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Zieria granulata

Hill Zieria, Illawarra Zieria

Family: Rutaceae

A shrub growing to 3 metres typically, (potentially reaching 6 metres). It is strongly aromatic.

It has a highly restricted natural occurrence, growing only in the Illawarra region of NSW, where it occupies several sites; from just north of Dapto to around Broughton Vale and Toolijooa. It is a listed threatened species.

It grows in dry sclerophyll forest and rainforest margins on rocky soils.

Branches are densely covered with warty protuberances with young branchlets covered in hairs.

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, leaves are tri-foliolate, with linear leaflets, up to 40 mm long and only about 1 mm wide, with toothed edges and with warty protuberances on both surfaces; upper surface dark to dull green and lower surface white due to stellate hairs, strongly aromatic.

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, the flowers are white and are arranged in many-flowered clusters of in leaf axils, each flower to 7 mm in diameter, occurring during spring and summer.

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 cocci contain reddish seeds about 2 mm long that have an oil body attached (elaisome) for attracting ants.

In the garden

This species has been grown in cultivation for at least 20 years now 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. It is grown successfully by APS members in Sutherland group, at least. Check local native nurseries for availability.

Light pruning after flowering will help to maintain the plant as a bushy, compact shrub. It can flower very heavily. Give it some space to spread out and be admired. This is a great example of where a threatened species can be sourced and planted in a garden.

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.

Propagation

In common with most members of the Rutaceae, propagation from seed is difficult but cuttings usually strike readily from current season’s growth.
Mass germination of seeds of this species has been observed following soil disturbance.

Other information

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.

Most Zieria would die in a bushfire and regenerate from seeds. Suckering from roots may be possible.

Zierianamed 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.

granulataLatin granulum, meaning “grains” or “granules / small particles” and the suffix –atus “possessive of”, referring to either the oil glands in the leaves or the warty protuberances on the stems which resemble grains.

This species is listed as threatened with extinction at both the State and Commonwealth level – with the category of Endangered.

NSW Flora Online (PlantNET) – Zieria granulata profile page

https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Zieria~granulata

Wikipedia – Zieria and Zieria granulata profile page

https://en.wikipedia.org/wiki/Zieria

https://en.wikipedia.org/wiki/Zieria_granulata

Australian Native Plants Society Australia – Item piece on Zieria granulata

http://anpsa.org.au/APOL33/mar04-9.html

NSW Office of Environment and Heritage – Zieria granulata profile page

https://www.environment.nsw.gov.au/threatenedSpeciesApp/profile.aspx?id=10856

Growing Illawarra Natives profile page:

https://finder.growingillawarranatives.org/plants/plant/526

 

By Jeff Howes, edited Dan Clarke