Coastal areas of Australia are often affected by an excess of salts in the soil. The same problem affects inland areas, especially on flat land where the water table lies close to the surface. Too much salt has a detrimental effect on plants. But planting salt-tolerant species can actually improve the situation. If enough such plants are added, there will be an eventual lowering of the water table, resulting in water flowing through the soil and dissolving and dispersing some of the salt.
There is a range of Australian natives which are suited to use in gardens with a moderate degree of salinity.
Acacia ligulata or Umbrella Bush grows to 5 metres and is hardy and decorative. Unless pruned, it will stay bushy to ground level. Globular bright yellow to orange flowers are produced from August to October with odd blooms also appearing throughout the year. It prefers full sun and is drought- and frost-resistant.
Carpobrotus modestus is also called Inland Pigface. It is a prostrate plant with thick, fleshy, juicy 3-sided leaves and daisy-like flowers. The flowers are light purple shading to white near the centre. Carpobrotus plants are well known for their ability to survive in hot, dry situations. They are useful as living mulches and for soil erosion control.
The Casuarina glauca or Swamp She-oak is a medium to tall tree. It has light brownish male flower spikes from July to October. It is hardy and suited to moist or well-drained positions. It may sucker to form a copse and is not affected by frost.
Melaleuca lanceolata or Moonah grows to 3 metres and has a dark, hard-barked trunk. White to cream brushes appear from October to February and flowering can be profuse. It is relatively slow-growing and prefers sunny well-drained sites. It will also tolerate exposed coastal conditions and alkaline soils.
Myoporum insulare or Boobialla is endemic to New South Wales. It is a bushy shrub with foliage to ground level. White starry flowers appear mainly from September to December. It is excellent as a screening plant or as a windbreak for exposed conditions.
The following species are all very attractive to birds and well worth a place in any garden, not just those battling saline conditions.
Callistemon salignus is also called the Willow Bottlebrush. It is commonly grown as a small tree and reaches around 8m high in cultivation. The new foliage is often bright pink to red with white to deep pink flower spikes from September to December. It is a hardy plant, suited to a wide range of conditions.
Eucalyptus botryoides or Southern Mahogany may grow as an upright forest tree or, in exposed conditions, it will branch and reach a height of around 12m. Cream flowers are produced in summer and autumn. It can be fast-growing and is very suitable for coastal conditions as it is able to withstand strong, saline winds. It is not a tree for small gardens.
Eucalyptus kondininensis or Kondinin Blackbutt is endemic to Western Australia and grows to 8 metres. In its natural state, it is always associated with salt and frequently found on the edges of salt lakes.It bears profuse, white to cream flowers mainly from November to December. The buds and fruits come straight off the branchlets and have no stalks. It occurs naturally near salt lakes in WA and is highly tolerant of saline conditions.
Another Western Australia native is Eucalyptus platypus var. heterophylla or Moort which grows to 4 metres and is usually single trunked in cultivation. It has a profuse display of cream to yellow-green flowers mainly from October to March. It is hardy, drought tolerant, responds well to pruning and is an excellent choice for screen or windbreak use. It is also an excellent choice for heavy, clay soils.
Also from WA, is the Eucalyptus stricklandii or Strickland Gum. This ornamental variety has a rough, black base to the trunk which gives way to smooth, grey to cinnamon-coloured bark on the upper trunk. The initial growth is upright then branches spread out to form a wide crown. It has an attractive display of bright yellow flowers from November to March. The flower buds and terminal branchlets have a powdery, white surface.
Establishing a garden under saline conditions is a challenge but planting the right species can make the task much easier.