Eucalyptus gigantangion

Kakadu woollybutt

Eucalyptus | Eudesmia | Reticulatae | Miniatae | Inclinatae

Eucalyptus gigantangion L.A.S.Johnson & K.D.Hill, Telopea 4 (2) 322 (1991).

T: Northern Territory: Twin Falls, Kakadu National Park, 13° 18’ S 132° 51’ E, C.Dunlop 6722 & G.Wightman, 16 July 1984; holo: NSW; iso: DNA.

Tree to 30 m tall. Forming a lignotuber.
Soft fibrous rough bark over most of the trunk, rough bark orange-brown to red-brown to dark grey or black. Upper trunk and large branches with white smooth bark. Branchlets not glaucous, oil glands present in the pith.
Juvenile growth (coppice or field seedlings to 50 cm): stems rounded in cross-section, hairy; juvenile leaves opposite or alternate, petiolate, ovate to broadly lanceolate, 5.5–11 cm long, 2.5–5 cm wide, base rounded to truncate to tapering to the petiole, apex acute, dull blue-green to green, with stellate hairs.
Adult leaves alternate petioles 1–2 cm long; blade narrowly lanceolate, 6–16 cm long, 1–2 cm wide, base tapering to petiole, discolorous, dull green to blue-green, side-veins at a wider angle than 45° to the midrib, reticulation dense, intramarginal vein present and very close to the margin, oil glands intersectional.
Inflorescence axillary single, peduncles 1.8–2.5 cm long, buds 7 per umbel, sessile to shortly pedicellate, pedicels 0–0.1 cm long. Mature buds fusiform, (2.2–2.8 cm long, 1–1.4 cm wide), not glaucous, calyx fused to the corolla and evident as 4 small teeth at the apex of the bud, hypanthium longitudinally striated or ribbed, operculum conical, stamens irregularly flexed, anthers oblong, versatile, dorsifixed, dehiscing by longitudinal slits (non-confluent), style long, hooked or bent beneath the apex of the bud, stigma tapered, locules usually 3, the ovules usually arranged in 6 distinct vertical rows on the placentae. Flowers orange.
Fruit sessile, urceolate, longitudinally ribbed, 3.5–5.8 cm long, 2.2–5 cm wide, not glaucous, disc vertically to obliquely descending, valves 3, enclosed.
Seeds dull dark grey to black, ± flattened to obliquely pyramidal to ± cuboid, 4–7 mm long, ventral surfaced ribbed, dorsal surface smooth, hilum ventral.

Cultivated seedlings (measured at node 10): cotyledons reniform to bilobed; stems round in cross-section, hairy, leaves petiolate, opposite, broadly lanceolate, 7–11 cm long, 2.5–3.5 cm wide, blue-green to green, apex acute, base rounded to tapering to the petiole, lamina hairy on both sides, margins sometimes appear toothed due to the hairs.

Flowering has been recorded in July and August.

A medium-sized to tall tree, restricted to the Kakadu National Park and north-western Arnhem Land in the Northern Territory. It is characterised by its rough, papery or fibrous bark on the trunk and the smooth, white bark on the upper trunk and branches, the discolorous, narrowly lanceolate adult leaves, the non-glaucous buds, the bright orange filaments of the flower and the large, ribbed, urceolate fruit.

It belongs to the taxonomically complex subgenus Eudesmia and is included in section Reticulatae, series Miniatae, subseries Inclinatae characterised by having the calyx fused to the corolla and evident as four small teeth at the apex of the bud, hairy seedlings, adult leaf reticulation relatively dense, buds with a long style and bright orange flowers. It is closest to E. miniata, a common species right across the top of Australia from the Kimberley to just across the Queensland border, and to E. chartaboma from the Croydon to southern Cape York Peninsula area of north Queensland. Both are members of the subseries Inclinatae. E. miniata can be distinguished by its broader adult leaves and its glaucous branchlets, buds and fruits (adult leaves in E. miniata 2–4.5 cm wide and in E. gigantangion 1–2 cm wide). E. chartaboma is weakly distinguished by its paler, flaky, papery yellow-brown to pink-brown rough bark and its glaucous branchlets, buds and fruit (E. gigantangion not glaucous).

E. phoenicea and E. ceracea, two other members of the subseries Inclinatae, are relatively close to E. gigantangion. E. phoenicea can be distinguished by normally having more than 15 buds to each umbel and by having narrower cylindrical to urn-shaped fruit to 1.3 cm wide. (E. gigantangion has seven-budded umbels and large fruit, always wider than 2.2 cm.) E. ceracea can be distinguished by consistently having a mature crown of glaucous, ovate juvenile leaves.  

Eucalyptus gigantangion: Greek gigant, a giant and aggeion, a vessel or receptacle, referring to the large fruit.