When to plant in Australia: season by season

Ask ten Australian gardeners when to plant and you will get a firm answer and no agreement. Timing matters far more in some districts than others: a month either way is close to irrelevant at Coffs Harbour, and decides the whole first year on the tablelands.

Why autumn usually wins

In most of Australia, autumn is the season to aim for. Not because of rain, which is unreliable, but because of soil temperature. Roots grow whenever the soil is warm, and after summer the ground holds its heat for months while the air above it cools. A plant put in during March or April builds roots through autumn and early winter with almost no demand from the foliage above.

By the time the first real summer heat arrives, that plant has had six months of root growth. A spring planting gets perhaps eight weeks, and has to push new leaves at the same time. That is the entire argument, and it holds across climate zones.

Roots on most woody plants keep working while the top 300mm of soil holds above roughly 10C, and that layer cools long after the air does. Through Brisbane and along the Sydney coast it stays above 15C into June; around Orange or the Southern Highlands it has fallen through 10C by early May. So autumn is not one set of dates. In Brisbane the window runs March to June. On the tablelands it closes in mid April.

Season by season

Autumn (March to May) is the default for almost everything: trees, shrubs, hedging, screening and natives. Mass plantings benefit most, since they are the ones you cannot hand water. A border of Westringia or a boundary run of Callistemon Eureka put in during March has its roots out of the potting mix before the first frost, and asks very little over winter.

Winter (June to August) works well in warm and temperate districts. Bare-root stock has to go in now, since it is lifted dormant. Almost everything here is container grown, which removes that deadline, but winter still suits anything deciduous: a Katsura Tree or a Packham Triumph pear moved while it is leafless has nothing above ground making demands on the roots. In cold gardens, leave frost-tender species until early spring.

Spring (September to November) is the next window, and the necessary one for frost-tender and tropical plants: frangipani, heliconia, most tropical foliage and cordyline ti plants prefer to go in as the soil warms. Palms belong in that group. A Majesty Palm barely moves a root until the soil is up around 18C, so an April planting sits idle for five months while the crown keeps transpiring. Citrus behave the same way in cold gardens: a Lemonicious lemon headed for Ballarat should wait for October. Spring plantings need real watering discipline through the first summer.

Summer (December to February) is the season to avoid where you can, but it is entirely possible with container stock, which is what almost everything here is. It costs more attention; the method is below. Brachychiton rupestris stores water in its own trunk and transplants more easily than most large trees, which is why you see them moved in weather that would finish anything else.

The planting calendar at a glance

Adjust for where you are

Subtropical Queensland and the Northern Rivers

The wet season drives everything. Brisbane, the Sunshine Coast and the Northern Rivers take most of their rain between November and March, and the trap is planting into the middle of it rather than at either end. Ground wet for a fortnight holds no air, and a fresh root ball sitting in it is how phytophthora starts. Late February through April is the dependable run: storms eased, soil still warm, humidity keeping leaf stress low while the roots move.

Perth, Adelaide and the dry-summer south

In Mediterranean climates autumn is emphatically the answer, because planting into the dry season means hand watering through five months of heat. The calcareous sand behind the Perth coast sharpens that: water moves through it faster than a small root ball can take it up, and a 140mm plant put in during November can be dry by the following afternoon even on a daily dripper. Wait for the break, usually late April or May. Adelaide runs the same calendar on heavier ground: the plains clay holds moisture far longer, which helps in February and becomes a drainage question by July.

Melbourne, Geelong and the basalt clay

The basalt country through Melbourne's west, out past Werribee and Sunbury, seals up over winter and water sits on the surface. Autumn planting there means March or early April, while the ground still drains, rather than late May. Miss that and September is safer, because grey-leaved Mediterranean plants sitting in cold saturated clay from June to August rot instead of rooting. A Swan Hill olive is the clearest case: its own page names wet feet as the thing it will not forgive. If soil is the real problem, see planting into clay.

Canberra, the tablelands and the ranges

Autumn works for hardy stock here if it is in by mid April. Later than that, evergreens wait for spring, where our frost tolerant plants guide sends cold-district plantings: a small root system dries out in its first winter more often than it freezes. Dormant deciduous and bare-root stock still goes in over winter. What catches people in spring is late frost on soft new growth through September and October, which still arrives in Canberra, Orange and Armidale. Magnolia Elizabeth shows the split: the tree takes the cold without trouble, while a late frost will brown flowers already open.

Pot size changes the window you can use

The smaller the pot, the faster it dries out. A 140mm pot holds about 1.5 litres of mix; a 200mm around 4.4, a 300mm about 15, a 400mm roughly 35. Volume climbs cubically, so the step from 200mm to 400mm changes behaviour far more than the labels suggest.

What that volume buys is drying time. In a Riverina January a 140mm root ball can go from soaked to bone dry between breakfast and dinner. A 45L will not. Book small stock for autumn, when a missed watering costs nothing. Advanced trees want the cooler half of the year too: the root ball is small against the canopy above it, so a big tree is the one most likely to fail in a hot first summer, not the least. What advanced trees actually means covers handling; low water gardens gives litres per soak.

Which plants actually care about the month

Most evergreen shrubs are close to indifferent. Three groups are not.

• Deciduous trees and deciduous fruit. Winter, while the plant is leafless and dormant, is when it moves with the least stress. Both the pears and the deciduous magnolias prefer to move bare of leaf.
• Camellias. These split by district, and the Camellia japonica Ecclesfield page puts it plainly: autumn where winters are mild, spring where they are cold, with water kept up through the first two summers.
• Anything that will not take wet feet. Olives, banksias, most grevilleas. Pick the season around how wet the ground will be, and mound the bed if drainage is doubtful.

Planting outside the window on purpose

Sometimes there is no choice: a house settles in December, a builder finishes in January, stock arrives when it arrives. Four things change.

• Soak the root ball before it goes in, standing the pot in a tub until the bubbles stop. Dry potting mix repels water; anything poured on afterwards runs around the outside.
• Plant in the last hour of daylight, then shade it for a fortnight: shade cloth on star pickets, a market umbrella, anything that takes the middle of the day off the foliage.
• Mulch 75mm deep across the root zone, clear of the trunk. Bare soil in a Mildura February kills surface roots outright.
• Skip the fertiliser, and water onto the root ball itself every second day for a fortnight, then twice a week.

What goes wrong

Planted in autumn, dead by August. Nearly always drainage. The plant went into ground that then stayed cold and wet for three months, and the roots drowned before they grew. The date was fine. The hole was the problem.

Planted in spring, dead by February. Nearly always water, and nearly always the root ball rather than the bed. Ten weeks of root growth does not reach past the edge of the old pot, so the soil around it can be damp while the plant dies of thirst.

It has not shot, so it must be dead. Deciduous plants break at very different times, and some are genuinely late. Diamonds in the Dark is described on its own page as deciduous with a late spring leaf break, so a bare crepe myrtle in October, in a garden where the maples leafed out six weeks ago, is normal. Scratch a twig. Green under the bark means wait.

The frost got it. It got the new growth. A hardy plant hit by a September frost sheds the soft tips and pushes again behind them. Leave the damage on until the frosts have finished, because it shelters the buds underneath.

What matters more than timing

Three things outrank the calendar. Water deep and infrequent, so roots go down rather than sitting in the top 50mm. Mulch over the root zone, clear of the trunk. And plant at the right depth, the top of the root ball level with the soil around it. A plant put in badly in perfect autumn conditions does worse than one put in well in January.

For the full method on larger stock, see planting and establishing advanced trees. Ready to plant? Start with the full range, or go straight to hedging, screening and feature trees. Every order ships farm-direct with flat $99 delivery in QLD, NSW, VIC, SA, ACT and WA, a $399 minimum order, and the 30-Day Healthy Plant Guarantee.

Related ranges: Flowering cherries and blossom trees, Crabapples.

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