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On the Brink - 9
A series on Australian Plants at risk in their natural habitat.
Zieria granulata
Zieria is a genus of plants in the Rutaceae. It's closest relative is the much better known Boronia from which it differs in having 4 rather than 8 stamens. Generally, zierias are not popular in cultivation because they generally have smaller and less colourful flowers than Boronia.
Zieria granulata occurs in the Illawarra region of New South Wales where it is known from about 70 locations over a range of about 20 km in the Shellharbour/Kiama area. One or two populations occur within Budderoo National Park to the west of Jamberoo. A population further north at Kanahooka (near Lake Illawarra) is believed to have become established there through fill material brought in from the southern habitat. The species is commonly known as the Illawarra zieria.
The principal threat to the long term survival of the species is loss of habitat resulting from quarrying, residential development and road construction.
The species is listed as endangered under the Australian Government's Environment Protection and Biodiversity Conservation Act 1999. This listing means that the species faces "a very high risk of extinction in the wild in the near future, as determined in accordance with the prescribed criteria". Under the ROTAP* coding system it is classified as "2EC".
Zieria granulata is a small to medium shrub reaching 1.5 - 3 metres. Leaves are 3-lobed with long linear leaflets to about 40 mm long with margins that are revolute (curved under). The leaves have conspicuous oil glands that give the leaves a 'warty' appearance and they have a very strong aroma when crushed. The small flowers (about 4 - 5 mm diameter) occur in clusters from the leaf axils and are white with four petals. They occur in late winter and spring.
This species has been grown in cultivation for a number of years and it has proven to be very hardy in well drained soils in full sun or (preferably) semi shade. It withstands extended dry periods without supplementary watering and is tolerant of at least moderate frost.
* ROTAP: Rare or Threatened Australian Plants (1988). J.D.Briggs and J.H.Leigh, CSIRO Division of Plant Industry (Australian National Parks and Wildlife Service, Special Publication No.14).
Further information is available from a fact sheet published by the NSW National Parks an Wildlife Service.
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Australian Plants online - March 2004
Association of Societies for Growing Australian Plants
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