Native Australian Trees Suited to Heavy Soils

Australian gardeners are becoming inured to facing more severe water restrictions with each passing year. Many are turning to native species, each of which flourishes in its local area with little or no outside assistance. The type of soil dictates to a degree which natives will thrive in that area. Clay and clay-loam soils are not suited to all natives but such soils can be improved by the addition of organic material such as peat moss, compost or leaf litter. Gypsum (hydrated calcium sulphate) is also very beneficial and causes the fine particles to join together allowing better penetration of moisture and improved aeration of the soil. Gypsum should always be applied to damp soil.

The following are examples of Australian native tall shrubs and trees which are well suited to heavy, clay-type soils. Most of the species below will do well in lighter land too but these in particular will cope with heavier soils.  The minimum height is given in each case.

Acacia acuminata (5m) is also known as Raspberry Jam Wood as the freshly cut wood smells like raspberry jam. It is endemic to Western Australia. It is a quick-growing, small tree with narrow foliage. Bright yellow, rod-like flower-heads are produced from July to October. It likes well-drained soils and a sunny position. It is not affected by frosts.

Acacia retinodes (5m), also known as Wirilda, can be variable in form with broad or narrow phyllodes (modified leaf stalks) and weeping foliage on some forms. Lemon-yellow flowers appear mainly from November to May but may be seen throughout the year. It is a quick-growing small tree and resistant to frost.

Allocasuarina littoralis (4m) or Black She-oak is a slender tree with fine foliage. Rusty brown, male flower spikes are produced from March to May. It is adaptable to a wide range of well-drained situations. It is suited to exposed coastal conditions and not affected by frost.

Brachychiton acerifolius (40m), also known as the ‘Flame Tree’ is native to Queensland and New South Wales. It is a rainforest tree which generally doesn’t grow as big in cooler areas. It may have a very profuse display of dull pink to red, bell-shaped flowers from November to March. The flowers are followed by brown, woody fruits from 7 to 12cm long.

Eucalyptus astringens, or Brown Mallet, is an upright to spreading tree which grows to 25m. Endemic to Western Australia it was once harvested for its tannin content. It has a prolific display of cream-yellow flowers mainly from October and November. It prefers a well-drained sunny position. The brown mallet is also popular with bird species.

Eucalyptus maculata, or Spotted Gum, is indigenous to Queensland, New South Wales and Victoria. It reaches at least 15m and is often grown for its spotted, smooth barked trunk. It has a prolific display of white flowers from May to June. Hardy and adaptable, it is useful where shade and shelter are desired and it is also attractive to birds.

Lophostemon confertus has the common name of Brush Box. It is a small to medium tree reaching 10m in height with shiny, dark green leaves to 15cm long. Feathery white flowers appear mainly from December to February. It is a hardy tree, which rarely reaches its full size in cultivation. It is widely used as a street tree.

Jacksonia scoparia is a native of Queensland and New South Wales. It reaches a height of 3 metres. It is an upright shrub with narrow, greyish foliage. Profuse orange to yellow, fragrant pea-flowers appear from September to November, providing an eye-catching display. It prefers a warm well-drained position and is tolerant of frost.

Melaleuca leucadendron is a medium to large tree with papery bark and broad leaves. Cream flower spikes to 15cm long appear mainly from June to February with sporadic flowering at other times. This tough melaleuca will tolerate moist or even water-logged situations. It grows to 15 metres and is a good species for attracting birds.

Melaleuca viridiflora is a native of Queensland, Western Australia and Northern Territory. It is a large shrub to medium tree with leaves to 15cm long. Pale green or red flower spikes appear through most of the year. It is variable both in habit and flower colour and is best suited to tropical or sub-tropical areas. It grows to 8 metres.

If you are trying to establish a garden in an area of heavy soil, these are only a few of the natives that can be utilised to introduce beauty and colour – and birds!