Plant Doctor Archive

How can I protect my plants from frost?

I'm worried that some of my plants may succumb to frost this year. How can I protect them?

Cold air is heavier than warm air and flows to the bottom of valleys, where frosts may occur on cold clear nights. It is prudent, therefore, to temporarily remove frost-tender plants from the bottom of slopes or valleys until any risk of frost is over.

There are a number of simple ways to protect plants from frost. For the smaller plant, place a large, transparent glass jar over it, remembering to remove it every now and then to allow for air exchange.

An old coal box with a transparent lid to let in light is also useful.

Alternatively, you can construct a small glasshouse by using bricks as the base (to store warmth from the sun) and covering it with an old window frame.

Frost cloth lets in light and air. Place the cloth over the plant and anchor it down. If you need something in a hurry, you could try using bubble wrap or newspaper as a substitute. Don't leave these on for extended periods of time, however. The bubble wrap will not allow any air through, and the newspaper will eventually turn soggy.

Do not prune or fertilise plants in autumn because new growth will be frost tender. If a plant is frost damaged, leave the damaged parts alone. This will act as a protection to other parts of the plant.

Increase mulch in the soil because this retains moisture, which helps stop frost from forming.

Finally, be prepared. Know your plants, watch the weather and know what to do when the first frost strikes.

Advice by Dr Dan Blanchon from Unitec's Diploma in Sustainable Horticulture and Bachelor of Resource Management.

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