My very favourite place in Queensland is Isla Gorge. An area of 5,000 hectares was declared as National Park in 1964 and in 1983 the park was extended to 7,800 hectares. The main feature of the park is the sandstone gorge system formed by Hewitt and Gorge Creeks and their tributaries.
Isla Gorge is the most accessible of the central Queensland sandstone gorges, and yet it is one of the most infrequently visited. It is just 35 Km south-south-west of Theodore or 60 Km north of Taroom. The Leichhardt Highway forms the eastern boundary of the park, and the superb lookout is just a kilometre from the highway. I find the whole area absolutely fascinating, partly because of the scenic grandeur, but even more because of the great diversity of the flora. I am sure whole chapters could be written about the species of shrubs, herbs, ferns, grasses etc., so I propose to restrict my ramblings to the tree flora.
A. EUCALYPTS.
The great bulk of the park is covered by open eucalypt woodland; 10-15 metres high on the ridges, 20-30 metres high in the valleys. Considering the relatively small size of Isla Gorge National Park, it contains an amazing range of Eucalyptus species. There are at least twenty species, including four which are not yet formally named. Here are some brief notes on them:-
E. tessellaris (Moreton Bay Ash) - grows in the valleys near the creeks, but not very common. A graceful and adaptable tree.
E. polycarpa (Long-fruited Bloodwood) - at the southern and northern ends of the park, on lower slopes. Bark grey, persistent to twigs, chunky.
E. erythrophloia (Red-barked Bloodwood) - grows on heavier soils on hill- sides at the northern end of the perk. Southern limit of species at this longitude.
E. sp. aff. polycarpa (Sandstone Bloodwood) - common on the sandstone ridges. Flowers January. Fruits large and broad. Small branches smooth.
E. watsoniana (Large-fruited Yellow Bloodwood) - a common tree on the sandstone ridges end slopes. Attractive yellow, flaky bark and large grey-green leaves. Flowers May-September with mushroom-like buds. This is an excellent species for cultivation on a wide range of soils.
E. trachyphloia (Brown Bloodwood) occurs on the sandstone ridges, not very common. Small ovoid fruits. Bark grey to yellowish, rough except on small branches. A very drought tolerant tree.
E. maculata (Spotted Gum) - quite a large tree on the lower slopes and valleys. Smooth pink bark. Common.
E. cloeziana (Gympie Messmate) - commonly seen both on the ridge-tops and in the valleys, where it may achieve 25 metres in height. Bark crocodile pattern, grey-yellow in colour. Small and medium branches smooth. Leaves not pendulous, buds and fruits in clusters. A useful, fast growing shade tree, adaptable in cultivation.
E. baileyana (Baileys Stringybark) - sandstone slopes. Bark fibrous, black, interlaced. Fruits large and globular. Moderate sized tree of good form with a lacy canopy. Relatively uncommon. A truly beautiful tree, suited to any well drained site.
E. tenuipes (Narrow-leaved Mahogany) - a very common tree around the lookout area and throughout the park on sandstone ridges. A small, stunted tree, with grey-brown fibrous bark, hemispherical fruits, 6 mm across.
E. rubiginosa (Woollybark) - on weathered sandstone slopes. Found throughout the park, but uncommon. Bark fibrous to woolly, orange to rusty coloured. Leaves pale green, fruit hemispherical, about l0 mm across. A rare species.
E. acmenoides (White Mahogany) - moderate sized tree on steep slopes in the more sheltered gullies. Bark grey, fibrous. Fruit small, ovoid.
E. longirostrata (Inland Grey Gum) - a tall, straight-trunked tree growing just above the creeks. Bark smooth, generally grey in colour, but orange in summer. Leaves non-pendulous, discolorous. Quite common. A Fast growing tree suitable for most soil types. More drought tolerant than other grey gums and other shade-giving gums.
E. tereticornis (Forest Red Gum) - large tree growing next to the creeks. Bark smooth, white, bluish or grey. Common and hardy.
E. microcarpa (Grey Box) - grows only on the south-western edge of the park on heavy clay soils. Thin scaly bark on the trunk, smooth and grey above.
E. fibrosa ssp. nubila (Blue-top Ironbark) - grows along the highway at the southern end, as far as the lookout turnoff. Leaves broad and silvery, distinctly stalked.
E. melanophloia (Silver-leafed Ironbark) - grows on the south-western edge of the park, and at the northern end, on loamy to clayey soil. Leaves are opposite, stalkless and silvery.
E. sp. aff. crebra - an Ironbark. Common throughout the park, except on the sandstone ridges. Similar to Narrow-leafed Ironbark, but the leaves are broader and the fruits are larger.
E. sp. aff. decorticans (Breakaway Ironbark) - a rare species growing on the edges of the escarpments. Leaves narrow, grey. Fruits small with exserted valves. Bark rugged, furrowed. Small branches smooth and white.
E. sp. aff. paniculata - an Ironbark. The most common ironbark of the sandstone ridges. Bark rugged and black, small branches smooth. Leaves green. Seedling leaves green and shiny.
B. NON-EUCALYPTS.
(a) Sandstone ridges and slopes.
Angophora leiocarpa (Smooth-barked Apple) is a common small tree with smooth pink bark. It resembles the Spotted Gum, but A. leiocarpa is usually of poor form and has thin, ribbed fruits.
Lysicarpus ternifolius (Tom Russell's Mahogany) - a very common tree with grey fibrous bark and dark green, needle-like leaves in whorls. It bears white flowers like a Leptospermum in Spring.
Leptospermum trinervium - a large shrub or small tree growing on ridges. Leaves quite silvery. Flowers white.
Persoonia falcata (Northern Geebung) - a small tree to five metres high with rough grey bark and grey-green falcate leaves. The 4-petalled yellow flowers are very showy and flowering reaches a peak in November. Fruit is a green drupe. This species occurs widely across northern Australia, but is uncommon south of the tropics, and reaches its southern limit at Isla Gorge. It should be a wonderful garden plant, though it could be difficult to propagate.
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| Xylomelum pyriforme |
Xylomelum pyriforme (Woody Pear) - a small tree with rough, flaky bark. Mature specimens inconspicuous unless the large woody pear-like fruits are seen. Presence is usually betrayed by the sharply toothed juvenile leaves. Flowers white, in spikes, like miniature Macadamia flowers. Slow growing, but worth cultivating for the unusual woody seed pods.
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| Grevillea longistyla |
Grevillea longistyla - a sparsely foliaged shrub or small tree with narrow grey eaves and racemes of brilliant red flowers. It is common on the ridges and flowers mainly in spring. It is an adaptable and beautiful plant for Queensland gardens.
Allocasuarina inophloia (Threadybark Sheoak) - a lovely small tree to 8 metres on the broad ridge tops. The plume-like foliage is dark green, while the rusty coloured male flowers (occurring in winter) provide a wonderful contrast. However, it is the warm brown, deeply shredded, fibrous bark that is exceptional and unique in the genus.
Acacia crassa - small tree, long curved phyllodes, flowers in 'catkins'.
Acacia leptostachya - shrub or small tree, very common on the sandstone ridges at Isla. Silvery phyllodes, flowers in catkins.
Acacia falciformis - large tree, dark rough bark, white ball flowers, on the slopes.
Acacia penninervis - small tree, white ball flowers in summer, on ridges.
Acacia neriifolia - small tree, narrow green phyllodes, yellow ball flowers.
Acacia complanata - shrub to small tree, flat stems, yellow ball flowers.
Petalostigma pubescens - a shrub to small tree, common on slopes and ridges. Leaves small, furry. Fruit globular, red to orange.
Astrotricha pterocarpa - barely in the tree category, but included in view of its bizarre appearance. It is a conspicuous plant of the upper sandstone slopes, being an unbranched shrub to 4 metres high. The leaves are large and furry, and the flowers small but numerous, at the top of the plant. It would be an interesting garden subject.
(b) Lower hill slopes with deeper soil
Grevillea striata (Beefwood) - a moderate sized tree with silvery straplike leaves. Widespread in Queensland, but uncommon at Isla.
Hakea lorea (Bootlace Oak) - a small tree with rough bark and pendulous very long, terete leaves. Flowers white, in spikes.
Erythrina vespertilio (Bats-wing Coral Tree) - a small tree with corky bark, leaves shaped vaguely like a bats wings, end large red pea flowers.
Brachychiton populneus (Kurrajong) - a common tree with bell-shaped flowers and lobed leaves. Readily cultivated, but rather slow growing.
Alphitonia excelsa (Soapy Ash) - a common small tree with white bark and leaves which are green above and white below.
Caelospermum reticulatum - a shrub to small tree with corky bark and pale green, very stiff leaves. Unattractive.
(c) Rainforest
On the more fertile soils and where moisture levels are slightly greater, eg. near creeks or on a southerly aspect, some very nice patches of 'dry' rainforest occur. These rainforests are dominated by the two types of Bottle Tree (Brachychiton rupestris and B. australis), but there are dozens of other tree species. The majority of these are listed below:
Acacia fasciculifera (Scrub Ironbark)
Acacia harpophylla (Brigalow)
Alectryon connatus
Alstonia constricta (Quinine Tree)
Atalaya salicifolia (Whitewood)
Austromyrtus bidwillii (Python Tree)
Backhousia angustifolia (Curry Bush)
Canthium coprosmoides
Capparis loranthifolius
Cassia tomentella (Velvet Cassia)
Croton insularis (Cascarilla Bark)
Diospyros humilis
Drypetes deplanchei (Yellow Tulip)
Elattostachys xylocarpa (White Tamarind)
Erythroxylum australe
Euroschinus falcata (Ribbon Wood)
Excoecaria dallachyana (Blind-Your-Eye)
Exocarpos latifolius (Native Cherry)
Flindersia australis (Crows Ash)
Flindersia collina (Leopard Ash)
Geijera parviflora (Wilga)
Glochidion ferdinandi (Cheese Tree
Lysiphyllum sp.
Mallotus philippensis (Red Kamala)
Melia azedarach (White Cedar)
Notelaea microcarpa
Owenia venosa (Crows Apple)
Pavetta australiensis
Pouteria cotinifolia
Siphonodon australis (Ivorywood)
Turraea pubescens
Gullies and Creek beds.
In the sheltered gullies near the lookout one can readily come across Turpentine (Syncarpia glomulifera). This is a coastal forest tree, and the isolated occurrence at Isla Gorge is quite remarkable - a reminder that climatic conditions in Queensland were at one time much wetter. It grows to 25 metres here, has stringy grey bark and the fruit is a fused capsule. To see some, merely walk 30 metres west from the sign near the highway which says "Gorge Lookout 1.4 Km".
Further downstream, in the creek beds, Melaleuca linariifolia (Snow-in-Summer) is dominant. Other creek dwellers are Acacia glaucocarpa, Lophostemon suaveolens (Swamp Box), Angophora floribunda (Rough-barked Apple), Ficus spp. (Figs) and Casuarina cunninghamiana (River Oak).
(EDITORS NOTE: Isla Gorge was one of the areas visited during the Pre-Conference Tour to Carnarvon Gorge, from 21st to 27th September 1985. This was a very interesting and exciting bus trip, providing outstanding scenery and a great variety of plant life.)
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