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Cyanothamnus nanus var. hyssopifolius

Dwarf Boronia

Family: Rutaceae

A shrub to 0.3 metres high, erect or sprawling to prostrate.

It is found as far north as Mt Wilson west of Sydney, growing south-south-west from here mostly in the tablelands regions, including the southern highlands, through the ACT and into Victoria, from as far west as Albury, extending further east.

It is found in heathland as well as dry sclerophyll woodland and forest on the upper slopes and ranges, usually on sandstone and derived sandstone soils, often hanging over rocks.

The branchlets are hairy between leaves and have glandular-warty protrusions.

Cyanothamnus spp. produce opposite leaves which can be simple or compound (sometimes on the same plant) and are usually aromatic (sometimes strongly-so).
In this species, leaves appear simple (or uni-foliolate) linear to elliptic, to 25 mm long and 2 mm wide, with an acute apex.

Cyanothamnus have complete flowers (bisexual and with all whorls present). The flowers are produced either solitarily or in groups, in the leaf axils, or, at the branch terminals. There are usually four sepals, four petals and generally eight stamens, surrounding one female part (carpel). Flowers are often pink to purple, which makes them easily identifiable in NSW bushland.
In this species, flowers are white to pale-pink, produced solitarily in leaf axils, occurring October–January.

The fruit of Cyanothamnus are described as a schizocarp-capsule; a capsule that splits into even segments, which each segment called a coccus. The cocci are approximately 2 mm long.

In the garden

Not much is known regarding the cultivation of this species. It is not commonly cultivated. It may be more widely cultivated in the future. It grows in sandstone rocky areas and so may need similar soil-conditions to thrive.

Growing boronias (including Cyanothamnus) can be a frustrating experience and they have a reputation for being difficult. Their attractiveness has led to substantial efforts to cultivate them. One tip is to try to grow forms that are local to your area, rather than attempting to grow those species from interstate. There are certainly some species that have proven easier to grow than others.

Most Boronias have a short life span of two to three years in a garden situation but are a rewarding plant while healthy as they provide lovely fragrance and flowers in Spring.

For them to grow at their best, select a position with dappled sunlight and especially protection from hot afternoon sun in summer, as well as from wind, which they dislike.

The soil must be well drained and have an even supply of moisture. If they dry out, they will surely die.

Planting on a slight slope is said to work well.

For a longer life, the best way to grow them is in a medium sized pot, say 30 cm in diameter where drainage and moisture can be controlled. A sheltered patio or courtyard that receives at least a few hours sunlight a day would be ideal

Fertilise after flowering.

The conventional wisdom is, think deeply about which species to plant and the location to plant it.

Propagation

Boronias (including Cyanothamnus) can be propagated from cutting but, overall, you will have limited success with most but not all species.

Other information

This species, until 2020, went by the name of Boronia nana var. hyssopifolia
Some species of NSW Boronia have been moved to this genus and are published on this database as such.

There is only one variety recognised in NSW. Three varieties, including this one, are recognised in Victoria. This variety has simple leaves where the other varieties have tri-foliolate.

Most Cyanothamnus species would die in fire and regenerate from the seedbank.

Cyanothamnus – cyano from Ancient Greek. kuáneos meaning “dark blue” and -thamnus (Θάμνος) meaning “bush” or “shrub” – referring to many species in the genus having blue flowers.
nana – Latin meaning “dwarf” – referring to the small size of the species.
hyssopifolia – Latin – with leaves like Hyssop (Hyssopus) – a genus in the Lamiaceae family.

This species is not considered to be at risk of extinction in the wild.

Australian Native Plants Society Australia – Boronia Profile Page
http://anpsa.org.au/boronia9.html

Wikipedia – Cyanothamnus and Cyanothamnus nanus Profile Page
https://en.wikipedia.org/wiki/Cyanothamnus
https://en.wikipedia.org/wiki/Cyanothamnus_nanus

Gardening with Angus Website – Boronia for Beginners
https://www.gardeningwithangus.com.au/boronias-for-beginners-2/
https://apps.lucidcentral.org/plants_se_nsw/text/entities/boronia_nana_var._hyssopifolia.htm

NSW Flora Online (PlantNET) – Boronia nana var. hyssopifolia Profile Page
https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=in&name=Boronia~nana

By Jeff Howes, edited Dan Clarke