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Zieria involucrata

Family: Rutaceae

A narrow and erect shrub, growing to a height to 2 metres, with an overall green-grey appearance.

It has a very restricted distribution, growing in the north and west of Sydney, in areas such as Marramarra National Park near Maroota, Canoelands; Parr State Conservation Area north of Colo and west of St Albans and further north; then around Kurrajong, Springwood/Faulconbridge and north of Wentworth Falls.
It is typically found in dry and wet sclerophyll woodland and forest, on Hawkesbury sandstone as well as Narrabeen Group sandstone soils, as well as Quaternary alluvium in some cases, usually in gullies.
It is a listed threatened species in the wild.

The branches are covered in hairs which give a velvet-texture.

Zieria spp. have leaves arranged in opposite pairs, compound with three leaflets (tri-foliolate) or one leaflet (uni-foliolate). When tri-foliolate, 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, the leaves can be a mixture of tri-foliolate and uni-foliolate leaves, in varying ratios (sometimes most leaves uni-foliolate), densely covered with hairs which form a soft, velvety covering (tomentum); to 55 mm long and to 15 mm wide; upper surface mid to dark-green, lower surface grey-green.

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 flower clusters consist of up to 25 flowers, with clusters shorter than the leaves, white with pink tinges, and slightly hairy, occurring from August to October. The flower clusters are surrounded by small bracts.

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 are hairy, lacking an oil body (elaisome).

 

In the garden

This species does not have history of cultivation and not much is currently known about its cultivation potential. It may be more readily cultivated in the future. A note is given here that other threatened Zieria spp. do well in cultivation.

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.

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. (This editor has observed this species regenerating from seed, after fire, in the field). There is some evidence that this species may also sucker from root zones.

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.

involucrataLatininvolucrum meaning a “wrapper”, “case” or “envelope”, or a “whorl” – usually referring to a whorl or ring of bracts surrounding flowers, which this species possesses.

This species is listed as threatened with extinction at the State and Commonwealth level with the categories of Endangered and Vulnerable respectively.

NSW Flora Online (PlantNET) – Zieria involucrata profile page

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

NSW Office of Environment and Heritage – Zieria involucrata profile page

https://www.environment.nsw.gov.au/threatenedSpeciesApp/profile.aspx?id=10858

Wikipedia – Zieria and Zieria involucrata profile page

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

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

By Jeff Howes, edited Dan Clarke