The Botanic Gardens is seen as the leading organisation in Eucalyptus research, with The Australian Botanic Garden as the location where many varieties of Eucalyptus species are displayed.
Eucalyptus Arboretums have been established/arranged in taxonomic groupings and can be viewed along Cunningham Drive and Caley Drive, which are the two main roads that circle the site. 9 out of the 14 arboretums, which are included in the genera Eucalyptus are displays along Cunningham drive, which is where the majority of Western Australian Mallee’s can be found. The remaining 5 arboretums can be viewed along Caley drive (southern route), which also where you would find the native theme garden collection.
Each of these Arboretums are listed below with a brief summary of their significance and how they are divided into the subgroups:
Adnataria: Boxes and Iron Barks
On the other side is another group of eucalypts which includes the Boxes and Iron Barks. Many of these are from northern Australia although you will also see the local Narrow-leaved Ironbark Eucalyptus crebra both here and throughout much of Mount Annan Botanic Garden. Mugga Ironbark Eucalyptus sideroxylon is widely grown for its contrasting black trunk and light grey leaves, and also for its hard timber. Yellow Box Eucalyptus melliodora is one of the most important trees for the production of honey.
Section Adnataria is a large and widespread group, occurring through all of Australia except Tasmania and the far southwest of Western Australia. The group is probably monophyletic, defined by the adnate anthers and petiolate early seedling leaves. Maximum diversity is reached in eastern Australia, with the greatest of infrasectional variety. A total of about 125 species in about 14 series can be recognised; only series Oliganthae being discussed here. The nature and definition of several of the possible series requires further study, and no key to the series is presented.
Aenigmataria: Sugar Gums
About 50m further on the left at the top of the hill there is a group of Sugar Gums (Eucalyptus cladocalyx). These trees have durable timber and are also widely planted as ornamentals. On the left-hand side about 50 m further is a group of Mallee’s — small multi-stemmed trees — mainly from Western Australia.
Angophora: Apple Gums A. bakerii, A. costata, A. floribunda, A. subvelutina (surviving species on site)
The first group of plants on the left are angophoras. These trees are commonly known as ‘Apples’ — perhaps because the gnarled branches, the foliage or the blossoms of some Sydney species reminded the early settlers of apple trees. Angophoras are related to eucalypts, but their flower buds lack covers and their leaves are arranged opposite each other rather than alternately. All the thirteen species of Angophora are from eastern Australia.
Araucaria: Sundial Hill and Mt Annan summit
About 100 m further along park your car on the left at the top of the hill after the pedestrian crossing. Along the ‘gap’ you will see Brigalow trees Acacia harpophylla with silvery foliage. This species has been cleared extensively in agricultural districts of southern Queensland. A walk up the path on the higher side of the road will take you to the top of ‘Sundial Hill’. The path goes past native pines, including the Bunya Pine Araucaria bidwillii and Hoop Pine Araucaria cunninghamii.
At the ‘Sundial of Human Involvement’ you can tell the time using your own body as the marker. Take a rest and enjoy the magnificent views across Campbelltown to the Royal National Park and the other way across to the Blue Mountains. If you are feeling fit, continue along the Central Valley Walk and up the zig-zag path to the summit of Mt Annan. Here the original dry rainforest species are being gradually regenerated and the African Olive and pepper tree weed species are being removed.
On both sides of the road going up the hill, you will see some Mallee’s — small multi-stemmed eucalypts. These are from arid parts of Western Australia and South Australia. Look on the left for the interesting orange-red buds on the popular Fuchsia Mallee Eucalyptus forrestiana and on the Square-fruited Mallee Eucalyptus tetraptera. On the right, going up the hill, you will see tall species such as Eucalyptus megacornuta and the very fine foliage of Eucalyptus angustissima and E. ceasia subsp, magna.
Bisectaria is the largest section in subgenus Symphyomyrtus, comprising about 270 taxa (species and subspecies). The vast majority are restricted to the Mediterranean climatic region of southwestern Western Australia, which is arguably the centre of origin and diversification for the group (although probably not possessing a 'Mediterranean' climate earlier in the history of the group). The deduced relationships of the taxa at the various levels lead strongly to the conclusion that the arid zone and eastern regions have been separately colonised on several occasions by members of different series, and several radiation and isolation events can be postulated (Hill 1989, 1990).
Brachychiton Arboretum: Kurrajongs
On the right after the Cypress Pines you will find a group of various trees which are grafted onto Illawarra Flame Tree rootstocks for reliability in our clay soils. One of these is the Little Kurrajong (Brachychidton bidwillii) which, as with most Kurrajongs, flowers on bare branches before the new leaves emerge. Within the Arboretum on the right hand side of the road, is the spectacular Illawarra Flame Tree (Brachychiton acerifolius). Further along are the fat trunks of Queensland Bottle Trees (Brachychiton rupestris). The trunk of these trees may reach 2 m in diameter and they have edible roots and seeds. The Brachychiton genus includes the Illawarra Flame Tree, the Bottle Tree, Kurrajong Tree and 28 other trees and shrubs. Generally drought tolerant once established Brachychiton species grow from 4m - 30m. Full sun and a well drained position Brachychiton are generally undemanding. Widely used in street plantings many species make great shade trees.
Callitris Arboretum: Cypress pines
About a half a kilometre further along on both sides of the road, is a grove of cypress pines (Callitris). All Callitris are native to Australia, except for two species which occur in New Caledonia. The Black Cypress Pine Callitris endlicheri is used extensively for timber, though it is not as durable and insect-resistant as the White Cypress Pine Callitris glaucophylla. The Northern Cypress Pine Callitris intratropica was used by Aborigines for the treatment of diarrhoea and as a mosquito repellent.
Casuarina: 9. Sheoaks
About 400m along you will see a number of Sheoaks around Lake Nadungamba (meaning ‘water of the flowers’ in the native Tharawal language). Sheoaks include casuarinas and allocasuarinas. They can be found near fresh or brackish water (e.g. the Swamp Oak Casuarina glauca) or in drier sandstone soils (e.g. Allocasuarina distyla). Sheoaks range in size from very small ground covers (e.g. Allocasuarina nana) to large trees (e.g. Casuarina cunninghamiana). Their name, which would now be considered insulting to women, is derived from the timber, which is oak-like in appearance but inferior in strength. After another 100 m you will pass the Woodland Picnic Area. C. cristata, C. cunninghamiana, C. cunninghamiana subsp cunninghamiana, C. cunninghamiana subsp cunninghamiana X glauca, C. glauca +grafts, C. pauper, C. equisetifolia, C. obesa, Allocasuarina media, A. distyla, A. rigida.
On the right you will see a group of trees clustered around the S-bend in the road. These eucalypts have recently been separated from the genus Eucalyptus and placed into a new genus of their own — Corymbia. The group includes Bloodwoods and Yellow Jackets, and many are from the tropics as well as eastern New South Wales and Queensland. Look for the Spotted Gum Corymbia maculata, which occurs naturally along the road to Appin, and the popular Lemon Scented Gum.
All species included here are part of section Dumaria, itself a component of the large subgenus Symphyomyrtus (Pryor & Johnson 1971, Brooker 2000). This section is substantially Western Australian in distribution. The section is characterised by the regularly inflexed filaments with cuneate anthers that are regularly closely packed with their apices appressed to the nectary disc in unopened buds. The group is otherwise highly diverse, and has so far not been clearly demonstrated to be monophyletic. A number of distinctive and clearly defined series are recognisable, however, within the section Dumaria (Table 1). Series Incrassatae, Torquatae, Leptocalyces and Obtusiflorae are discussed separately below.
Dyoblakea: Corymbia tessellaris
Section Blakearia (the 'ghost gums' or 'paper-fruited bloodwoods') is a distinctive, primarily tropical group of 27 species (Figs. 17, 93). The names 'Carbeen' and 'Moreton Bay Ash' have also been applied to species in this group. The group reaches maximum diversity in monsoon savannah woodlands of northern Australia from Queensland through the Northern Territory and the Kimberley region of Western Australia, with eight species extending south of the Tropic of Capricorn, three of these essentially eastern, two western and three central but with extension to the east and/or west. Three species also occur in southern parts of the island of New Guinea, one being endemic.
Eudesmia: Eucalypts from Western Australia
About 100m further on the right hand side close to an S-bend is a group of trees which are mainly mallees from Western Australia. The Tallerack Eucalyptus pleurocarpa has square, white stems and fruit and often juvenile leaves. The Inland Yellowjacket Eucalyptus similis has peeling, yellow bark. E. ebbonoesis, E. erythrocorys, E. eyreana, E. pallida, E. pleurocarpa, E. similis.
Exsertaria: Red Gums
This site has not been a success and is now prominently a mixture of native and introduced grass.
The 'Red Gums' are a complex group comprising four series, parts of series Albae and Brevifoliae being discussed here. The red gum group is difficult to diagnose, and not unequivocally monophyletic.
The most likely sister group to the red gums is section Transversaria, which shows similarities in seed coat structure, the proliferation of ovules on the placenta, and the subterminal hilum in some groups (although the latter is possibly a result of close packing caused by the increased number of rows of ovules).
The very thinly peeling bark leaving a powdery salmon or orange fresh surface is uniform in the two groups, and may be a synapomorphy, as may also the disjunct, petiolate, rounded juvenile leaves. The thickened inner calyptra is apomorphic in series Albae, although not clearly present in all species of the series. The thickened valves are also apomorphic in this series.
Maidenaria: Gum trees
In this arboretum you will find the Camden White Gum, Eucalyptus benthamii, which is a local tree of very limited distribution and is classified as a threatened species. Also growing here is Maiden’s Gum Eucalyptus maidenii which was named after Joseph Henry Maiden, who was the Government Botanist and Director of the Botanic Gardens in Sydney, 1896-1924.
Pedaria Eucalyptus brevistylis
Renantheria: Stringybarks and scribbly gums
Down the hill on the northern side of the road opposite the Bottlebrush Garden you will come to a group of eucalypts. These Stringybarks, Ashes, Scribbly Gums, Peppermints and Snow Gums come mainly from south-eastern Australia. As well as tall trees you will see Mallee’s — small, multi-stemmed eucalypts — such as the Whipstick Mallee Ash Eucalyptus multicaulis, from near Sydney, and the Faulconbridge Mallee Ash Eucalyptus burgessiana, which has a restricted range in the Blue Mountains.
Transversaria: Mahogany and Grey Gums
About 50m further along on the right hand side is another group of eucalypts. Coming mostly from moist, coastal environments, these trees are generally larger and have broader, greener leaves than trees from the arid parts of Australia. Many of the gums in this group have been commercially harvested for their timber.
The group Transversaria as defined here comprises 23 species such as E. propinqua, E. grandis, E. saligna, E. robusta, E. diversicolor, E. botryoides. Most species occur in tall, wet forests of the coast and ranges of eastern Australia, with one species in wet forests of southwestern Western Australia, one extending to New Guinea and three endemic to islands of southeastern Indonesia and East Timor.
Species of this group are abundant around Port Jackson, and were consequently recognised very early in the history of Australian botany. Four species were described before 1800 by Smith (1790, 1795, 1797). Nine species were recognised by Bentham (1867), in six different groups (six of these were species of Transversaria sens. strict., placed by him in three subseries of his series Normales). He also reduced E. punctata DC. to synonymy with E. tereticornis Sm.
Northocalyptus: Tallow woods
Located along the water canal at the northern most point Cunningham Drive, this arboretum consists of 1 species (Eucalyptus microcorys, Tallowwood). Tallowwood is one of the best hardwoods in Australia. It is classified in a section of its own as it is not closely related to other eucalypts.