Blue boronia

Appearance

"Cyanothamnus coerulescens" is an erect shrub that grows to a height of 0.2–0.6 m with branchlets that are warty glandular. The leaves are usually simple,, more or less cylindrical in shape to narrow oblong or elliptic, 5–10 mm long and 0.5–1.5 mm wide. The flowers are bright blue, lilac-coloured or white and are arranged singly in leaf axils or in dense, leafy spikes on the end of the branches. Each flower has a pedicel 2–5 mm long. The four sepals are triangular to broadly egg-shaped, 1.5–7 mm long with their bases overlapping. The four petals are more or less egg-shaped with a small, pointed tip, 3–9 mm long with their bases overlapping. The eight stamens and the style are slightly hairy. Flowering mostly occurs from August to November and the fruit are 3–4 mm long with the petals remaining on the end.

Naming

Blue boronia was first formally described in 1854 by Ferdinand von Mueller who gave it the name "Boronia coerulescens" in "Transactions of the Philosophical Society of Victoria". In a 2013 paper in the journal "Taxon", Marco Duretto and others changed the name to "Cyanothamnus bussellianus" on the basis of cladistic analysis. The specific epithet is a Latin word "caeruleus" meaning "sky blue" with the ending "-" signifying "beginning of" or "becoming".: 135 

In 2019, Paul Graham Wilson described three subspecies in the journal "Nuytsia". The names have subsequently been changed to reflect the change in the genus name:
⤷  "Cyanothamnus coerulescens" F.Muell. subsp. "coerulescens" has flowers in leaf axils;
⤷  "Cyanothamnus coerulescens" subsp. "spicatus" Duretto & Heslewood that has flowers in dense, leafy, spike-like racemes;
⤷  "Cyanothamnus coerulescens" subsp. "spinescens" Duretto & Heslewood, originally described in 1863 as "Boronia spinescens" by George Bentham, is a variable subspecies with spreading, often pungent branchlets and is similar to subspecies "coerulescens".

Distribution

Blue boronia grows in mallee woodland. Subspecies "coerulescens" occurs in the south-west of Western Australia, in South Australia, Victoria and in the far south-west of New South Wales. Subspecies "spicata" occurs in Western Australia between Wubin and Muntadgin and "spinescens" is found in similar areas to subspecies "coerulescens" but only in Western Australia.

Status

All three subspecies of "C. coerulescens" are classified as "not threatened" by the Western Australian Government Department of Parks and Wildlife.

Habitat

Blue boronia grows in mallee woodland. Subspecies "coerulescens" occurs in the south-west of Western Australia, in South Australia, Victoria and in the far south-west of New South Wales. Subspecies "spicata" occurs in Western Australia between Wubin and Muntadgin and "spinescens" is found in similar areas to subspecies "coerulescens" but only in Western Australia.