As the winter months approach, don’t let Jack Frost catch you off guard. We may not have to deal with too many days or nights with freezing temperatures in the South, but they do still occur. But no need to fret, with just a little bit of preparation and maybe even some ingenuity, your precious blossoms won’t just survive but can still thrive after a sample of winter weather.
What is frost and what can it do to plants?
The freezing point is 32°F, yet frost can occur when air temperatures are slightly above 32°F but plant tissues drop to 32°F or lower. Damage to plants occurs when one of two types of freezing or frost events happen:
- Radiational frost or freeze occurs on clear nights when the heat rises into the atmosphere, leaving surfaces colder. Tree canopies can help reduce radiant heat loss from the ground when radiation frost threatens your garden.
- Advective frost or freeze happens when a cold air mass moves in, creating a drop in temperature. Windbreaks such as fences, buildings, or temporary coverings can help save your garden from advective frost.
Frost advisories
Frost Advisory: An advisory is announced when temperatures are expected to fall to between 36°F and 32°F.
Freeze Warning: A warning is isseud when there is at least an 80% chance the temperature will fall to 32°F or lower.
Light Freeze: Happens between 29°F and 32°F and can kill tender plants.
Moderate Freeze: Is widely destructive to most vegetation and occurs between 25°F and 28°F
Severe or Hard Freeze: 25°F and colder, and can cause heavy damage to most plants.
Planning a frost-tolerant garden
Site selection
Location, location, location. When planning your garden, make sure you take time to evaluate your land and understand the areas most prone to frost development. Take note of low-lying or shadier areas where Jack Frost is most likely to nip at your budding blossoms.
- You’ll want to determine the coldest and warmest locations on your property so you can plant accordingly. The coldest spots are typically found on the north and northwest parts of a property, in low areas. The warmest area is usually going to be the southern part of the property.
- Also, know and understand the microclimates of your yard. Elevation, landform, soil, properties, canopy cover, and proximity of structures or other plants all play a role in the microclimates on your property. This information is helpful when selecting placement for cold-sensitive plants. Place these plants near the part of the house that receives southern exposure or near larger plants or other structures.
Plant selection
Know your USDA plant hardiness zone and select plants that meet minimum requirements for cold-hardy plants for your area. Don’t forget to account for both the hot temperatures of the summer as well as the cold temperatures in the winter.
Plant nutrition
Naturally, healthy plants are more likely to survive cold temperatures than plants struggling to maintain their health.
- Fertilizing at the proper time of the year is crucial. Fertilizing in the fall, after August or September, with a fertilizer high in nitrogen can cause new growth that is vulnerable to cold temperatures.
- Soil sampling is the best method to determine a plant’s specific nutrition needs for the type of soil in your yard. For more on soil pH and how to test your soil see this article from Lawn Love.
Shading
Be sure to place plants according to their preferences for shade or sun exposure to produce healthy plants that will be more likely to survive a sudden temperature drop.
- If improperly sited, a plant that prefers full sun will not do well in the shade and will be less tolerant of cold temperatures.
- Also good to keep in mind when planting is that shaded areas are less susceptible to winter dehydration than those in the full sun.
Windbreaks
Fences, buildings, evergreen plants, and temporary structures are useful tools for protecting vulnerable vegetation.
- Windbreaks are most useful in reducing injury caused by cold winds and advective freezes.
- Place a windbreak anywhere brisk winds can be a problem, typically the northwest side of the plant.
How to prepare for a freeze
When the weather forecast is calling for a late spring frost or freeze there are numerous ways to protect your freshly planted veggies from the cold night ahead.
Heating and covers
When it comes to frost protection for your home garden there are a number of easy DIY options suitable for whatever garden plants you may have recently planted.
Plants in containers
These plants are particularly susceptible to frost damage as their roots are exposed since they are above ground.
- Move plants in containers inside a protective structure (house, garage, greenhouse, or shed) or drape a covering over them.
- Push together containers left outside and mulch or cover them.
- Wrap the bases of containers in plastic, burlap, or blankets.
In-ground plants
Plants with their roots in the ground are more protected by heat radiating from the soil. But they, too, may need protection from the cold weather, particularly tall and more open plants.
- Cover plants with old bed sheets, blankets, or cardboard boxes. Plastic sheeting is not recommended. Be sure to remove the plant cover during the day to provide ventilation.
- If wind is predicted, you may want to get some stakes and create a tent-like structure to cover your plants and secure the sides of the covering to be sure it isn’t blown up and away in the middle of the night.
- Use PVC or similar material to build a frame around the plant to place the cover on in order to keep it from coming in contact with the foliage and possibly breaking delicate leaves and stems.
- Old bed sheets and blankets can also be used to wrap the bases and trunks of young, tender trees.
Cloches
These glass or plastic covers work like mini-greenhouses. They protect small individual plants or young vulnerable plants from the harsh weather conditions a late-season cold front may bring. Check out this article for the history of these bell-shaped glass covers. Today gardeners can easily DIY cloches from plastic jugs.
- Cut off the bottom of a milk jug, water bottle, or any other kind of plastic bottle or jug. Then place over the tender plants you want to protect.
Water and mulch
Check the watering needs of plants prior to a predicted cold snap and water if necessary before turning off your irrigation system.
- Watering the roots of the plant will insulate it, helping to prevent frost damage. The moist soil absorbs more heat helping to maintain an elevated temperature around the plants.
- Adding a 2-3 inch layer of mulch around the base of plants can also help plants retain moisture and heat. However, don’t mulch up to the bark of trees and shrubs.
Heat lamps
Many garden nurseries and home improvement stores sell heat lamps. These are essentially weatherproof lamps that use infrared (heat-emitting) lights to provide warmth to nearby plants. If you’re considering investing in heat lamps, it’s important to weigh the cost versus replacing the plants. If your plants are inexpensive and easily replaced, a heat lamp might not make sense.
After the freeze
- All parts of a plant including its fruit, stems, leaves, trunk, and roots can be impacted by frost damage. However, there may not be any visible signs of injury for several days or weeks.
Signs of damage
- The first visible signs of possible frost damage may appear on the leaves and stems. This can look like leaf scorching or leaf-tip burn.
- Leaf damage may also appear as obvious black or burnt foliage, usually occurring at the tip of the branches.
- Roots that receive damage from freezing temperatures may wait till temperatures rise and the demand for water increases before they begin to show signs of distress.
- To determine if your plants were damaged, wait several days after the cold weather has departed, then remove several buds and stems.
- Cut a cross-section of the bud’s top using a sharp knife or razor blade. If there is any discoloration in the bud, they have been damaged.
- To determine if the stems were injured, peel the bark back to reveal the layer directly under the bark. If there is any black or brown discoloration, damage has occurred.
- The good news is that damage to buds, stems, and leaves may be localized and the entire plant might not be affected.
Types of damage and conditions
- Plant tissues die when ice forms within a plant’s cells causing leaves or stems to become brownish-black mushy.
- Desiccation happens when a plant’s water loss exceeds absorption leading to the drying out of the plant. Windy conditions and cold can cause damage from desiccation.
- Injury from frost can lead to a reduction or even a total loss of blooms the following spring.
- Bark splitting is seen from loose bark in various areas on the trunk. It can cause structural damage and reduce the plant’s ability to transport nutrients and water which ultimately can lead to the death of the whole plant.
- Frost canker can appear as a darkened, moist area.
- Frost crack is when a long, deep, narrow crevice running up and down the trunk of a tree appears.
Recovery
- Wait to prune until after the last frost dates have passed to be sure you don’t accidentally remove living wood. If localized damage has occurred to foliage or stems, prune several inches below injured tissue.
- In the days after a freeze, watering plants will give them needed water and it will also help thaw the soil. After a freeze, especially on a sunny day, plants can lose water because the water in the soil or container may still be frozen.
Final thoughts
After a long, hot summer, don’t let all that sweat be for nothing. Just a little preparation will keep your garden looking beautiful all year long. If you need expert help with your garden, consult one of our Lawn Love gardening specialists.
Main photo credit: Pxhere
