Scientific
classification
Kingdom: Plantae
(unranked): Angiosperms
(unranked): Eudicots
(unranked): Rosids
Order: Sapindales
Family: Rutaceae
Genus: Citrus
Species: C. australasica
Binomial
name ‘Citrus australasica F.Muell.
The
Australian finger lime plant (Citrus australasica) is a thorny understorey
shrub or small tree of lowland subtropical rainforest and dry rainforest in the
coastal border region of Queensland and New South Wales, Australia. It has
edible fruits which are under development as a potential new commercial crop.
According
to the Swingle system it is not part of the genus citrus, but in a related
genus Microcitrus.
The plant
is 2–7 metres in height. Leaves are small, 1–6 cm long and 3–25 mm wide, glabrous,
with a notched tip and crenate towards the apex. Flowers are white with petals
6–9 mm long. The fruit is cylindrical, 4–8 cm long, sometimes slightly curved,
coming in different colours, including pink and green.
Early
settlers consumed the fruit and retained the trees when clearing for
agriculture. Colonial botanists suggested that they should be cultivated.
The finger
lime has been recently popularised as a gourmet bushfood. The globular juice
vesicles have been likened to a "lime caviar", which can be used as a
garnish or added to various recipes. The fresh vesicles have the effect of a
burst of effervescent tangy flavour as they are chewed.
The fruit
juice is acidic and similar to that of a lime. Marmalade and pickles are also
made from finger lime. The finger lime peel can be dried and used as a
flavouring spice.
Commercial
use of finger lime fruit started in the mid-1990s in boutique marmalades made
from wild harvested fruit. By 2000 the finger lime was being sold in
restaurants, including the export of fresh fruit.
The finger
lime has been recently grown on a commercial basis in Australia in response to
high demand for the fruit. There is an increasing range of genetic selections
which are budded onto citrus rootstock. With the sudden high market demand for
the fruit the primary source of genetic material for propagation has been
selections from wild stock.
Research
conducted in the 1970s indicated that a wild selection of C. australasica was
highly resistant to Phytophthora citrophthora root disease, which has resulted
in a cross-breeding program with finger lime to develop disease-resistant
citrus rootstock.
The CSIRO
has also developed several Citrus hybrids by crossing the finger lime with
standard Citrus species. These hybrids have created many cultivars which
generate finger limes in many different colors ranging from light pink to deep
blue-green. Finger lime is thought to have the widest range of color variation
within any Citrus species.
