Understanding Cold Protection

Understanding Cold Protection

Freeze warning is a terrifying phrase for gardeners. Cold damages your plants and may even kill them outright. Understanding how plants freeze will help you create mitigating strategies for their preservation. Informing yourself as to how freeze damages plant tissues will allow you to fortify your garden.

How do Plants lose Heat

Cold exposure happens in a couple of ways. Radiant heat loss occurs when one surface emits waves of heat into a colder surrounding environment. The surfaces of leaves and stems are not immune to this type of temperature transfer, nor is the soil in your garden beds. Frost may or may not form depending on moisture levels in the air, but cold damage will still be the result. The other main source of heat loss in gardens is through Advective freezes. These occur when cold air from the north moves south en masse resulting in colder temperatures and often increased winds. Mitigating this is a little tougher than radiant losses but not impossible  

IFAS Photo

As with all things, planning is at the forefront. When designing your garden, cold hardiness should be considered. Certain plants naturally handle cold weather better than others. Utilizing native plants and those specified for your USDA hardiness zone will keep gardens alive in winter months. These tend to be acclimated for colder temperatures. Once the proper plants are selected and planted, ensure they are properly treated. Keeping your plants as healthy as possible is also critical in cold tolerance. Mulches and watering prior to a freeze event will reduce risk from radiant heat loss. The water absorbs warmth through the day and holds onto it more efficiently than dry soil would. Addition of a frost blanket will further reduce heat lost and ultimately the damage to your plants. A slightly more in-depth protection method comes from establishing microclimates in your yard. Use taller trees and windbreaks.  Taller trees create a canopy that blocks heat loss to the atmosphere. Windbreaks keep the colder air away from your gardens and again prevent heat loss. None of these methods are fool proof but will help keep your gardens alive through the colder months. You may still experience damage from freezes. If this does happen, make sure your plants are watered to thaw any roots ensuring they function properly. Inspect stems by scraping a little tissue. Prune away any that shows black or brown tissue while keeping any which still looks green.

IFAS Photo

Summing up

Freezes can be devastating to your gardens. A little knowledge can go a long way toward mitigating loss.  For more information on cold protection, see this Ask IFAS document, or contact your local extension agent for additional information on this and any topic regarding your gardens and more.

Gardening in the Panhandle LIVE Program Summary: Subtropical Fruit

Gardening in the Panhandle LIVE Program Summary: Subtropical Fruit

The Q&A on Subtropical Fruits offered valuable information on many types of subtropical and temperate fruits of interest to homeowners.  Below are the reference materials related to specific questions that were asked along with notes from the panel discussions.

How to protect tropical and subtropical fruit trees from freezes?
Freeze protection of TF crops outside of Miami-Dade County: https://www.youtube.com/watch?v=e1U7CrqX074

Cold protection in South Florida is mainly through irrigation practices. It takes irrigation to run before freeze and continue until freeze is over.

What are the easiest subtropical fruits to grow?
Loquat: https://edis.ifas.ufl.edu/publication/MG050
Home Citrus Culture Publications – UF: https://edis.ifas.ufl.edu/entity/topic/citrus_home_citrus_culture

What are the best citrus trees to grow on NE Florida?
Tangerine, Mandarin (Owari and Brown select mandarins), & Tangelo Varieties: https://edis.ifas.ufl.edu/entity/topic/tangerines_mandarins_tangelos

Can we grow papayas here?
Growing Papaya in the Home Landscape: https://edis.ifas.ufl.edu/publication/MG054

Papayas are grown from a seed, not from air layering or grafts. There are some disease issues from Papaya ringspot virus. May have to start new plants. Less than a year from seed to fruit. Seed can be all male, all female, or have both male and female flowers. Need to get rid of the males. Male flowers hang off the tree where females stick to the stem more.

What are the best varieties of limes to grow in the Panhandle?
Growing “Tahiti” Limes in the Home Landscape: https://edis.ifas.ufl.edu/publication/CH093
Tahita and Persian limes are in retail nurseries. These are cold sensitive so plant in protected areas. Key limes would need to be in a container for most people.
Rangpur lime is a lemon and mandarin cross.

Bananas continually produce nice foliage but do not form fruit in 5 years.  What to do?
Maybe not spend any more time trying to get fruit. If the bananas are in a large clump, you don’t want to have a large clump. Cut them back so that you have 3 bananas, one large, one medium, and one small so that you get lots of light. That is the key to fruit. Remove brown leaves.

Can we grow a Barbados cherry successfully?
Malpighia glabra, Barbados Cherry: https://edis.ifas.ufl.edu/pdf/FP/FP39000.pdf
Small tree to about 6 feet x 6 feet. Mild flavor. Not really suitable for North Florida. Needs sunlight for fruit.

Can we get the transgenic papaya that is immune to the Ringspot virus?
TREC Fruit Specialist has the papaya but it is not legal to introduce them into Florida at this time.

Advice on growing kiwi vine.
Growing Kiwis in FL: https://nwdistrict.ifas.ufl.edu/hort/2019/04/09/kiwis-a-golden-opportunity/
Temperate fruit that requires chill hours. Golden varieties developed by Auburn University. AU Golden Dragon and AU Golden Sunshine. Need a substantial trellis. Male and female vines so male vine for every 2-3 females.

Crestview gets fairly cold in late winter. What fruit trees do well here?
Dooryard Fruit Varieties: https://edis.ifas.ufl.edu/pdf%5CMG%5CMG24800.pdf

Will Papaya fruits reach maturity in NW Florida?
Growing Papaya in the Home Landscape: https://edis.ifas.ufl.edu/publication/MG054

Papayas do not like the cold. Probably not likely to produce a fruit but can give it a try.

What about pineapples?
Good option in a container. Bromeliad that is terrestrial that is watered through the roots.

I planted an arbequina olive tree and it’s struggling. Keeping in pot and protected from freezing but not thriving.
Olives for Your FL Landscape: https://edis.ifas.ufl.edu/publication/EP515

Olives like a more consistent temperature than the Panhandle offers. Needs excellent drainage.

Mexican avocado has survived freeze and flooding but still not thriving. Why?
Avocado IPM: https://trec.ifas.ufl.edu/tropical-entomology/index.php
Hass avocado, smaller ones from CA and Mexico. South Florida is too warm to grow Hass but it may work in North Florida. Green skinned avocado is grown in South Florida. More tasty. Florida avocados need a little cool weather to initiate flower and then fruit.

Avocados will not like wet soils.

Will lychee and avocado grow in Pensacola?
Red fruit, white inside, similar to a grape but sweeter. Needs chill hours. 2018 lychee mite came into Florida and now in 13 counties. Difficult to manage.

Shade-tolerant subtropical fruits?
Fruit needs sun. Monstera deliciosa, Swiss cheese plant, produces an edible fruit grows in shade. Definitely needs protection. DO NOT eat fruit early or you will have mouth pain. Fruit should be falling apart.

Pawpaw is not tropical but grows in shade.

How to trim fruit trees?
Hand pruning and training of tropical and sub tropical fruit trees: https://edis.ifas.ufl.edu/publication/HS1372

Often prune for size control in South Florida to encourage lateral growth and get sunlight into the center.

Which banana trees thrive here?
Banana Growing in the Florida Home Landscape
https://edis.ifas.ufl.edu/publication/MG040

What subtropical fruits are garnering the most interest in the panhandle right now?
Loquat Growing in the Florida Home Landscape: https://edis.ifas.ufl.edu/publication/MG050

Mangos are of most interest in South Florida

What about akee?
Caribbean fruit related to lychee. Do not eat before ripe or you will die.

The good pH for blueberries and raspberries
Blueberry Gardener’s Guide: https://edis.ifas.ufl.edu/publication/MG359

What plum varieties are recommended?
Fruit Tree Recommendations for AL: https://ssl.acesag.auburn.edu/pubs/docs/A/ANR-0053-F/ANR-0053-F-archive.pdf

Finger limes are the new hot crop at the TREC.

Protect Your Winter Garden and Landscape Plants with Frost Cloth

Protect Your Winter Garden and Landscape Plants with Frost Cloth

Use frost cloth to completely cover cold sensitive plants. Be sure to make complete contact with the ground and use heavy objects to keep the fabric secure. Photo by Jonathan Burns.

Use frost cloth to completely cover cold sensitive plants. Be sure to make complete contact with the ground and use heavy objects to keep the fabric secure. Photo by Jonathan Burns.

 

One major aspect that separates North Florida from South Florida is the discrepancies in air temperature. Although the differences are relatively small when comparing Florida with northern states, they can mean a world of difference in the plant world.

Even hardy cauliflower leaves can be damaged by cold winter nights in the Florida Panhandle. Photo by Molly Jameson.

Even hardy cauliflower leaves can be damaged by cold winter nights in the Florida Panhandle. Photo by Molly Jameson.

In most of North Florida, our USDA plant hardiness zone is 8b, which means average minimum winter temperatures are between 15 and 20° Fahrenheit (F). We therefore can experience hard freezes, which happens when temperatures are below 28°F for over five hours. These types of conditions are capable of “burning” the leaves of even the toughest winter vegetables.

Fortunately for our winter gardens, average minimum winter temperatures are in the lower 40s, high enough not to damage winter garden crops. When we do have lows close to or below freezing (32°F), there is one very cost-effective method that can help keep crops and landscape plants protected. This is the use of a material called frost cloth.

Frost cloth can moderate air temperatures six to eight degrees. Photo by Turkey Hill Farm.

Frost cloth can moderate air temperatures six to eight degrees. Photo by Turkey Hill Farm.

Frost cloth, which can be purchased at most plant nurseries, is a breathable polyester fabric that is light weight and heat retentive. When used correctly, it can moderate air temperatures about six to eight degrees. This is typically all that is needed to get us through our mild North Florida winters. It is also relatively inexpensive, and if cared for, the same cloth can be used for many winter seasons.

Large blankets or bedsheets can be used as frost cloth substitutes, but whether you are using actual frost cloth, or something pulled from the linen closet, it is very important to use it correctly to be effective. The cloth must touch the ground at all points, as it works by trapping heat that radiates from the soil. It also increases the humidity around the plant, aiding in temperature moderation.

"Lollipop" trees will allow the heat from the ground to escape, giving the tree no cold protection. Photo by Jonathan Burns.

“Lollipop” trees will allow the heat from the ground to escape, giving the tree no cold protection. Photo by Jonathan Burns.

For sensitive landscape plants and fruit trees, it can be more difficult to fully cover the plant with the frost cloth to trap the heat, but it is just as important. When driving around town on a cold night, I inevitably encounter a few “lollipop” trees. This is when the foliage of the tree is wrapped in frost cloth, but the cloth does not reach the ground, and is typically tied off at the upper trunk of the tree. All heat moving upward from the soil will go right around the cloth, giving the tree essentially no protection.

Wire or PVC hoops can be used to help secure frost cloth and keep the cloth from damaging sensitive plant stems and leaves. Bricks, sticks, soil, or garden staples should be used along the perimeter of the frost cloth to prevent nighttime gusts from blowing the cloth off your garden beds or landscape plants. In the morning, remove the cloth once air temperatures reach about 50 to 60°F.

To learn more about cold protection, check out the UF/IFAS EDIS publication, Cold Protection of Landscape Plants (https://edis.ifas.ufl.edu/publication/MG025).

When is the Correct Time to Harvest Satsumas?

When is the Correct Time to Harvest Satsumas?

Fall 2016 Satsumas. Image Credit: Matthew Orwat

    Fall 2016 Satsumas. Image Credit: Matthew Orwat

One question that repeatedly pops up in my Extension work is “When do I harvest fruit or vegetable X ?”  This fall, the question of “when should I harvest my citrus?” has been a choice topic! The most common citrus in the Florida panhandle is the satsuma, Citrus unshiu, so it makes sense to limit this article to that species.

Harvesting satsumas can be a confusing activity for new citrus enthusiasts. Fall seasons in the panhandle tend to be extremely variable, from cold and wet to warm and dry or any combination thereof. To complicate matters, citrus is often grown in a protected microclimate in the garden. Thus, another variable is added to the decision tree.

Some harvest considerations to take note of:

  • Sometimes the fruit is ready to harvest even when some green remains on the fruit
  • Not all fruit on a given tree will be ready at the same time
  • It’s a good idea to harvest a few fruit per tree and taste test….this will be a good indicator of the readiness of the other fruit on the tree
  • A general trend to consider is that the longer the fruit remains on the tree, the sweeter it will become

Image Credit Matthew Orwat

Image Credit Matthew Orwat

When satsuma ripen, they become slightly soft. That’s a good indicator that they are ready to harvest. This softness makes them extremely easy to peel but poses a challenge when harvesting. If they are simply pulled off of the tree, some peel will be left on the tree and the fruit will be compromised. Such a fruit would have to be consumed quickly. To solve this problem satsuma are clipped off the tree, leaving a tiny bit of stem attached to the fruit. This allows the fruit to be stored and transported.

When a hard freeze is approaching (5 hours below 28ºF), it is important to harvest the fruit before this event whether or not they are ripe. Hard freezes will ruin the texture of the fruit and cause them to begin the rotting process.

Since a hard freeze is forecast for Friday December 9th 2016 for part of the Florida Panhandle, consult your local weather forecast and make your decisions accordingly.  For an in-depth discussion on citrus fruit harvesting and cold tolerances, please consult this publication from Texas A& M University. Additional articles are available on cold protection and frost readiness here.

 

Cold Protection for the Winter Garden

Cold Protection for the Winter Garden

Covering a row of lettuce with frost cloth at Turkey Hill Farm. Photo by Turkey Hill Farm.

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.

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.

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.