Gardening in the temperate zone

Most Australians garden in the temperate belt, and it is the most forgiving zone in the country: hot enough for warm-climate plants in summer, cool enough for cold-climate plants in winter, and rarely extreme in either direction. That breadth is also its main difficulty. Almost anything will survive here for a while, so gardens accumulate plants with wildly different water needs sitting in the same bed on the same irrigation line.

What defines the temperate zone

Summers are warm to hot and generally dry, with heat waves that arrive as three or four day events rather than sustained months. Winters are cool and wetter, with a clear winter rainfall bias in Perth, Adelaide and much of Victoria, and a more even or summer-leaning distribution around Sydney. Frost is light or absent within a few kilometres of the coast, moderate in inland suburbs, and heavier in valley floors where cold air pools on still nights.

The zone stretches across very different rainfall totals. Perth and Adelaide are dry Mediterranean climates where summer irrigation is essentially compulsory for anything that is not drought adapted. Sydney's Central Coast is far wetter and more humid. Melbourne sits between them, with a reputation for variability that is entirely deserved. Adjust the water-need expectations on this site accordingly: the same plant list runs drier in the west and wetter in the east.

The year in a temperate garden

Autumn, March to May. The prime planting window. Soil is still warm from summer, autumn rain is on the way, and roots establish through winter while the top growth is dormant or slow. Plant shrubs, natives, small trees and perennials. Plant spring-flowering bulbs in March. Sow a green manure crop on empty vegetable beds. Rake and compost fallen leaves rather than binning them — they are the cheapest source of organic matter you will ever have.

Winter, June to August. Prune deciduous trees while fully dormant. Plant bare-rooted deciduous trees and roses through July, which is the last reliable month for bare-rooted stock. Prune roses in July in warmer districts and August in frost-prone ones. Avoid walking on wet lawns and beds; winter compaction is slow and difficult to reverse. Turn the compost heap, which slows right down in cold weather. Sow tomatoes and capsicum in trays indoors in August.

Spring, September to November. Plant hardy vegetable seedlings as the soil warms, and summer crops after your district's last frost. Feed lawns with a slow-release complete fertiliser once growth genuinely resumes, not on the first warm day. Divide summer-flowering perennials. Renew mulch to full depth in October before the dry months. Stake tall perennials early, before they lean. Prune spring-flowering shrubs as soon as they finish, because next year's buds form on the growth that follows.

Summer, December to February. Deep-water established shrubs weekly during dry spells rather than sprinkling daily. Keep the mower blade high. Deep-water anything planted in the last two years. Hold off planting until autumn: a plant put into a temperate garden in January is asking to survive its hardest test with no root system.

Grouping by water need

This is the discipline the temperate zone demands. Because so much grows here, it is easy to end up with a bed containing a Correa that wants no summer water at all, a camellia that wants steady moisture, and a bed of annuals that wants watering three times a week. Whatever you set the controller to, two of the three are wrong — and the low-water plants usually die first, quietly, from root rot rather than drought.

Sort the garden into water zones before you sort it by colour or height. Put the low-water plantings — Correa alba, Westringia fruticosa, Eremophila, Grevillea lanigera, Chrysocephalum, the Dianella and Lomandra species — on the outer, sunnier, drier parts of the block, and leave them off irrigation entirely after the second summer. Put the moderate and regular-water plantings — camellias, Japanese maple, star jasmine, the vegetable beds — close to the house where they are easy to reach and easy to water separately.

Frost pockets and hot walls

Within a temperate block, the difference between the coldest and warmest positions can be three or four degrees on a winter night and ten degrees on a summer afternoon. Cold air behaves like water: it flows downhill and pools against fences, hedges and retaining walls. A low corner enclosed by a solid fence will frost when the rest of the garden does not.

The reverse also applies. A north-facing masonry wall absorbs sun through the day and releases it overnight, which is often enough to carry a frost-sensitive plant such as Alyogyne huegelii or a capsicum through a winter that would otherwise kill it. West-facing walls are the opposite problem: they take late afternoon summer sun at a low angle, and foliage that copes perfectly well elsewhere in the garden will scorch there. Acer palmatum is the classic casualty.

Plants that suit temperate conditions

For structure, Corymbia ficifolia at 8 m by 6 m gives heavy summer flowering on a compact canopy and performs best in the drier southern parts of the zone rather than humid coastal ones. Acacia cognata at 6 m by 5 m makes a graceful weeping lawn specimen, though it is not long-lived. Agonis flexuosa suits coastal positions, with the caveat that its roots run wide and shallow and it should be kept well away from paving. Lagerstroemia indica gives deciduous summer flower and winter sun.

At shrub level the choice is very wide. Westringia fruticosa clips into a formal hedge and survives exposure that kills box. Correa alba handles sand and salt wind. Camellia sasanqua and Buxus microphylla cover the sheltered, better-watered positions. Prostanthera ovalifolia gives a heavy spring flowering in dappled shade but has shallow roots and must not dry out completely. Philotheca myoporoides wants sharp drainage and sulks in heavy clay.

Climbers are straightforward here: Trachelospermum jasminoides is the default evergreen screen at 5 m by 2 m, slow for two years and then dense and easy to keep flat. Pandorea pandorana will cover a full pergola in three years and needs annual thinning to stay off gutters. Rosa banksiae covers a shed wall with almost no thorns, but must be pruned straight after flowering rather than in winter.

Vegetables in the temperate zone

Both seasons work. Cool-season crops — brassicas, peas, carrots, lettuce, silverbeet — go in from March and crop through winter and early spring. Warm-season crops go in after the last frost, which is usually October near the coast and November in frost-prone inland districts. Local observation over two winters gives you a better last-frost date than any published figure.

Soil preparation matters more than variety choice. Add compost to vegetable beds every season, keep 200 mm of workable soil, and mulch between plants once seedlings are established. Water in the morning at the base of plants rather than over the foliage. In the drier western and southern parts of the zone, a drip line under mulch is the difference between a productive summer bed and a daily chore.

Common mistakes in this zone

Mixing water needs in one bed on one irrigation line. The most common design error in Australian gardens, and it is a temperate-zone speciality.

Planting in spring rather than autumn. Spring plantings enter summer with three months of roots; autumn plantings enter it with nine.

Assuming coastal conditions apply inland. Frost in a Melbourne valley suburb is a real constraint, not a technicality.

Watering established low-water natives through summer. They do not need it, and consistently wet roots in warm soil kills them.

Planting a west wall as though it were an east wall. Check where the afternoon sun actually falls in January before committing anything with soft foliage to that position.