sure the ground is well drained.
Avoid late summer or early fall pruning which can alter the plant hormonal balance resulting a flush of new growth. This new growth is more susceptible to cold injury. Healthy plants are more resistant to cold than plants weakened by disease, insect damage, or nematode damage. Routine inspection for pests and implementation of necessary control measures are essential.
Here are a few methods for plant protection. Plants in pots or containers must be moved indoors where heat can be available to them. Containers that have to be left outdoors should be protected by mulches around the container or root ball of plants in the landscape to reduce heat loss from container sidewalls.
Cold Protection for Veggies!
Coverings can help protect plants more from frost than from extreme cold. Covers that extend to the ground and are not in contact with plant foliage can lessen cold injury to the plant. Foliage in contact with the cover 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 ventilation of trapped heat. A light bulb under a covering also is a simple method of providing heat to ornamental plants in the landscape during the night hours.
Cold Damage on Fruit Tree
Pictures By Eddie Powell
Immediately after the frigid weather has passed, plants need to be checked for water loss. The foliage could be losing water vapor or transpiring on a sunny day after a freeze while water in the soil or container medium is frozen. Apply water to thaw the soil and provide available water for the plant. Soils or media with high soluble salts should not be allowed to dry out because salts would be concentrated into a small volume of water and can burn plant roots. Root burn can cause the roots to dry out and not take up water to the plant.
Pruning should be delayed until freezing temperatures have risen or until new growth appears to ensure that live wood is not removed. Dead, unsightly leaves may be removed as soon as they turn brown after a freeze if a high level of maintenance is desired. But it is best to wait until the threat of freezing weather is gone. Cold injury may appear as a lack of spring bud break on a portion or all of the plant, or as an overall weak appearance. Cold injury is usually found in the upper portion of the plant. Branch tips may be damaged while older wood underneath is free of injury. Cold injured wood can be identified by examining the cambium layer under the bark for black or brown coloration. Prune these branches back to a bud 2-3 inches behind the point of discoloration.
For more information on freeze protection of plants see:
Cold Protection of Landscape Plants
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.
