A robust large shrub, growing to potentially 10 metres tall.
It occurs from just into the south-east of Queensland, growing south in disjunct patches on the coast and tablelands of New South Wales with populations at areas such as north-east of Glen Innes, Laurieton, Olney and Watagans State Forest (west of the central coast), Mt Wilson, between Robertson and Kiama, Jervis Bay and then in small disjunct patches down to the south coast and inland of NSW, into south-eastern and southern-central Victoria, and into Tasmania where it is very common.
It grows in wet forest and at the margins of rainforest, usually on enriched soils.
Branches have prominent ridges where older leaves have fallen and are usually hairy when young.
Zieria spp. have leaves arranged in opposite pairs, compound with three leaflets (tri-foliolate) or one leaflet (uni-foliolate). When trifoliolate, the leaflets are often similar in shape with the middle leaflet often larger, and with leaves usually strongly odorous, green to grey-green.
In this species leaves are trifoliolate, with leaflets varying in size and shape but mostly lanceolate to oblong, to 90 mm long and to 15 mm wide with a stalk to 30 mm long. Both surfaces of the leaf are dotted with oil glands with a strong odour that many find unpleasant.
Zieria spp. have flowers arranged in groups (cymose clusters) in the leaf axils and have four sepals joined at the base and four petals, alternating with the sepals. There are four stamens and four fused carpels.
In this species flowers are white or pale pink and are arranged in large clusters in upper leaf axils, the clusters usually shorter than the leaves, petals are to 7 mm long, with flowering occurring from September to November.
Zieria have a fruit described as a schizocarp-capsule which splits into segments called cocci (singular coccus).
Fruit generally have four cocci, each containing one or two seeds.
In this species, the capsule contains four cocci, each of which have an ant-attracting elaiosome — a structure on the surface of a seed that secretes and stores oil.
Not much is known about this species in cultivation. It may be more readily cultivated in the future.
Many Zieria make interesting garden plants and deserve a place in gardens. They are a member of the Rutaceae family which include the genera Boronia, Philotheca and Crowea, all of which can be challenging to grow.
Some species are more commonly grown. They require good drainage, preferably on a light sandy soil and a semi-shaded area. They have soft foliage, can be pruned into nice-rounded shrubs and can flower prolifically.
Check local native nurseries for any species being propagated.
In common with most members of the Rutaceae, propagation from seed is difficult but cuttings usually strike readily from current season’s growth.
Three subspecies are currently recognised in NSW
• Zieria arborescens subsp. arborescens; – taller robust plant with less distinct branch ridging;
• Zieria arborescens subsp. decurrens – smaller plant to 3 metres tall with more distinct branch ridging – occurring only in the Jervis Bay area.
• Zieria arborescens subsp. glabrifolia – large plant, only growing in the Torrington and Tenterfield in NSW, in dry sclerophyll forest.
Zieria is a genus strongly odoriferous soft-woody shrubs, or small trees, with over 40 species described, all of which are endemic to Australia except for one species which is found in New Caledonia. They occur in all Australian states except Western Australia but the genus is under review and a number of species are yet to be described or the description published.
Zieria are similar to the better known genus Boronia but can be distinguished by the number of stamens in the flowers – four and eight in Boronia.
This species is toxic to cattle.
Most Zieria would die in a bushfire and regenerate from seeds. Suckering from roots may be possible.
Zieria – named in honour of Jan Zier (d. 1793), by Sir James E. Smith. Zier was a Polish botanist and cryptogam (ferns, mosses, lichen and fungi) specialist, for which there is little information online. He assisted Jacob Friedrich Ehrhart, the Director of the Botanical Garden of Hannover.
arborescens – Latin – meaning “tree-like” or “almost a tree”.
Not considered to be at risk in the wild.
Plants of South Eastern NSW – Zieria arborescens profile page
Wikipedia – Zieria and Zieria arborescens profile page https://en.wikipedia.org/wiki/Zieria
NSW Flora Online – Zieria arborescens profile page
Australian Weeds and Livestock – Mangrove Mountain Computer Club – Zieria arborescens profile page