Protecting plants from frost damage is crucial to ensure their survival during the spring season. Frost can occur unexpectedly (I know it’s a stretch to suggest it’s unexpected in January and February) and can cause significant damage to newly established plants.
However, there are several preventative measures that can be taken to protect your plants such as providing insulation with frost blankets or mulch and positioning plants in protected areas. Learn more about how to protect your garden plants from frost damage with our expert tips and advice.
The cold, cloudless evenings of winter, spring and autumn may be hazardous to the health of your plants. During the day, your plants and the soil absorb and store heat from the sun. As the day turns into night, your plants quickly begin to lose all of their stored heat. Clouds will help to insulate and slow the loss of heat, but a cloudless, wind-free night will afford no protection at all. The temperature within the soil and in the plant’s cells may even drop to a few degrees colder than the air.
As the temperature drops, the moisture in the air condenses into dew, which then freezes when the temperature reaches 32°Farenheit on the plant surfaces. At 32° degrees, damage to most plants may be minimal and only affect a leaf or two. However, if the temperature drops far enough for the plant cells to freeze, non-hardy plants will die.
Weather conditions can bring about a frost, even in supposedly frost-free areas. It is important to heed the warning when your local forecaster announces ‘a chance of frost’, and take precautions to protect your garden. It is possible to extend your growing season by several weeks if you are able to keep your plants alive through a single early frost!
Helping your garden survive a frost
The best way to avoid frost damage to your plants is to grow plants that can withstand the frost. The term ‘frost hardy’ is often misleading because of the degrees of frost (i.e. light frost vs hard killing frost). It is a good idea to ask an expert at your nearest nursery what is suitable to grow in your area. Even better, look around your own neighbourhood and see what survives and thrives in other gardens.
Plant varieties of plants that flower late, in areas where late spring frosts may occur. Often a plant will survive frost on the foliage, but the same frost would kill any flower buds that have emerged.
Because cold air, being denser than warm air, sinks, low-lying areas of the garden can be several degrees colder. Consequently, frost may occur in these areas when there is no frost evident anywhere else in the garden. Plant tender species on higher ground or on slopes where the cold air will flow past the plants as it moves to the low point. Any sloping area is less prone to frost because the cold air can’t settle there as easily.
Precondition your plants to withstand cold temperatures by discontinuing fertilising in early September so that no new foliage is on the plant when cold temperatures arrive. Older leaves are much tougher and more able to withstand a frost.
When cold weather is forecast
When the inevitable occurs and a frost is predicted, there are several things that you can do to protect your plants.
- Water the garden a day before predicted cold weather. The soil will release moisture into the air around your plants during the night, keeping the air somewhat warmer.
- Even a slight breeze will prevent cold air from settling near the ground during the night. You can help keep frost from forming by providing this breeze artificially with a solar-powered fan or windmill. Energy stored through the day will be expended through the night to keep the air moving around your plants.
- Cover up before dusk! By the time it gets dark much of the stored heat in the garden has already been lost. If you have time, build a simple frame around the plant, or row of plants. (Even a single stake can be used in many cases.) Then drape a cover of newspaper, cardboard, plastic tarps, bed sheeting or any other lightweight material over the frame to create a tent. If you don’t have time to create a frame, lay the protective cover directly onto the plant. This will help to slow the loss of heat rising from the foliage and the ground. Remove the covers in the morning, once the frost has thawed, to let the light and fresh air back in, and to prevent overheating by the sun.
For smaller individual plants you can use jam jars, milk jugs with the bottom removed, paper cups or upside-down flower pots as heat traps. Don’t forget to remove these covers in the morning.
You can collect heat during the day by using empty plastic milk containers – paint them black and fill with water. Place them around your plants where they will collect heat during the day. Water loses heat more slowly than either soil or air. This collected heat will radiate out throughout the night.
Protecting potted plants
Potted plants are particularly susceptible to frosts because the roots are also unprotected. If you are unable to move your container plants indoors or under cover remember to also wrap the pot in burlap or bubble wrap, or simply bury the pot in soil in addition to protecting the foliage.
If your efforts were too late, or too little to protect your plants from a frost resist the urge to cut off the damaged parts of the plants. To a certain extent, these dead leaves and stems will provide limited insulation from further frost damage. You will have to go back and re-prune your plants in spring anyway.
If you found Protecting plants from frost – quick ways to protect your garden helpful, you’ll find more winter gardening tips on our Gardening channel.
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