WINTER PLANT PROTECTION METHODS
Move plants in containers into protected areas where heat can be supplied or trapped. If you have to leave containers outdoors, push them together and protect with mulch to reduce heat loss from the container walls. (Note: Leaves of large canopy plants may be damaged if crowded together for extended periods.)
Heat radiates from soil surfaces during the night and is mainly lost to the atmosphere unless it is trapped. Reduce radiant heat loss and protect plant roots by placing mulch around the plants. For perennials, the root system is all that needs to be protected.
Coverings protect more from frost than from extreme cold. Covers that extend to the ground and do not touch plant foliage can lessen cold injury trapping heat. However, be careful when putting using plastic as a cover because foliage that touches plastic coverings is often injured since the cover actually takes heat away from the plant.
Examples of coverings include cloth sheets, quilts, plastic, or commercial frost cloths. Remove plastic covers during a sunny day or provide ventilation to keep the air under the cover from heating up too much. Putting a light bulb under a cover is a simple method of providing heat to ornamental plants in the landscape.
Here in Ocala, zone 9A, we recommend that you use white covers rather than darker colored covers - you can usually find them on amazon for about $20 to $30 for a 10 x 30 foot cover.
WHAT TO DO AFTER THE FREEZE
When the temps warm up - usually 10 to 15 degrees above freezing - take those covers off! Leaving the covers on, especially on a sunny day and even more so if you used a dark material to cover the plants, will harm them too. If more cold weather is expected again, pull back the cover for a few hours and water if necessary.
After a freeze, especially on a sunny day, plants can lose water because the water in the soil or container medium is frozen. Watering the plants will give them available water and will also help thaw the soil.
After a freeze, you can remove dead leaves once they turn brown. You should wait to do any severe pruning until new growth appears. This way you can be sure you are not removing any live wood and damaging the plant even more.
Sometimes cold injury isn’t as obvious. For instance, two symptoms of cold injury are a lack of spring bud break and/or an overall weak appearance. On woody plants, the cambium layer under the bark will be black or brown if a branch is damaged.
Luckily freezes don’t happen too often, which means Florida gardeners can still grow the tropical and subtropical plants that wouldn’t survive in other states. But that doesn’t mean freezes do not pose a threat to your landscape. Follow weather reports and protect and prepare vulnerable plants accordingly before freezes take them by surprise
For more information on winter plant protection, cold-hardy plant varieties, and other winter landscaping questions, contact your local Extension office.
Adapted and excerpted from:
D. Ingram and T. Yeager, "Cold Protection of Ornamental Plants" (ENH1), Environmental Horticulture Department (reviewed 10/2003 and 02/2010).