Frost damage and 5 tips on what to do about it

1. Know what zone you live in and plant responsibly.
The USDA has a list of regional temperature zones (or plant hardiness zones) mapped out which clearly shows an areas average temperature ranges. This is very important not only for farmers and plant nurseries but also for the average backyard gardener. Most retail nurseries will provide plant labels on their plants which tell which zones the plant will grow best in. Knowing your planting zone is key. Here is a link to see what zone you live in: http://planthardiness.ars.usda.gov/PHZMWeb/
The Sunset Western Garden Book (a horticulturalists handbook for many years) also has its own classification for plant hardiness zones which is different from the USDA list. Both are excellent resources. Be sure to know which zone you reside in and responsibly plant only those plants which will grow successfully there.

2. Plant appropriately.
Plant full sun-loving plants in full sun locations. Plant partial sun-loving plants in partial sun locations and plant shade-loving plants in full shade locations. I know this sounds elementary but you would be surprised on how easy it is to incorrectly locate a shrub in the garden. The sun’s angle is constantly changing through the seasons and this gives an added challenge to most homeowners and untrained landscapers.

3. Keep a keen eye on the weather forecast.
Prevention can help a lot. Be on the defense against every cold front during the winter and early spring. Knowing ahead of time which plants are more frost sensitive will help you to prepare in advance of a frosty evening. A little cold or frost will not normally cause severe damage to a shrub, but a prolonged period of at or below freezing temps often will.

4. Actively cover your sensitive plants.
Cover your frost sensitive plants with a breathable cloth blanket before it gets dark. Something lightweight like a bed sheet or cloth filter fabric or even burlap work great. Some retail nurseries will sell special shrub cloth bags. There are lots of on-line products available as well. Stay away from anything heavy as this could cause damage to your branches especially if it gets wet. Also stay away from using plastic. Although plastic sheeting is a great lightweight cover it could build up condensation against the plant which can freeze and cause even worse damage. Be sure to secure the covering incase it becomes blustery overnight. Remember, plants need to breath too! Remove the covering in the morning if the threat of frost has passed so your shrubs can enjoy the sunshine during the day.

5. Avoid the cut-back.
This is probably the number one reason most folks lose their specialty plants after a frost. Although a plant may suffer tremendous frost damage, oftentimes it is only the outer foliage or branch tips which will die leaving the core trunk and root system intact to regenerate new growth in the spring. This is especially true with most vining shrubs like Bougainvilleas. KEEP THE OUTER DAMAGED FOLIAGE INTACT and diligently continue to cover you plant throughout the winter. This outer foliage, although ugly, will continue to protect the core of the shrub against further cold snaps.
Here in So. Cal. the threat of nighttime frost usually ends in May. I suggest waiting until late April-early May to cut your frost damaged plants back. I know it seems like a long wait to cut that ugly foliage away but your patience will be rewarded when your specialty shrubs survive that “once in a decade” cold spell.
By following these helpful tips, your frost sensitive shrubs will be able survive the winter chill and “grow on” to provide lush foliage and beautiful color for you again in the spring.

Contact the author, Brad Gore of Gore Planning, Inc. at goreplans@gmail.com with any questions or comments.