''Triunia'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of medium to tall shrubs or small trees found as understorey plants in rainforests of eastern Australia. Members of the plant family

Proteaceae The Proteaceae form a family (biology), family of flowering plants predominantly distributed in the Southern Hemisphere. The family comprises 83 genus, genera with about 1,660 known species. Australia and South Africa have the greatest concentr ...

, they are notable for their poisonous fleshy fruits or drupes. Only one species, ''T. youngiana'', is commonly seen in cultivation.

Taxonomy

Lawrie Johnson and

Barbara G. Briggs Barbara Gillian Briggs (born 1934) is one of the foremost Australian botanists. The '' IK'' lists 205 names of plants which have been published or co-published by her. She was one of the botanists in the Angiosperm Phylogeny Group, of th1998 APG ...

described the genus ''Triunia'' in their 1975 monograph " On the Proteaceae: the evolution and classification of a southern family". The group of species in this genus was previously recognised as a subgenus, ''Macadamiopsis'', of '' Helicia'' by Hermann Sleumer in 1955. ''T. youngiana'' was made the

type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...

. This plant had originally been described in 1864 as ''Helicia youngiana'' before being transferred to the genus ''

Macadamia ''Macadamia'' is a genus of four species of trees in the flowering plant family Proteaceae. They are indigenous to Australia—specifically, northeastern New South Wales and central and southeastern Queensland. Two species of the genus are comm ...

''. They initially placed the genus in its own subtribe, Triuniinae, within the tribe Helicieae. More recently, the genus has been placed in the tribe Roupaleae, Its closest relative is '' Eucarpha'',Sauquet, H., P. H. Weston, C. J. Anderson, N. P. Barker, D. J. Cantrill, A. R. Mast, and Savolainen, V. (2009). Contrasted Patterns of Hyperdiversifaction in Mediterranean Hotspots. Proceedings of the National Academy of Sciences of the USA 106 (1): 221–25. from

New Caledonia New Caledonia ( ; ) is a group of islands in the southwest Pacific Ocean, southwest of Vanuatu and east of Australia. Located from Metropolitan France, it forms a Overseas France#Sui generis collectivity, ''sui generis'' collectivity of t ...

Species

*'' Triunia erythrocarpa'' – Wet Tropics of north-eastern Qld endemic *'' Triunia montana'' – Wet Tropics mountains of north-eastern Qld endemic *'' Triunia robusta'' – south-east Qld restricted endemic *'' Triunia youngiana'' – north-east NSW to south-east Qld endemic (

)

Description

The members of the genus grow as shrubs to small trees, with simple green obovate to elliptical leaves and new growth covered in reddish hairs. The flowers are fragrant and arranged in terminal

raceme A raceme () or racemoid is an unbranched, indeterminate growth, indeterminate type of inflorescence bearing flowers having short floral stalks along the shoots that bear the flowers. The oldest flowers grow close to the base and new flowers are ...

s. Flowers are followed by small round red fruit, which are highly toxic. The seeds are round.

Habitat and ecology

The four species grow naturally only in eastern Australia between Dorrigo in mid-northern New South Wales and the Wet Tropics rainforests region of north-eastern

Queensland Queensland ( , commonly abbreviated as Qld) is a States and territories of Australia, state in northeastern Australia, and is the second-largest and third-most populous state in Australia. It is bordered by the Northern Territory, South Austr ...

. They grow in uplands and mountains rainforests, where they form part of the

understorey In forestry and ecology, understory (American English), or understorey (Commonwealth English), also known as underbrush or undergrowth, includes plant life growing beneath the forest canopy without penetrating it to any great extent, but above ...

. Two species grow naturally in south-eastern Queensland and one of them grows further southwards through to north-eastern New South Wales. Two other species are only known to grow about to the north in the uplands and mountains rainforests of the Wet Tropics region of north-eastern Queensland.

Cultivation

In cultivation, all four species grow into garden shrubs with attractive foliage, flowers and fruit, and can tolerate heavy shade to full sun. They require fair to good soil drainage and can be propagated by seed or cutting.

References

{{Taxonbar, from=Q7844607 Proteaceae genera Proteales of Australia Taxa named by Barbara G. Briggs Taxa named by Lawrence Alexander Sidney Johnson Taxa described in 1975