Sydney Red Gum

''Angophora costata'', commonly known as Sydney red gum, rusty gum or smooth-barked apple, is a species of tree that is endemic to eastern Australia. Reaching in height, the species has distinctive smooth bark that is pinkish or orange-brown when new and fades to grey with age. Its lance-shaped leaves are arranged in opposite pairs along the stems, with white or creamy white flowers appearing from October to December. The flower buds are usually arranged in groups of three, followed by ribbed, oval or bell-shaped fruit.

Description

''Angophora costata'' is a tree that typically grows to a height of and forms a lignotuber. It has smooth pinkish or orange-brown bark that weathers to grey and is shed in small scales. Young plants and coppice regrowth have sessile, elliptical to egg-shaped leaves arranged in opposite pairs with a stem-clasping base, long and wide. Adult leaves are arranged in opposite pairs, glossy green but paler on the lower surface, lance-shaped or curved, long and wide on a petiole long. New leaf growth is strongly tinted with red. The flower buds are arranged on the ends of branchlets on a branched peduncle long, each branch of the peduncle with usually three buds on pedicels long. Mature buds are oval to globe-shaped, up to long and wide. There are five sepals up to long and the petals are white to creamy white with a green keel, long and wide. Flowering occurs from October to December. The fruit is a oval or bell-shaped capsule up to long and wide. New seedlings have petiolate round cotyledon leaves 1.5 cm wide and long.

Taxonomy and naming

Sydney red gum was first formally described in 1788 by German botanist Joseph Gaertner and given the name ''Metrosideros costata'' in his book ''De Fructibus et Seminibus Plantarum'', from material collected by surveyor David Burton around Port Jackson. The specific epithet (''costata'') is a Latin word meaning "ribbed". English botanist Richard Anthony Salisbury named it ''Metrisoderos apocynifolia'' in his 1796 work ''Prodromus stirpium in horto ad Chapel Allerton vigentium''. Spanish taxonomist Antonio José Cavanilles erected the new genus ''Angophora'' in 1797 in his book ''Icones et Descriptiones Plantarum'', giving the species the name ''Angophora lanceolata''. English botanist George Bentham used this last name in his '' Flora Australiensis'' in 1867.

English botanist James Britten changed the name to ''Angophora costata'' in the ''Journal of Botany, British and Foreign'' in 1916.

In 1986, Gregory John Leach described three subspecies in the journal '' Telopea'' and two names have been accepted by the Australian Plant Census:
* ''Angophora costata'' (Gaertn.) Britten subsp. ''costata'' has a glabrous floral cup and fruit mostly less than wide;
* ''Angophora costata'' subsp. ''euryphylla'' L.A.S.Johnson ex G.J.Leach has a hairy floral cup and fruit more than wide. It is found only in a small area including Putty, Howes Valley and Judge Dowling Range in central New South Wales. Genetic analysis published in 2021 showed it not to be distinct from subsp. ''costata''.

A third subspecies, subsp. ''leiocarpa'' was reclassified as a separate species ''Angophora leiocarpa''. A phylogenetic analysis of the genus published in 2021 confirmed its genetic distinctness from the two ''costata'' subspecies.

Recent genetic work has been published showing ''Angophora'' to be more closely related to ''Eucalyptus'' than ''Corymbia'', and the name ''Eucalyptus apocynifolia'' has been proposed for this species if it were to be placed in the genus ''Eucalyptus''. This has not been taken up by the botanical community.

Common names include Sydney red gum, rusty gum, smooth-barked apple, and smooth-barked angophora. Aboriginal people from the Sydney region knew the tree as ''kajimbourra''.

Distribution and habitat

''Angophora costata'' grows in sandy soil, often over sandstone and occurs naturally in Queensland and New South Wales. It is widely distributed in south-eastern Queensland and disjunctly in the White Mountains National Park. In New South Wales it mainly occurs in coastal areas south from Coffs Harbour to Narooma and as far west as the Blue Mountains.

It is found from sea level to an altitude of in areas of predominantly summer rainfall receiving a year. Maximum temperatures across its range vary from and minimum temperatures from , with anywhere from 0 to 50 days of frost.

In Victoria it is a commonly planted ornamental and is naturalised in some places.

It grows in open forest and woodland, in association with such species as Sydney peppermint (''Eucalyptus piperita''), bangalay ('' E. botryoides''), grey gum ('' E. punctata''), blue-leaved stringybark ('' E. agglomerata''), white mahogany ('' E. acmenoides''), broad-leaved white mahogany ('' E. umbra''), large-fruited red mahogany ('' E. scias''), red bloodwood ('' Corymbia gummifera''), yellow bloodwood ('' C. eximia''), pink bloodwood ('' C. intermedia'') lemon-scented gum ('' C. citriodora''), turpentine ('' Syncarpia glomulifera''), forest oak (''Allocasuarina torulosa''), and cypress pines (''Callitris'' species), and in hind dune communities with wedding bush (''Monotoca elliptica'') and burrawang (''Macrozamia communis'').

Ecology

''Angophora costata'' trees can live over 100 years. The species responds to bushfire by resprouting from epicormic buds and its lignotuber; shoots on branches of older specimens arise a month, while shoots resprout from the trunk and base
young plants within a month of a hot fire. Seedlings appear within 9 to 10 months.

The tree is parasitised by the long-flowered mistletoe (''Dendrophthoe vitellina'').

The flowers are eaten by the grey-headed flying fox (''Pteropus poliocephalus'') and little red flying fox (''P. scapulatus''), while the seed is eaten by the crimson rosella (''Platycercus elegans'').

Although the bark of ''A. costata'' is smooth, many invertebrates are found there. Several spiders in the family Salticidae, including '' Servaea vestita'', and pseudoscorpions live under loose bark. The flattened bug '' Stenocotis depressa'' evades detection by camouflage, and cockroaches and huntsman spiders live under the loose bark at the base of the trunk.

''Angophora costata'' is also susceptible to the fungal pathogens ''Quambalaria pitotheka'', '' Aulographina eucalypti'' and ''Cryptococcus neoformans''.

Uses

Use in horticulture

Smooth-barked apple grows well in a variety of situations and can be easily grown from seed in a loose, well-drained seed-raising mixture. Some specimens have straight trunk but others have a more branching habit with twisted trunks. The tree sometimes sheds branches and should not be planted close to buildings.

Timber

The heartwood is hard though not durable. Pale pink-brown in colour, it has a density of 755-1045 kg/m³ and a coarse texture. It is not suitable for use on the ground, though has been used for fencing and rough flooring. The pale sapwood has a width of up to 5 cm (2 in) and is susceptible to attack by borers of the genus ''Lyctus''.

Honey

This tree produces abundant pollen but little nectar. and the honey produced is not highly regarded.

Significant individuals

Angophora Reserve in the Sydney suburb of Avalon was named after a huge individual, reportedly around 300 years of age. That tree died in the late 20th century. Also in Sydney, the upper Lane Cove River Valley has several large Sydney red gums, one near Conscript Pass was measured at 45 metres tall. The largest known living tree in New Zealand (241 cm diameter) is located at Hobsonville near Auckland.

Gallery

File:Angophora costata - leaves (adult).jpg, Adult leaves
File:Angophora costata - inflorescence 01.jpg, Inflorescence
File:Starr 020203-0021 Angophora costata.jpg, Fruit with ridges
File:Angophora costata - trunk bark.jpg, Trunk bark
File:Angophora costata - shedding trunk bark.jpg, Shedding trunk bark
File:Angophora costata - upper trunk.jpg, Upper trunk
File:Angophora costata Habit.jpg, Twisting habit

References

{{Taxonbar, from=Q4564056

costata
Flora of New South Wales
Flora of Queensland
Trees of Australia
Ornamental trees
Plants described in 1788
Taxa named by Joseph Gaertner