Getting a tropical look in cooler Australian districts

The look you are chasing was photographed somewhere warm, and you are gardening somewhere that gets frost on the lawn in July. That gap is worth being honest about before you spend anything, because plants in this group rarely fail for the reason people expect. One cold night accounts for very few losses. Six weeks of cold soil that never drains accounts for a great many, along with dry wind pulling moisture out of large soft leaves faster than chilled roots can replace it, and a position in the middle of an open lawn when a warm brick wall a few steps away would have carried the plant through.

A convincing tropical garden in Canberra, Armidale, Orange, the Adelaide Hills or the lower Blue Mountains is mostly a siting and drainage exercise. Get the site right and a fairly ordinary plant list will read as tropical. Get it wrong and even a well-chosen plant from the tropical plants range will still sulk.

Find the warm pocket before you choose anything

A single block can carry more than one growing climate across it. The north-facing side of a brick or rendered wall absorbs sun all day and gives it back overnight, and the strip within a metre or so of that wall runs warmer and drier than the open yard. Add eaves overhead and you have removed much of the radiant frost risk as well, because frost settles hardest on surfaces with a clear view of open sky.

Cold air behaves like water. It drains downhill overnight and pools against fences, hedges and retaining walls at the bottom of a slope. Whichever way your block falls, that low corner is the frost trap, colder again if the slope faces south, and the ground near the house is where tender material belongs.

Wind does more visible damage than cold in most cool districts. Large paddle leaves shred, and winter wind dries foliage while the root zone is too cold to replace the water. Something evergreen and tough on the windward side, planted a season ahead of the tropical material, is not optional. The low maintenance and feature trees ranges are where that shelter layer comes from.

Winter wet plus cold, not cold alone

Almost everything in this group evolved with warm wet summers and drier winters. A cool Australian garden often hands it the reverse: a dry summer and a cold, sodden winter. Roots sitting in cold water cannot take up oxygen, rot follows, and the plant collapses in the first warm week of spring while the owner blames the frost.

So mound. Plant into a raised bed or a broad low mound of coarse improved soil sitting proud of the surrounding grade, so water can leave sideways. Do not dig a neat hole in clay and backfill it with potting mix, because that is a bathtub. Composted bark and aged manure worked through a wide area beats a rich hole every time. Do not try to fix clay with a little gravel or sand mixed through it, which sets harder than the clay you started with, and use gypsum instead where the clay is dispersive. Keep mulch thick across the bed but pull it back clear of crowns and stems.

Then stop pushing growth from late summer. Nitrogen in March produces soft new leaves that meet the first frost half grown. Ease off watering as autumn cools, and never water a cold soil that is already damp.

Building the look in three layers

The tropical effect comes from layering and leaf size, not from any single species. Three storeys, planted close, with almost no bare mulch showing by the second season.

Canopy

Giant Bird of Paradise (Strelitzia nicolai) does most of the overhead work in a cool garden. It is a clumping structure rather than a tree, it holds its shape in a courtyard, and it runs from small pots up to 200L if you want scale on day one. Foliage marks in frost and tears in wind, so give it a wall. Leopard tree (Caesalpinia ferrea) is the other useful overhead option and drops its leaves in winter, which lets low sun into the bed underneath; young trees need frost protection for the first few years. Cottonwood hibiscus (Hibiscus tiliaceus) has the heart-shaped leaf and coastal toughness, but it wants a frost-free position.

Mid-storey

Cycads carry the look through winter when the soft-leaved plants look shabby. Sago palm (Cycas revoluta) comes from southern Japan and takes cold far better than its appearance suggests. It is also poisonous, the seeds worst of all, so think again in a yard where a dog digs. Pineapple zamia (Lepidozamia peroffskyana) is an east-coast Australian rainforest cycad and copes with cool shaded positions. Add variegated shell ginger (Alpinia zerumbet Variegata) for striped cane foliage; frost burns the tops, but the rhizome reshoots in spring where drainage is right. Tibouchina Alstonville brings the purple autumn flush and is grown well south of the subtropics, though soft new growth is frost sensitive.

Floor

Philodendron Xanadu is the usual groundcover for this style, set roughly 800mm to a metre apart. It is not frost hardy, so it only works under a canopy that blocks radiant frost, and in the coldest districts it belongs in a pot. Alocasia wentii is the smaller elephant ear and retreats underground in a cold winter rather than dying outright. Cordyline australis Red Star and the wider cordyline range supply vertical strap foliage; the australis types from New Zealand are genuinely frost hardy, while the fruticosa Ti plants are not. Ferns fill shaded gaps and read as rainforest floor.

Which ones take light frost, and which will not

Light frost once established and sited well: Cordyline australis forms including Red Star and Torbay Dazzler, Cycas revoluta, Lepidozamia peroffskyana, Dioon edule, Zamia furfuracea in a dry sheltered spot, Strelitzia reginae, and Tibouchina Alstonville. The word established is doing real work in that sentence. A first-winter plant out of a 140mm pot is not the same animal as a settled clump three years in.

Dormant or deciduous in winter, which is normal rather than a failure: frangipani (Plumeria) drops its leaves and wants a dry winter, canna dies back to the rhizome, and Alocasia disappears underground and returns.

Must be frost free, or must live in a pot that comes under cover: Cordyline fruticosa Ti plants, croton (Codiaeum variegatum), heliconia, Calathea lutea, Monstera deliciosa, philodendrons including Xanadu in the open, and Hibiscus tiliaceus. In a cool district these are container or indoor plants that spend summer outside, which is a sound way to run them.

When not to buy from this group

Say no if the only position you have is an open, exposed, south-facing yard on heavy clay at the bottom of a slope. Nothing here will thank you and you will replant twice. Say no if you need screening you can rely on year round in a frosty district, because burnt foliage in August is not a screen; use privacy screening for the structure and treat tropical material as accent planting inside it.

Say no if you cannot water through the first two summers; these plants are lush because they transpire hard. Say no to large-format sizes in an untested position; buy one, watch it through a winter, then commit. And say no if what you really want is a garden that looks after itself, which is a different brief served better by natives.

Getting them through the first winter

Plant in spring or early summer in a cool district. Autumn planting gives the root system no warm weeks to settle before it has to sit through cold wet soil, and that is where most losses come from. There is more on timing in when to plant trees and shrubs in Australia.

For the first two winters, treat everything as one grade more tender than the label suggests. A hessian screen on the windward side, a temporary frame with shadecloth over the top on clear still nights, mulch kept off the stem, and no fertiliser after February. Frost damage on cycads and cordylines looks alarming and is usually cosmetic, so resist cutting the damaged foliage away until spring, because those tatty leaves shelter the crown underneath. If you are weighing winter structure against how much bare stem you can live with, evergreen or deciduous is worth reading alongside this.

Pots solve the hard cases. A large container on castors near a north wall gives you a warm, free-draining position you control, plus the option to wheel the plant into a garage for a fortnight of hard frosts. Frangipani, Ti plants and monstera all run this way for years. Use a coarse open mix, and raise the pot on feet so the drainage holes never sit in a saucer of water.

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