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prepare for frost

How To Prepare for Frost

Invest in frost fleece/cloth to cover seedlings and tender vegetables. If a severe frost is predicted it is worth covering everything! Check your weather app daily for frost warnings, and cover the vegetables early in order to trap in warm air.

Frost hardiness: know how crops differ

Lettuce is the least cold-hardy vegetable, even though it grows and tastes better in cooler seasons, and always needs protection from frost. Leafy greens such as Swiss chard, spinach, rocket, parsley and Asian greens can often handle light frost, but you should err on the side of caution. Brassicas such as Brussels sprouts, cabbage and broccoli are good cool-weather crops, and kale handles frost the best. Not only can it survive temperatures below freezing, but these also actually improve its flavour. Root crops such as carrots, turnips, parsnips and beets can survive freezing temperatures, and the taste improves as the plant concentrates more energy on root growth and builds up sugars for frost protection.

Prepare for Frost: Tips for using frost cloth

  • When laying frost cloth, make sure that it doesn’t touch the plants or the plants will burn where it touches.
  • Lift the frost cloth each day so that veggies are exposed to as much light and air as possible.
  • Use 2-litre plastic cool drink bottles (with the base removed) as cloches to protect small seedlings (and lettuce) from the cold. Leave off the cap so that air can circulate.

Good to know

In all cases, open the lid during the day to let the air circulate, and close it again late in the afternoon to trap the day’s warmth inside. This prevents too much heat from building up.

Prepare for Frost: Keep plants warm

Tender leafy crops, and even those that stand still over winter like spinach, cabbage and beetroot, will grow better if they are protected from frost as well as from cold wind and draughts. Make a mini greenhouse. This is a small plastic tunnel made by bending wire into hoops and covering it with plastic sheeting. Bury the edge of the plastic in soil to secure it. The aim is to moderate the very low night temperatures by letting the sun warm up the soil during the day. Build a cold frame.

A good winter project for DIY gardeners, the traditional cold frame is a bottomless wooden box (made from recycled pallets or crates), covered by a glass or plastic lid that is hinged for raising during the day. It can be placed over veggies in the garden or used for protecting veggies in pots or seedling trays.

Mustards like mizuna and tatsoi as well as garden cress, leafy veggies like lettuce, baby spinach and even herbs like rocket and coriander can be grown as mini- or micro-greens in a cold frame.

Recycle and repurpose items such as discarded bricks, concrete blocks, old windows and glass refrigerator shelves to make an instant cold frame. For instance, make a frame of bricks with two panes of glass on top or place bales of hay around a bed and lay an old window across the top.

Winter watering do’s and don’ts

  • Water during the warmest time of the day and avoid wetting the leaves.
  • Keep soil consistently moist, especially for lettuce, which develops a bitter taste if the soil dries out.
  • Over-watering results in cold, wet soil that encourages damping off while under-watering stresses plants, making them less resilient to frost.
  • Ease up on watering if a cold front is predicted, but don’t let the soil dry out completely.
  • In winter-rainfall areas, raised beds will ensure good drainage and warm up more quickly in spring. Fertiliser requirements Although growth is slower in winter, feeding seedlings with a liquid fertiliser or plant tonic like kelp or fish emulsion strengthens them to resist the cold. Brassicas have high nutrient demands and will benefit from regular applications of nitrogen-rich fertiliser. When garden peas and broad beans start flowering, feed them weekly with a liquid fertiliser.
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