It has been recognised for many years that the group of plants commonly referred to as the 'Australian heaths' are closely related to plants in the cosmopolitan heath family, the Ericaceae, which had been regarded as being poorly represented in Australia, with only a handful of species occurring here. The Ericaceae is widely distributed in the northern Hemisphere and Africa and includes such well known garden plants as Erica, Rhododendron, Azalea and Pieris. Several Erica species (notably Erica lusitanica) have become naturalised in Australia, having escaped from garden cultivation.
Until recently the Australian heaths had been regarded as being sufficiently distinct from members of the Ericaceae to warrant being placed in a separate family, the Epacridaceae, which takes its name from the well known genus Epacris. However, recent research has indicated that members of the Epacridaceae are more closely related to the Ericaceae than previously thought. As a result, most botanical institutions now recognise that members of the Epacridaceae are more correctly placed within the Ericaceae as the subfamily Epacridoideae (previously subfamily Styphelioideae - see footnote). As a result, the name 'Epacridaceae' is now obsolete.
While most Australian members of the heath family belong to the subfamily Epacridoideae there are a few species in two other subfamilies. Australian members of the Ericaceae can be summarised as follows:
The family Ericaceae is widely distributed worldwide, particularly in the northern hemisphere. However, the subfamily Epacridoideae is distributed mainly in Australia with a few species being found in countries to the north of Australia as well as in New Zealand, the Pacific islands and South America (see map).
|Worldwide distribution of the Subfamily Epacridoideae
A distinguishing feature of the subfamily Epacridoideae compared to other members of the Ericaceae is the palmate venation of the leaves of most members of the former. "Palmate venation" refers to the way that several main veins radiate from the base of the leaf. Because of the small leaves in many species in the subfamily Epacridoideae, the veins often appear to be parallel.
A number of species of Australian Ericaceae are attractive plants for cultivation due to their prolific and colourful flowers. The genus Epacris is the most commonly cultivated member of the family and one member of the genus, Epacris impressa (common or pink heath) is the floral emblem of Victoria. Apart from Epacris, other members of the subfamily Epacridoideae are not often seen in general cultivation but genera grown by enthusiasts include Astroloma, Dracophyllum, Leucopogon, Prionotes, Richea, Sprengelia, Styphelia and Woollsia.
|Palmate venation on
Photo: Brian Walters
Members of the other Australian subfamilies are uncommon in cultivation apart from the spectacular Rhododendron lochiae and occasionally Paphia meiniana, an attractive semi-climbing species with waxy tubular flowers. Both of these species are native to rainforest in north Queensland.
Several Australian members of the family were introduced into cultivation in Europe within a few years of British exploration of the east coast of Australia in the late 1700s - early 1800s. Species grown in Europe included species of Astroloma, Brachyloma, Epacris, Leucopogon, Lissanthe, Melichrus, Monotoca, Styphelia and Woollsia.
For the most part, the Australian Ericaceae are small shrubs but a few species occur as small trees. They can be found in a range of habitats and are a common component of low, exposed vegetation known as heathland. Often they will be found in areas of constant moisture but also occur in temperate open forest and woodland, sub-alpine areas and the coastal zone. They tend to be absent in the arid zone and only a few are found in rainforests.
Footnote: Species in the subfamily Epacridoideae were initially placed within the subfamily Styphelioideae. However, a 2012 change in the botanical rules of nomenclature made this classification invalid and the subfamily name was changed to Epacridoideae. A short discussion on this change can be found in the article Typification of some names in Epacridoideae (Ericaceae) by Darren M. Crayn, Kathleen A. Kron and Benjamin C. M. Potter (Telopea, Volume 17: 319-321, November 2014).