Eucalyptus balladoniensis subsp. balladoniensis

Balladonia mallee

Eucalyptus | Symphyomyrtus | Bisectae | Destitutae | Balladonienses

Eucalyptus balladoniensis Brooker, Nuytsia 2: 103 (1976) subsp. balladoniensis.

T: 80 km by road S of Zanthus, W.A., 31° 37'S, 123° 53'E, 13 Feb. 1970, M.I.H.Brooker 2471; holo: PERTH. [The locality and collector number may well be in error. The reader is directed to Telopea 4: 614 (1992) for further information.]

Mallee to 5 m tall. Forming a lignotuber.
Bark rough, firm (compacted), fibrous to flaky on lower half of stems, dark grey, then shedding in short ribbons above to show smooth grey-brown to pink-brown bark.
Branchlets lacking oil glands in the pith.
Juvenile growth (coppice or field seedlings to 50 cm): stems rounded in cross-section; juvenile leaves sessile to shortly petiolate, alternate, linear to narrowly lanceolate, 8–15 cm long, 0.6–2 cm wide, dull, grey-green.
Adult leaves alternate, petioles 1.2–2.5 cm long; blade lanceolate, 7–13.5 cm long, 1–2.7 cm wide, base tapering to petiole, margin entire, apex acute, dull, bluish green at first maturing glossy, green, side-veins at an acute or wider angle to midrib, reticulation moderate to dense, intramarginal vein close to margin, oil glands intersectional and island.
Inflorescences axillary unbranched, peduncles erect when young but down-turned at bud maturity, 1–2 cm long, buds 7 per umbel, pedicellate (pedicels 0.5–1.1 cm long). Mature buds more or less truncate-globose but with a coarsely beaked operculum, 1.9–2.5 cm long, 0.9–1.1 cm wide, scar present, operculum with robust almost cylindrical blunt beak which is less noticeable close to flowering time, stamens inflexed, anthers globular to oblong, versatile, dorsifixed, dehiscing by short slits, style long and straight, stigma blunt, locules 3 to 5, the placentae each with 4 vertical rows of ovules. Flowers pale yellow.
Fruit pedicellate (pedicels 0.6–1.6 cm long), hemispherical to truncate-globose, 0.7–1.1 cm long, 1–1.4 cm wide, disc descending, valves 3 to 5, with exserted  fragile style remnants.
Seeds grey-brown, 1.5–3 mm long, ovoid to flattened-ovoid, dorsal surface smooth, hilum ventral.

Cultivated seedlings (measured at ca node 10): cotyledons Y-shaped (bisected); stems rounded, square, or in some, apparently 5-sided in cross-section; leaves sessile to subsessile throughout, opposite for ca 5 nodes then becoming sub-opposite to alternate or spirally arranged, linear, 2–3.5(7) cm long, 0.2–0.4(0.7) cm wide, dull, grey-green.

Flowering has been recorded in April, July, August, October and November.

Eucalyptus balladoniensis is a mallee species endemic to Western Australia, distributed from the Balladonia area south-west towards Mt Ney and Mt Ridley. It grows in dry woodlands preferring sandy rises or calcareous sandy loams. It has rough bark and slightly glossy, green leaves. Bud clusters are spreading to pendulous. Buds are obese and the operculum is conspicuously contracted in the upper part to form a broad beak.

In the classification of Brooker (2000) E. balladoniensis belongs in Eucalyptus subgenus Symphyomyrtus section Bisectae subsection Destitutae because buds have two opercula, cotyledons are Y-shaped and branchlets lack oil glands in the pith. Within this subsection it is related closely to only one other species, E. indurata, the two species forming series Balladonienses. Both species have rough bark, flaky to fibrous and more or less compacted in E. balladoniensis and hard, compacted in E. indurata. Adult leaves are slightly glossy in E. balladoniensis and very glossy in E. indurata. E. balladoniensis has more bluntly and stoutly beaked opercula and larger buds and fruit. Both species have yellow flowers.

There are two subspecies:

E. balladoniensis subsp. balladoniensis
With distinctly pedicellate buds and fruit; with a wide distribution to the south of the Eyre Highway.

E. balladoniensis subsp. sedens
Has more or less sessile buds and fruit, pedicel if present very short; distributed only north of Balladonia towards Zanthus.

Eucalyptus balladoniensis: from the locality of Balladonia.

subsp. sedens: Latin sedens, sitting, referring to the sessile buds.