Tree to 8 m tall or shrub (marlock) with single stem branching low. Lignotuber absent.
Bark smooth throughout, whitish and grey.
Branchlets lacking oil glands in the pith.
Juvenile growth (coppice or field seedlings to 50 cm): not seen
Adult leaves alternate, petioles 0–1.2 cm long; blade elliptical to oblong or obovate, 4–9 cm long, 1–3 cm wide, base tapering to petiole, margin entire or distantly notched (?lenticels present), apex rounded and mucronate to pointed, concolorous, mid-green, slightly glossy, side veins acute, reticulation moderate and broken, intramarginal vein remote from margin and sometimes with a second vein close to margin, oil glands scattered, intersectional.
Inflorescences axillary unbranched, peduncles broad strap-like, 3–7 cm long; buds (?11)15–21 or more per umbel, pedicels absent. Buds syncarpous (all of the buds in a cluster are completely joined by the hypanthium only, the upper part of each bud remains free, at maturity the combined length of the fused part plus operculum is ca 3-4.5 cm, whilst width of individual buds measured at the base of the operculum is 0.8–1.8 cm); scar present but may become obscure late in bud development, operculum stoutly horn-shaped ca 4–6 times as long as the fused part of the bud, stamens erect, long, anthers narrowly oblong, versatile, dorsifixed, dehiscing by longitudinal slits, style long and straight, stigma blunt, locules 3, the placentae each with (?6)–8 vertical rows of ovules; flowers green to yellow-green.
Fruit on stout down turned-peduncles, syncarpous, the individual capsules in the woody mass 1.4–2.6 cm wide, length not measurable, dehiscing by elliptical holes formed as the 3 valves split along the sutures but remain connected apically, disc covers the entire surface of the valves.
Seed blackish brown, 2–4 mm long, angularly ovoid to cuboid, dorsal surface shallowly reticulate, hilum ventral to terminal.
Cultivated seedling (measured at ca node 10): cotyledons coarsely Y-shaped to bilobed; stems triquetrous when young but becoming rounded in cross-section, densely scabrid; leaves always petiolate, opposite for 3 to 5(7) nodes then alternate, orbicular to ovate or deltoid, sometimes broadly elliptical, 3–8 cm long, 2–7 cm wide, base truncate to rounded or tapering, apex usually rounded, margin wrinkled and indented, green, scabrid; scabridity is due to bristle-glands with stellate apices which are most prominent on stems, petioles, leaf margins and veins on underside of lamina but only sparse on lamina generally.
A small mallet (tree) or shrub endemic to Western Australia, of coastal distribution from Two Peoples Bay east to beyond Esperance and the islands of the Recherche Archipelago. The bark is smooth and the leaves glossy light green with acute venation. The buds and fruit form conspicuous clusters in the crown.
Eucalyptus conferruminata belongs in Eucalyptus subgenus Symphyomyrtus section Bisectae subsection Hadrotes because the cotyledons are coarsely Y-shaped, buds have an operculum scar, a long (inner) operculum and erect stamens, fruit are large, thick-rimmed and held rigidly. Of the ten species in subsection Hadrotes eight lack oil glands in the pith of the branchlets and have scabrid seedlings. Together these eight species form series Lehmannianae, a group further characterized by having fruit with exserted valves that remain fused at their tips after seed shed, a feature shared with the more distantly related E. cornuta.
Of the eight species in series Lehmannianae four, E. conferruminata, E. lehmannii, E. mcquoidii and E. arborella, have the buds (and fruit) in each axillary cluster fused basally whilst the other four species, E. newbeyi, E. burdettiana, E. talyuberlup, and E. megacornuta, have buds and fruit free.
E. conferruminata is distinguished from its three near relatives by its stoutly horn-shaped opercula only ca 5 times as long as wide. E. lehmannii, E. mcquoidii and E. arborella all have much longer and more slender opercula. E. lehmannii is further distinguished by being a mallee and E. mcquoidii by having terete, not flattened, peduncles and up to ca 50 buds per cluster (cf. up to 21 buds for the other three species).
Flowering has been recorded in October.
Widely grown as a street tree, farm windbreak and garden specimen. Famous for its balls of green to yellow-green flowers. In the Botanic Gardens in Cape Town, South Africa, specimen trees attain 15 metres in height.
Hussey et al (1997) state that Eucalyptus conferruminata has become naturalized in areas away from its natural distribution in Western Australia. In Victoria Carr et al. (1992) regard this species as an environmental weed posing a potential risk to heath and associated woodlands, stating that it is currently rare or localized in small populations.