Cool and mountain Australia: frost, rain and what to plant when

Frost and rain

Cool and mountain Australia takes in Tasmania, the Northern and Southern Tablelands of New South Wales and the Australian Capital Territory. Summers are mild or warm and winters are cold, with frost that runs on well into spring. For a gardener the hard edge of the year is not midwinter but the weeks after it, because a warm September can tempt tender plants out just before a late frost. The growing season is shorter than on the coast, and the tomatoes go in last.

Frost

BoM maps show that potential frost days in Australia are mainly confined to the period from late autumn to early spring, and that the risk increases with elevation. In this zone, BoM and CSIRO give the end of the frost risk, from records for 1989 to 2018, as the second week of October at Glen Innes, about 20 October at Armidale and the last week of October at Canberra, Goulburn and Yass. Frost nights have been recorded as late as the last week of November on the tablelands, and Canberra’s latest was 27 December 2018. No equivalent set of first-frost dates is published, so the start of the season is best taken as late autumn.

Tasmania is milder on the coast and harsher inland. Hobart averaged about nine likely frost days a year in 1989 to 2018, down from 11 before that, while Launceston averaged 73, and inland in the north frost nights have been recorded in every month.

Frost forms on clear, calm nights, and cold air pools in low ground, so valley floors and frost hollows are the worst places for tender plants. Cover them before dusk with fleece or hessian, and uncover them in the morning. The reports also find more frost nights after a dry winter and spring: about three more at Canberra, five more on the Northern Tablelands and 12 more in South East NSW.

Rain and watering

Rain falls through the year. Annual totals are about 830 mm for the ACT, 860 mm on the Northern Tablelands, 800 mm in South East NSW, 1,180 mm in southern Tasmania and 940 mm in northern Tasmania, all from records for 1989 to 2018. BoM and CSIRO describe summer rain as the reliable season on the Northern Tablelands and spring as reliable in the ACT, while winter rain is unreliable on the Northern Tablelands.

Autumn is the least reliable season in the ACT and South East NSW, so water new plantings and bulbs if the rain does not come. A dry winter is the cue to keep frost cover ready. In the house, the cold season means heating, so keep plants away from radiators and from cold glass, and water less often as growth slows.

Month by month

Each month below adds the local timing to the matching southern hemisphere page, which has the general list.

January

Midsummer. Sow beetroot, carrots, leeks, lettuce, silverbeet, parsnip and turnips, and plant out the autumn brassicas. Water deeply and mulch. The general list is on January, south of the equator.

February

Late summer, and the start of the winter sowing. Sow kale, leeks, kohlrabi, lettuce, silverbeet, carrots and turnips, and take cuttings of lavender and pelargonium. Divide perennials while the soil is still warm. The general list is on February, south of the equator.

March

Autumn. Sow broad beans, cabbage, cauliflower, carrots, leeks, onions, parsnips, spinach and radish, and plant spring bulbs while the soil is still warm. The general list is on March, south of the equator.

April

The nights cool quickly, and frost is close on the high ground. Plant garlic, onion sets and shallots, plant asparagus crowns, and sow peas, broad beans, spinach and lettuce. Bring tender pots under cover. The general list is on April, south of the equator.

May

Frost is arriving, in late autumn. Plant garlic, sow broad beans and peas, and mulch against the cold. Plant hardy perennials so the roots can settle through winter. The general list is on May, south of the equator.

June

Winter, with frosts inland. Prepare planting holes for bare-root roses and apples, plant dormant blackcurrants, raspberries and rhubarb as they arrive, and plant shallots and broad beans. Leave frost-damaged growth in place. The general list is on June, south of the equator.

July

The coldest month. Prune roses, fruit trees and vines, and keep planting bare-root stock. Plant garlic and shallots, and keep fleece within reach. The general list is on July, south of the equator.

August

Late winter, with the frost still not finished. Chit seed potatoes in a cool, light place, ready to plant once the frosts are easing. Sow peas, onions and kohlrabi, and plant garlic and shallots if they are not yet in. The general list is on August, south of the equator.

September

Spring, and the temptation month. Sow beetroot, carrots, lettuce, parsnips, peas, radish and silverbeet, and start tomatoes, peppers and basil under cover. Do not plant out the tender crops yet, and plant potatoes in sheltered ground. The general list is on September, south of the equator.

October

The frost risk ends between the second and last weeks of the month on the tablelands and in Canberra. Plant dahlias and the summer annuals once the last frost has passed. Harden off tomatoes, peppers and cucumbers, and keep fleece nearby. The general list is on October, south of the equator.

November

Plant out tomatoes, peppers, beans, cucumbers, courgettes and sweet corn, but keep fleece handy until the end of the month, because frost has come in the last week. Mulch and water deeply. The general list is on November, south of the equator.

December

Early summer. Sow parsnips, kale, turnips and Brussels sprouts for the winter, and keep the summer crops watered. Stake tall plants. The general list is on December, south of the equator.

Plants that belong here

• Apple is planted bare root in the dormant season and the entry gives a minimum of -25 °C.
• Raspberry canes are sold bare root through the dormant season and should go in as soon as they arrive.
• Blackcurrant is planted bare root and deliberately deep, so that buds below the soil make new shoots from the base.
• Rhubarb is bought as a dormant crown and planted through the cold months.
• Garlic needs a cold period to split into cloves, so an autumn planting matters more than a spring one.
• Kale stands through frost and snow, and the flavour improves after a hard frost.
• Potato is planted deep once the frosts are ending and earthed up as it grows.
• Daffodil is planted early in autumn, and its leaves are left alone after flowering.
• Rose is lifted dormant and planted bare root through winter.

Questions from the margin

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