Cooktown Ironwood I ronwood

Erythrophleum chlorostachys (F. Muell.) Baill.

Cooktown ironwood is a medium-sized tree, often poorly formed and short-boled, attaining a height of 18 m and a diameter of 1 m. The stem is not buttressed. Some trees may be deciduous in the dry season. All parts of the plant are highly poisonous.

Cooktown ironwood has a wide distribution across northern Australia from north-eastern Queensland to the Kimberley area of Western Australia, with outliers in the Great Sandy Desert and a collection from the De Grey River in the Pilbara region; also on numerous offshore islands throughout its range from the Kimberley to Torres Strait.

This tree grows on a wide variety of soil and rock types. It grows on rocky hillsides but probably reaches its best development on creek and river flats.

Cooktown ironwood is usually a component of the open forests and woodlands and because it occurs over such a large area it is associated with a large number of eucalypts.

Related species: There are no other species of Erythrophleum in Australia but the genus occurs in Africa and Asia.

Publication: Hist. Pl. 2, 150 (1870). Type: Burdekin River area, north-western Queensland, F. von Mueller.

Names: Botanical—Erythrophleum, Greek erythros (red), phloios (bark), probably in reference to the red colour of freshly cut bark; Greek chloros (green), stachys (spike), referring to the greenish inflorescence. Common—alludes to its very hard wood and its occurrence near Cooktown, Queensland.

Bark: Hard, dark, rough and flaky or tessellated.

Leaves: Cotyledons—orbicular, about 1 X 0.8 cm. Seedling— alternate, paripinnate with two hair-like stipules about 0.2 cm long at the base of the hairy rhachis, about 3-5 opposite pairs of leaflets, entire, petiolules 0.1-0.2 cm long; leaflets, ovate-oblique, 1-2.5 X 0.5-1.5 cm, margins ciliate, midrib hairy, both surfaces with some scattered hairs on the leaf blades, green, discolorous, nervation not clearly visible on older leaflets but conspicuous on newer leaflets. Adult—spirally arranged, bipinnate, leaflets alternate, unequal-sided, obliquely orbicular to ovate, 3.5-5.3 X 2.5-5 cm, petiolules 0.2-0.4 cm long; lateral veins of leaflets in 6-11 pairs.

Inflorescences: Upper axillary spikes or panicles of spikes. Flower buds small and globular. Flowers sessile or subsessile, 5-merous, creamy green. Calyx lobes about 0.5-1 mm long, margins pubescent. Petals about 0.3 X 0.1 cm, margins pubescent. Stamens 10, filaments about 0.8 cm long. Ovary stalked, 1-celled, containing 4-8 ovules, style about 0.2 cm long, stigma small. Flowers are larger and distinctly pedicelate in the Broome-Dampier Downs area. Flowers Sept.-Dec.

Fruits: Flat legumes about 10-14 X 2.5-4 cm containing 1-8 flat seeds about 1 cm diameter.

Wood: Sapwood susceptible to Lyctus attack; heartwood red, very hard, tough and strong, very durable when exposed to the weather and also in the ground. One of Australia's densest timbers with a density of 1180 kg m-3 and has low shrinkage similar to teak (Tectona grandis). Resistant to termite attack.

Very suitable for railway sleepers and similar needs where strength and durability are prime requisites.

Climate: Altitudinal range: 100-1000 m; Hottest/coldest month: 30-39°C/13-22°C; Frost incidence: low; Rainfall: 3001700 mm per year, summer max.

Distinctive features: Dark rough bark, bipinnate leaves, creamy green flowers in spikes, flat legume, very hard and dense heartwood.

Erythrophleum chlorostachys 1. Adult leaves 2. Adult leaves and inflorescence 3. Seedling 4. Fruit 5. Flowers (S.E.M.) 6. Flower (S.E.M.) 7. Tree, near Atherton, Qld 8. Bark

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