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Sandra Hardy
Industry Leader – Citrus, Industry & Investment NSW, Gosford
Primary Industries Institute
PrImefaCt 979JaNuary 2010
Phillip Wilk
District Horticulturist, I & I NSW, NSW Centre for tropical
Horticulture, Alstonville
Judy Viola
Proprietor and finger lime grower, Viola Citrus Nursery
Sheryl Rennie
Manager, Wild fingerlime
Australia has six species of native citrus, with the most well known and
cultivated species being the finger lime. The Australian finger lime
(Citrus australasica) is native to the rainforests of the border ranges of
SE Queensland and Northern NSW. In its natural habitat the finger lime
grows as an understorey shrub or tree up to 6 metres in height on a range
of soil types.
Trees are thorny, producing distinctive
finger shaped fruit up to 12 cm long with a typically green-yellow skin and
pulp. There is also a naturally occurring pink-red fleshed form of finger
lime known as Citrus australasica var. sanguinea. In the wild, finger limes
are genetically very diverse, with trees and fruit varying in size, shape,
colour and seediness. The pulp of the fruit is unique with separate juice
vesicles that resemble caviar. The individual juice vesicles (sometimes
referred to as crystals) are compressed inside the fruit and burst out when
the fruit is opened. Demand for finger limes has grown steadily over
the past decade, mainly as a result of its bush food status, unique
caviar-like pulp and attractive colour range, with most interest coming
from the restaurant trade. Fresh fruit are mainly used as a garnish for
seafood and the pulp is used for processing into sauces, jams and jellies.
Industry & Investment NSW has not yet undertaken any research trials on
growing finger limes. Most of the information in this Primefact has been
obtained from commercial growers on the north coast of NSW. Climatic
requirements
At present most commercial plantings of finger
limes are confined to northern NSW and southern Queensland, with a few
plantings dotted along the coast as far south as Sydney. Trees can probably
tolerate a wide range of climatic conditions including light frosts, but
ideally sites should be frost free and trees protected from prevailing hot
or cold winds.
Commercial finger lime orchards do well planted
in full sun. Some earlier plantings, however, incorporated protection from
full sun by inter-planting with taller native trees or covering trees with
shade cloth, to mimic the natural habitat of the plant. Varieties and
rootstocks Over the past twenty years growers and nurserymen have selected
a range of finger lime plants with different characteristics directly from
the bush or from seedling populations. These selections have then been used
as the ‘mother plants’ for vegetatively propagating identical
new plants.
All commercial citrus trees in australia are propagated vegetatively using
budwood, which ensures the new trees are identical to the original mother
plant. Citrus trees grown from seed are not used because they are not
always true to type, are slower growing and can take many years to bear
fruit. All commercial citrus trees are grown on specially selected citrus
rootstocks that have different characteristics including tolerance to a
range of soil, disease, pest and climatic conditions.
The
commercially available finger lime cultivars come in a variety of tree
shapes and sizes, from tall upright trees with open canopies and narrow
leaves to dense weeping shrubs with broader leaves. The mature fruit range
in size from 6 to 12 cm in length and come in a wide range of colours
including green, yellow, purple and pink to bright red. The pulp of the
fruit is unique with a ‘caviar like’ appearance that also comes
in a wide range of colours. The intensity of skin and pulp colour can have
some variation as a result of flowering times and climatic conditions.
Fruit seediness can also vary with some cultivars being almost seedless and
others having many seeds.
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