Native Australian plants for a wildlife refuge in extreme heat
On a 40 degree day wildlife has the same problem as people: it needs somewhere cooler to escape to. A well-planted garden can supply what animals seek for refuge: shade, dense cover, a cool ground layer and water.
Plants cool a garden in measurable ways. In a study of backyards in western Adelaide during a heatwave, vegetation lowered surface temperatures by up to 5 to 6°C compared with non-vegetated land. Trees, shrubs, grasses and leaf litter each add a layer to that cooling. This guide covers the habitat heroes that can help gardeners in eastern and south-eastern Australia build a shaded refuge for wildlife.
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Plants for each layer
Shade above
Overhead foliage blocks direct sun reaching the ground. A tree or large shrub also gives birds and possums somewhere to rest through the hottest hours.
Drooping sheoak (Allocasuarina verticillata)
Drooping sheoak is an evergreen, small to medium tree with fine, needle-like branchlets that hang in curtains. Cockatoos eat the seeds, including the threatened glossy black-cockatoo and insect-eating birds forage in the foliage. It is hardy and tolerates drought, heavy frost, wind and salt.
It is moderately slow-growing and young plants are palatable to rabbits and livestock, so protect them until they are established. The fine litter it drops builds a ground layer beneath the tree, though it can limit what grows below.
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Sweet bursaria (Bursaria spinosa)
Sweet bursaria is a dense shrub with glossy dark green leaves. Its species name, spinosa, is Latin for prickly. In a heatwave, its cover keeps small birds shaded and it gives them protected places to nest. In summer, it carries masses of scented white flowers that attract butterflies and other insects, and bronze seed capsules follow through winter.
It suits full sun to part shade and a range of soils from clay to sand. It tolerates dry conditions and frost once established. Prune it lightly each year with sharp pruning tools to stop it becoming leggy.
Dense shelter
Many of the best shelter shrubs are prickly for a reason. Spines and sharp leaf tips are a common plant defence against browsing animals. Small birds have turned that defence to their advantage by sheltering deep inside thorny growth. Finches even gather spider webs from bursaria foliage to bind their nests.
Prickly tea-tree (Leptospermum continentale)
Prickly tea-tree is an upright, rigid shrub with stiff, sharp-tipped leaves. Planted in a group, it forms a dense thicket that makes an excellent refuge. Masses of white flowers cover the stems in spring and summer and provide pollen and nectar for butterflies and moths.
R.W. Purdie, CC BY 3.0 AU, via Wikimedia Commons
It is hardy and tolerates frost and long dry spells, so the thicket holds its cover through a dry summer. It also copes with poorly drained sites. A light prune after flowering with sharp secateurs keeps it dense. For more options in this role, see our guide to screening and privacy.
Juniper wattle (Acacia ulicifolia)
Juniper wattle is a small, spreading to upright shrub with rigid, sharp-pointed foliage. Pale cream flowers appear from autumn into spring and supply pollen for native insects and nectar for honeyeaters, and the seed feeds parrots and native pigeons. It grows fast, so it gives low cover quickly, which helps when you are planting ahead of summer.
It is hardy and frost tolerant but short-lived, so plan to replace it after some years. It is also sold as prickly Moses, a name shared with another wattle (Acacia verticillata). Wear thorn-proof gloves when planting and pruning.
Native rosemary (Westringia fruticosa)
Native rosemary forms a dense, rounded shrub with narrow grey-green leaves, which make it a reliable refuge for small birds in hot weather. White to mauve flowers appear mainly in spring and summer and often on and off through the rest of the year.
It grows in full sun or part shade and tolerates drought, frost, wind and salt spray, so it copes with hot, exposed sites. Prune it after flowering with sharp snips to keep it dense. Our guide to native garden plants with high wildlife value has the full profile and care notes.
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Plant three, not one
A single prickly shrub gives cover, but three planted close together knit into a thicket that small birds can slip into and use as a shaded hideout. Set them in the middle of a bed rather than beside a path, because they are sharp by design.
Cool ground layer
Reptiles, frogs and invertebrates spend the hottest hours at ground level. In South Australian bushland, daytime temperatures in leaf litter averaged 1 to 5°C cooler than the surrounding ground and humidity was up to 28 per cent higher.
Grass tree (Xanthorrhoea glauca)
The skirt of dead leaves around a grass tree is one of the best-measured heat refuges in the Australian flora. In a later study of the South Australian grass tree (Xanthorrhoea semiplana), conditions inside the skirt were up to 20°C cooler than the air outside on hot summer days.
It grows only 1 to 2cm a year, so patience is required. Plant it in full sun in well-drained, low-nutrient soil with a sturdy spade and resist the urge to feed it. A mature plant is the perfect feature in a bush-style garden.
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Common tussock-grass (Poa labillardierei)
Common tussock-grass forms dense, arching clumps that shade the soil at the base. Small ground-dwelling animals use that cover, and the leaves feed the caterpillars of several native butterflies.
Leave the clumps unclipped through summer so the base keeps its shade and shear them back hard in late winter to refresh them. Seedlings need moist soil to establish, so water well through the first summer.
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Lomandra (Lomandra longifolia)
Lomandra handles shade, heavy clay and dry ridge soil and is very drought tolerant once established. That makes it a practical ground-layer plant beside hot paving and walls, where few plants hold a dense cover.
The clumps shade the soil at the base and give lizards and invertebrates somewhere to retreat. They also feed the caterpillars of native butterflies and moths. Clumps can be divided with a garden fork or hori hori to make more plants.
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Tall sedge (Carex appressa)
Tall sedge forms dense, bright green tufts that spread slowly from short underground stems. It grows naturally along wetland and stream margins, which makes it a good fit for the edge of a pond or a low damp spot. Birds nest and shelter in it, frogs use it as habitat and its leaves feed the caterpillars of native butterflies.
John Tann from Sydney, Australia, CC BY 2.0, via Wikimedia Commons
It tolerates full sun or part shade, some drying out and frost. The leaf edges and flower stems are sharp enough to cut, so wear gloves when cutting it back.
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Start small
Plants do most of the work, but a few elements make a real difference to heat-stressed wildlife and none needs special equipment.
Put out a bowl of water
A kitchen bowl, a plant saucer or an old baking dish works well. Keep it shallow, put it in the shade and add a few stones or sticks so small animals can climb out. Water ties the layers together and keeps the humidity up for frogs and skinks.
Leave the litter
Fallen leaves, logs and branches under trees and shrubs support the cool ground layer, so leave them in place. Dense foliage is the refuge, so avoid heavy trimming as well.
A fact about shade
In a study of 471 trees across Greater Sydney, researchers measured the ground between noon and 3pm on summer days. Shade cut the surface temperature of bare soil by an average of 22°C and of bark mulch by almost 25°C.
Plant the future shade
If you have the room, plant a tree where it will shade the ground through the hottest part of the afternoon. Water new saplings well through their first summer as they establish strong root systems.
Mist the foliage
When a heatwave is forecast, a mist from the hose into trees and shrubs, ideally in the shade, creates cooler pockets for animals to use.
It is very simple to add these elements to a garden, and it goes a long way for the wildlife that has nowhere else to turn in extreme heat. Even one shaded, sheltered corner gives local animals somewhere to get through the hottest days.
keep reading
A Guide to Australian Native Gardening
How to plan, plant and care for a thriving native garden, whatever your experience level.
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