Botany

Australian Native Shrubs Suited to Heavy Soils



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With increasing restrictions on water usage in most Australian states, gardeners are having to reconsider their options when it comes to plants.

Plants endemic to an area should thrive with little or no extra attention. Whatever care, added water and nutrients come their way should only enhance their natural features. Thus natives are becoming more and more popular in suburban gardens and parks.

Australia is a large continent with a variety of soil types so not all natives do well in all areas. Plants that do well in heavy soils will not necessarily do well in lighter sandy soils. Clay soil consists of very fine particles which can set hard when dry, causing damage to the roots of the plants. Heavy soil can be improved by the addition of organic material such as peat moss, compost or leaf litter, or commercial gypsum (hydrated calcium sulphate).

The following are some of the medium sized shrubs (up to 4 metres) endemic to Australia which are well suited to heavy soils. The minimum height to be expected is given in each case.

Acacia decora (2m) is also known as the Western Silver Wattle and is endemic to Queensland, New South Wales and Victoria. It responds well to regular light pruning. The phyllodes (modified leaf stalks) are 2-5cm long, leathery and grey-green. The plant produces terminal racemes of golden flower heads from August to October. The Acacia decora is adaptable to very wide range of well-drained positions. It is not affected by frost.

Banksia spinulosa (6m) is also known as the Hairpin Banksia and is native to Queensland, New South Wales and Victoria. The dwarf form reaches 1-2 metres. The serrated leaves grow to 8cm long. It flowers from March to August. The flowers can be yellow or amber with black or red styles. It is a hardy plant suited to most well-drained acid soils.  It is another that is not affected by frost.

Callistemon ‘Burgundy’ (4m) is a cultivar. It has deep red to burgundy bottlebrushes of 8 to 10cm long. These are produced from September to December and sometimes also in March and April. It is a selected seedling of C. ‘Reeves Pink’. It is hardy to a range of conditions and responds well to pruning.

Callistemon ‘Reeves Pink’ (4m) is another cultivar. The pink bottlebrush flowers are tipped with gold. They grow 8 to 10cm long. The flowers are produced from October to December and sometimes also in March/April. It is a selected seedling of Callistemon citrinus. All Callistemon cultivars and forms are commonly propagated from cuttings to retain the characteristics of the parent plant. Variations can occur if new plants are grown from seed.

Callistemon viridiflorus (3m) is also known as the Green Bottlebrush. It is a native of Tasmania. It has a fairly upright habit with yellow-green brushes mainly from November to January. It grows well in moist or even temporarily water-logged conditions and is not bothered by frost.

The grevillea ‘Clearview David’ (3m) is a cultivar. It is a bushy shrub with narrow, dark green, prickly leaves. The striking flowers are a vivid red with white, and are produced in clusters from July to November. It is a hardy plant which can be grown in a range of well-drained positions. It responds well to pruning and is not affected by frost.

Another good grevillea for heavy soils is ‘Poorinda Firebird’ (3m). This showy cultivar has clusters of bright red flowers mainly from June to December. It is a hardy hybrid suited to most well-drained positions. It responds well to pruning and is not affected by frost.

Hakea nodosa (3m) is also known as the Yellow Hakea. It often has an upright habit but some will spread. The leaves are narrow and pine-like. Fragrant yellow flowers appear mainly from February to May. The yellow hakea will tolerate moist to wet conditions.

Leptospermum nitidum or ‘Copper Sheen’ (2.5m) is a cultivar. The foliage is reddish with bright, deep red new growth. The lime-yellow flowers are around 2.5cm diameter and appear from September to November. Although worthy of cultivation for the foliage alone, the flowers are also attractive. Pruning will help promote new growth.

Melaleuca incana (2m) also goes by the name of Grey Honey-myrtle and is endemic to Western Australia. It is an attractive plant with grey-green, pendulous foliage. Pale yellow brushes up to 3cm long appear from September to December. It is suited to moist or well-drained positions.

This is just a small sample of the choices that you have when establishing a garden in an area of heavy soil.  Your local garden centre will be able to suggest many more colourful and water-wise native plants.

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