Frost

By Hannah Moloney and Sarah Pickering

Winter is here and as the temperatures drop in most parts, gardeners are gearing up to protect their plants from the icy grip of frost.

Frost occurs when temperatures fall below 0°C at night and moisture in the air or ground turns into ice. Still nights with clear skies and low humidity can often be a recipe for frost. As for frost damage, it happens when the water stored inside plant tissues and cells freeze.

Frost warnings are categorised as light, moderate or heavy, which refers to how cold it will get, and how severe the damage could be.

So, what can you do about frost?

Gardening Australia's Hannah Moloney helps us understand frost and shares some practical solutions to keep the garden protected.

In cooler parts of Australia frost-hardy crops include broad beans, garlic, spring onion and different types of brassicas.

Perennials such as artichokes and deciduous fruit trees are also quite tolerant of frosts.

Generally, younger leaves on seedlings and new growth are less tolerant.

In most of Tasmania and the Alpine regions of New South Wales and Victoria, frosts can happen well into spring. Compared to more temperate regions, there are different planting schedules and methods to avoid losses.

In Tasmania, if you plant tomato seedlings out in the garden in September, they could be completely wiped out after one cold night.

Hannah suggests cool-climate gardeners wait another month until around late October or early November before starting frost-sensitive "spring planting".

A practical way to protect your plants is to make use of microclimates. Shelter less hardy species under a tree canopy or plant on higher, warmer points in the garden as frosts are often worse in low-lying areas.

It may seem contradictory to add more water, but a healthier plant, that isn't drought-stressed when frost hits, is more likely to survive.

Also, more water in the soil means more warmth in the soil, so it will take longer to freeze.

Leave soil uncovered and wait to mulch until frosts are over. Darker coloured soil can soak up the sun and retain more heat at night, so it is less likely to get as cold.

Even frost-hardy plants can benefit from protection. Cover plants overnight with cardboard boxes or bed sheets.

When using fabric, Hannah suggests propping it up with plastic pots to protect plants from the weight of the sheet, and to anchor edges down with rocks. In areas with prolonged frost exposure, consider something semi-permanent.

Hannah uses poly-pipe to create a dome over the bed, which can be covered with shade cloth or plastic. Seedlings grown in a greenhouse or cold frame can be transplanted outside after the last risk of frost. Wildlife-safe netting over fruits trees also works a treat.

Frosts aren't all bad. Low temperatures can kill or slow pests and pathogens, which means you get a break from having to deal with them.

Some plants thrive in cold conditions, and you can too, by getting to know your region's climate and using the right protection and growing methods for your garden.

Watch this episode of Gardening Australia on the website or on ABC iview.

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