Alloxylon pinnatum

Alloxylon pinnatum
Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Eudicots
Order:	Proteales
Family:	Proteaceae
Genus:	Alloxylon
Species:	A. pinnatum
Binomial name
Alloxylon pinnatum (Maiden & Betche) P.H.Weston & Crisp
Range of A. pinnatum in northern New South Wales and southeastern Queensland
Synonyms
Oreocallis pinnata (Maiden & Betche) Sleumer Embothrium wickhamii var. pinnatum Maiden & Betche Embothrium pinnatum (Maiden & Betche) C.T.White

Alloxylon pinnatum, commonly known as Dorrigo waratah, is a tree of the family Proteaceae found in warm-temperate rainforest of south-east Queensland and northern New South Wales in eastern Australia. It has shiny green pinnate leaves, and prominent pinkish-red inflorescences which appear in spring and summer, followed by rectangular woody seed pods. It was previously known as Oreocallis pinnata for many years, until it was transferred to the new genus Alloxylon by Peter Weston and Mike Crisp in 1991. This genus contains the four species previously classified in Oreocallis that are found in Australasia.

Alloxylon pinnatum is a rainforest tree. Its terminal tubular flowers indicate that the species is pollinated by birds. Alloxylon pinnatum has proven difficult to cultivate.

Description

The Dorrigo waratah is a rainforest tree which reaches 25 m (80 ft) high and a non-buttressed trunk of 1.5 m (5 ft) diameter at breast height. The bark is greyish brown and covered in many small pimples, rendering it sandpaper-like in texture.^[1] The shiny light green leaves are alternately arranged along the stem, and up to 30 cm (12 in) long. Compound, they are pinnate with 2–11 leaflets.^[2] Among the green foliage there are occasional yellow leaves. New branchlets and leaves are covered in brown hair.^[1] There The pinkish-red compound flowerheads, known as inflorescences, are up to 20 cm (8 cm) across in spring to summer, and contain between 50 and 140 smaller flowers.^[2] The pollen is crimson.^[3] After flowering, the 8–10 cm (3.2–4 in) long woody seedpod develops. Cylindrical in shape, it splits down one side to release the seed, which are ripe from February to June. The seeds are arranged in two rows.^[1]

Alloxylon pinnatum can be distinguished from other members of the genus Alloxylon by its pinnate adult leaves unlike others which have simple adult leaves. Other species have inflorescences with fewer flowers (50 maximum), and have yellow pollen.^[3]

Taxonomy

First described as a variety of what was then known as Embothrium wickhamii by Joseph Maiden and Ernst Betche in 1911 after a collection by J.L.Boorman,^[4] the Dorrigo waratah was raised to species status and reclassified as Oreocallis pinnata by Dutch botanist Hermann Otto Sleumer in 1954.^[5] With the recognition of the distinctness of the Australian members of the genus Oreocallis and their reallocation to the new genus Alloxylon, it was given its current binomial name of Alloxylon pinnatum in 1991 by Peter Weston and Mike Crisp of the Royal Botanic Gardens in Sydney.^[6] The species name refers to the pinnate leaves. Aside from Dorrigo waratah, it has also been called the Dorrigo oak, red silky oak, tree waratah, pink silky oak, red oak, Queensland waratah, and waratah oak.^[7]

Alloxylon pinnatum and the other three tree waratah species lie in the subtribe Embothriinae, along with the true waratahs (Telopea), and Oreocallis and Chilean firetree (Embothrium coccineum) from South America.^[8][9] Almost all these species have red terminal flowers, and hence the subtribe's origin and floral appearance most likely predates the splitting of Gondwana into Australia, Antarctica, and South America over 60 million years ago.^[10] The position, colour and tubular shape of the flowers suggest they are bird-pollinated,^[2] and have been so since the Eocene radiation of nectar-feeding birds such as honeyeaters.^[11] Triporopollenites ambiguus is an ancient member of the proteaceae known only from pollen deposits, originally described from Eocene deposits in Victoria. The fossil pollen closely resembles that of Telopea truncata,^[12] A. pinnatum and Oreocallis grandiflora.^[13]

Cladistic analysis of morphological features within the Embothriinae showed A. pinnatum to be the earliest offshoot within the genus and sister to the other three species. Along with members of other genera in the Embothriinae, A. pinnatum as crimson pollen, while the other three Alloxylon species have yellow pollen.^[14]

Distribution and habitat

cultivated at Maleny, Queensland

The Dorrigo waratah is found in warm-temperate rainforest from altitudes of 700 to 1250 m (2200–4000 ft) along the McPherson Range in south-east Queensland and the Dorrigo Plateau in northern New South Wales, with dominant tree species such as coachwood (Ceratopetalum apetalum) and Antarctic beech (Nothofagus moorei).^[2] In Queensland it is associated with golden sassafras (Doryphora sassafras) and native crabapple (Schizomeria ovata). It commonly grows on southern aspects of hills and slopes.^[15]

It is classified as 3RCa under the Rare or Threatened Australian Plant (ROTAP) criteria for threatened species.^[16] and listed as near threatened under the Queensland Nature Conservation Act 1992.^[17]

Cultivation

Its bright, prominently displayed flowers and bird-attracting properties make it a desirable garden plant. It reaches only about 6–10 m (20–35 ft) in cultivation,^[7][18] but has proven difficult to grow.^[15] Alloxylon pinnatum has been successfully cultivated at the Australian National Botanic Gardens in Canberra in sheltered position in part-shade with a thick layer of mulch. It is propagated most easily by seed, which is ripe from February to June and keeps for twelve months or so.^[7] Seedlings often perish once 15 cm (6 in) high, and are difficult to transplant.^[1] It has also been grown at Mount Tomah Botanic Garden, where it was noted to demand very good drainage as well as shelter, and be somewhat exacting in its requirements. It is slow growing;^[18] specimens planted in 1989 have been flowering since 1999.^[19] The considerably easier to grow A. flammeum has been considered as a stock plant for grafting.^[20]

The pinkish red timber has been used for cabinet- and furniture making. It is soft and light, weighing 500 kg per cubic metre.^[1]

References