Rhododendron viriosum is a shrub to about 3 metres tall by about 1 to 2 metres wide.
It is found in tropical North Queensland, known from a few locations as far south as Herberton and Babinda-area (south of Cairns) – extending northwards to Gordonvale; then found west of Mossman and Port Douglas and then further north west of Cape Tribulation and south of Cooktown. R. lochiae is found on three peaks Bell Peak, Mt Bartlefrere and Mt Bellenden.
It is typically found in tropical rainforest including cloud forests and open rocky areas which adjoin such habitat, esepcially at high altitudes.
It tends to be semi-epiphytic – growing on rock shelves where it places its roots into cracks, as well as an epiphyte on other trees (similar to some fig-species).
A note is made here to account for an unusual taxonomic ‘dog’s breakfast’. Point form may be easier:
However, the “get-out-jail-card” here is that the Australian Plant Census has decided to recognise R. lochiae as the only species currently in Australia. So…we think this means we can still use the name for garden plants.
It is worth noting, however, that recent investigations have indicated that two distinct species do indeed exist i.e., Rhododendron lochiae (as per the type specimen) and Rhododendron viriosum (which is commonly cultivated). Do note that both species are described in the Australian Tropical Plants Online Key (see references below).
R. viriosum is found north of the Barron River in several geographic locations as far North as Mt Finnigan and as far west as the Windsor Tablelands.
The species are differentiated by R. lochiae having a distinct curved tubular corolla and R. viriosum the shorter and straight tubular corolla.
Rhododendron species tend to have simple and whorled leaves. In this species, they are in whorls or false-whorls, of 3 to 5, to 11 cm long and 7 cm wide, usually elliptic to ovate; cracking if they are bent, mid-green in colour with the underside marker by dark scales.
Rhododendron have 5-merous flowers. In this species, flowers are tubular with 5-lobes (trumpet-like), up to 5 cm long by 2.5 cm wide at the tips produced in umbels of up to 7 which tend to hand penduously; deep red-pink in colour; with 10 stamens on the inside of the tube; produced mostly from spring through to autumn.
The fruit is a capsule to 3 cm long and narrow.
To grow Rhododendron lochiae successfully, you will need a raised bed with moist, acid soil with a high organic content to mimic their natural high-mountain habitat in north Queensland rainforest conditions.
I planted mine about 25 years ago in my garden (in the northern Sydney suburb of Westleigh) and they are now approximately one metre high and about the same wide — yes they are slow growing.
They receive only dappled morning sun and shade for the rest of the day. My plants are happier with some supplementary watering as they flower better and after good soaking rains I am rewarded with a mass display of flowers from late spring through to autumn. The flowers are about 50 mm long by 30 mm across and occur in terminal clusters of up to six flowers, although the best my plants can do is four flowers. Perhaps my growing conditions are not ideal.
Plants can often be sourced at native nurseries.
Propagation is likely done from cuttings.
Existence of two species has been confirmed by research carried out jointly by the Australian Tropical Herbarium, James Cook University with assistance from the Australian Rhododendron Society and DNA analysis done by Massey University in New Zealand. All the botanical work was carried out by Prof Darren Crayn and his staff at Aust Tropical Herbarium James Cook University apart from the DNA work.
Thanks to Rob Hatcher for clarification on the two species. Rob is Collections Review Project Officer, Botanic Gardens and State Herbarium, South Australia, who was on several of the collecting trips with staff from Australian Tropical Herbarium, James Cook University as a member of Australian Rhododendron Society (and staff at Botanic Gardens Shoalhaven Heads).
Rhododendron – is from the Greek rodon (ῥόδον) meaning “rose” and dendron (δέντρο) meaning “tree”, in reference to the terminal flower clusters making this plant look like a rose-tree.
lochiae – named by Ferdinand Mueller after Lady Loch who was the wife of Sir Henry Brougham Loch (1827-1900), who was Governor of Victoria from 1884-89.
This species is not considered to be at risk of extinction in the wild. However, it has a niche habitat.
Australian Tropical Rainforest Plants – Rhododendron viriosum profile page https://apps.lucidcentral.org/rainforest/text/entities/rhododendron_viriosum.htm
Wrigley, J.W. & Fagg, M.I. (2001). Australian Native Plants – Propagation, cultivation and use in landscaping. 4th edition. New Holland Publishers, Pty. Ltd. Australia.
Australian Native Plants Society Australia (ANPSA) – Rhododendron lochiae profile page https://anpsa.org.au/plant_profiles/rhododendron-lochiae/