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woman covering flowers with tarp for cold protection

Cold Weather Alert! Protecting Cold Sensitive Plants

frost on lawn

Frost on lawn. UF/IFAS file photo 12-12-18

What do the different cold alerts issued by the National Weather Service actually mean to homeowners? Frost advisories are given when temperatures expect to fall between 36 degrees to about 32 degrees. This usually occurs as a short term event overnight or in the early morning hours and can be made worse by low to no wind, especially in low lying areas.  A freeze watch  is usually given if the temperature is expected to drop below 32 degrees within the next 24 to 36 hours.  A freeze warning  is given when the cold event is expected to last for a long period of time which can greatly impact commercial crops and residential plants. A hard freeze warning is issued when the temps are expected to drop below 28 degrees for at least several hours or more. These advisories give homeowners time to make preparations to protect cold sensitive landscape plants and outdoor pets.

Frost on car top and windshield early morning February 4th, 2021

Frost on car top and windshield early morning February 4th, 2021, photo by Julia Krochmalny

Indian River County, Florida sometimes experiences extreme winter weather.  Extreme for us means temperatures unexpectedly dipping down to below the freezing point of 32 degrees. This can also happen if the temperature is hovering a few degrees warmer than 32 but with wind causing a wind-chill effect. Conversely, low wind can cause pockets of frost to form. Any of these conditions can wreak havoc with sensitive tropical landscape plants and food crops in our Florida yards.

Examples of landscape plants tender to low temperatures:
  • orchids
  • Angel trumpet, bougainvillea, crinum lily, hibiscus, gardenia, croton
  • subtropical or tropical fruit trees: avocado, banana, citrus, coconuts, guava, mango
  • subtropical or tropical fruits: monstera, papaya, pomegranate, pineapples, passionvine
  • vegetables
  • tender new seedlings & any newly installed plants

    A woman covers plants with a sheet to protect them from frost damage

    Covering plants to protect from cold damage UF/IFAS Photo: Sally Lanigan.

To protect your very tender in-ground tropical shrubs, first give them a good watering and allow to warm in the sun during the day.  Then in the afternoon, cover them with old bed coverings all the way to the ground.  Weigh the edges down with rocks or bricks to keep warmer air from escaping and colder air from infiltrating. Avoid plastic tarps or film which cold can easily penetrate and if touching, can leach out the warmth from the plants and actually increase cold damage!

For very large in-ground plants you can place a large empty rain barrel under the tree or shrub and fill it with water from your outdoor hose.  The groundwater will hold its heat for quite a while, supplying the plant with just enough to keep it from freezing. Some plants, such as banana “trees”, may be covered with a mulch of yard leaves just as high up the trunk as you can pile them.  All of these coverings will have to be removed after the cold weather passes.

Ice covered orange trees

Irrigation used for protecting orange tree groves from a hard freeze. UF/IFAS Photo: Tyler Jones.

In a grove situation, a last resort to an extended freeze is using irrigation so that the whole trees are covered with a thin layer of ice, which will protect the trees from temperatures if they go down into the 20-degree range on the thermometer. This is extremely tricky to do correctly and best left to experienced commercial growers to avoid causing worse damage than if plants were left alone.

Healthy landscapes which are watered, fertilized and mulched properly tend to do better than those which are neglected, left dry and have no mulch.  And tender plants under the cover of a canopy of trees tend not to be affected as much unless there is a stiff wind increasing the cold effects with the wind-chill factor.

To learn more about protecting your plants in the event of cold winter weather, the University of Florida has an EDIS (Electronic Data Information Source) publication titled, “Cold Protection of Landscape Plants“.

The University of Florida “Solutions for Your Life” website has some lawn & garden and landscape information for winter cold events.

To learn more about protecting your Florida ornamental & edible plants from the cold, there is a menu of UF/IFAS EDIS cold protection publications on their EDIS website under “Cold Protection“.

And once the cold event is over, be sure to scout your yard for any damage and consult the University of Florida’s EDIS site for help in recovering.  Many landscape plant which look dead after a frost may recover with the proper care.  The UF EDIS publication, “Cold Damage on Palms” can help you know how to help your palms recover from a freeze or if they can recover.  For more on cold damage & chilling injury, EDIS has a menu list of Cold Damage publications to help with that too.