By: Penny Woodward | September 14, 2015
With the weather starting to warm and moisture still in the soil, now is the perfect time to plant citrus, and why not think about planting an Australian native citrus? Australia is fortunate to have several species of native citrus which, although known to Indigenous Australians and to the first white settlers and explorers, have only been commercially exploited in the last few decades.
Australian finger lime, Citrus australasica (previously Microcitrus australasica), grows as a shrub to small tree with slender thorn-covered stems, small oval leaves and numerous finger-shaped fruit about the size of a man’s thumb. It grows naturally in sub-tropical rainforest in New South Wales and Queensland as an under-story tree, but can be cultivated in frost-free regions all over Australia. Bushes can take anywhere from 5 to 17 years to bear fruit and may not fruit every year, although grafted forms will fruit sooner and more often. There is enormous variation in the size, acidity and colour of the fruit. Naturally occurring plants have been found with green, yellow, black, purple, blood red and even crimson fruit. The pulp is usually green.
Round lime, Citrus australis (previously Microcitrus australis) grows as a vigorous tree that can be as tall as 15 metres. It comes from south-eastern Queensland where it is found in sub-tropical rainforest. The rounded fruit can reach 8 cm in diameter and are eaten when green or when they turn yellow. Less common, but closely related Australian limes found in similar habitats are Mt White lime (C. garrawayae), Kakadu lime (C. gracilis), Russell River lime (C. inodora) and Maiden’s Australian wild lime (C. maideniana).
The Desert lime, Citrus glauca (previously Eremocitrus glauca) comes from semi-arid regions of Queensland, New South Wales and South Australia. It is extremely drought tolerant, can withstand extreme heat and cold and will grow in a range of soils. Its growth habit is variable, ranging from multi-stemmed shrubs to slender trees of 10 metres. The pale yellow green fruit of about 2 cm in diameter is round and seedless.
There are now many cultivated hybrids that have been developed through natural selection from existing trees or crosses between introduced and native citrus. Two of the latter are the ‘Australian Blood' lime and ‘Australian Sunrise' lime. Others have names like Rainforest Pearl, Ruby, Alstonville, Blunobia Pink Crystal, Pink Ice, Limeburst and many more. Skin colours vary from green, yellow, purple and pink to bright red, and mature fruit can be anything from a few centimetres to 12 cm long. Mostly fruit pulp is unique with a ‘caviar like’ appearance that also comes in many different colours, not necessarily the same as the skin. The delicious tiny balls of intensely flavoured tangy fruit are superb in a huge range of sweet and savoury dishes. The intensity of skin and pulp colour, as well as flavour, can vary as a result of flowering times and climate. Fruit seediness can also vary with some cultivars being almost seedless and others having many seeds.
Limes are relatively disease free. Scale infestation can be tackled with soapy water and a toothbrush, black aphid that cause curling and withering of young growth can be controlled by soap spray or pest oil and larger sap sucking bugs can be removed and squashed. Many of these limes are available to home gardeners, others are only grown for commercial production. Ask at you local nursery and if they don't have them they should be able to order them in. There is an interesting NSW Prime Fact sheet from the Department of Primary Industries with more information here.