Eucalyptus incerata

Eucalyptus | Symphyomyrtus | Bisectae | Glandulosae | Erectae | Abundae

Eucalyptus incerata Brooker & Hopper, Nuytsia 14: 347 (2002).

T: 16.1 km N of Hyden – Norseman track on Mt Day road, 32°04'S, 121°02'E, 7 Nov. 1983, M.I.H.Brooker 8358, S.D.Hopper, L.A.S.Johnson & D.F.Blaxell); holo: PERTH, iso: AD, CANB, MEL, NSW.

Mallee to 5 m tall. Forming a lignotuber.
Bark smooth throughout, light grey-brown over orange.
Branchlets glaucous; oil glands present in the pith.
Juvenile growth (coppice or field seedlings to 50 cm): not seen.
Adult leaves thick, alternate, petioles 0.5–1.7 cm long; blade lanceolate, 5–10.5 cm long, 1–3.2 cm wide, base tapering to petiole, margin entire, apex pointed, concolorous, glaucous at first but maturing glossy, green, surface appearing "glazed", side-veins acute or obscure, reticulation not visible, intramarginal vein present or obscure, oil glands numerous.
Inflorescence axillary unbranched, pendulous, peduncles flattened, 1.5–3.5 cm long, buds 7 per umbel, pedicellate (pedicels 0.7–1.2 cm long). Mature buds elongated, 2.2–3.5 cm long, 0.6–0.9 cm wide (asymmetrically fusiform), glaucous, scar present (outer operculum shed early), operculum bluntly horn-shaped, ca 2–2.5 times the length of the hypanthium, stamens erect, anthers oblong, versatile, dorsifixed, dehiscing by longitudinal slits, style long and straight, stigma rounded, locules 4, the placentae each with 4 vertical rows of ovules. Flowers yellow.
Fruit down-turned, pedicellate (pedicels 0.6–0.9 cm long), stoutly barrel-shaped to cupular, 1–1.5 cm long, 0.9–1.8 cm wide, disc descending, obscured by persistent staminophore, valves 4, held at rim level.
Seeds dark brown, 0.7–2 mm long, ovoid to flattened-ovoid, dorsal surface shallowly reticulate, hilum ventral.

Cultivated seedlings (measured at node 10): cotyledons Y-shaped (bisected); stems rounded in cross-section, usually glaucous; leaves always shortly petiolate, opposite for 3 to 6 nodes then alternate, lanceolate to ovate, 5.5–9.5 cm long, 2.5–3.5 cm wide, dull, green to faintly glaucous. Leaves at lowest 3 nodes sparsely warty especially on the midrib and may feel slightly rough when fresh.

Flowering has been recorded in October.

A mallee endemic to Western Australia, restricted to the Mt Day area between Hyden and Norseman. The bark is smooth and the branchlets, buds and fruits glaucous.

Eucalyptus incerata belongs in Eucalyptus subgenus Symphyomyrtus section Bisectae subsection Glandulosae because the buds have an operculum scar, cotyledons are bisected and branchlets have oil glands in the pith. Within this large subsection (ca 80 species) E. incerata is closely related to a group of mallees and mallets (series Erectae subseries Abundae) recognised by the glazed leaf surface, leaves with a great density of oil glands that obscures the venation, peduncles long and flattened, inflorescences spreading and buds with a long operculum and erect stamens.

The 14 species in subseries Abundae are loosely grouped as follows. There are five species here considered to form the E. eremophila group—E. depauperata, E. eremophila, E. incerata, E. tenera and E. tephroclada. All have non-ridged buds and fruit, which separates them from the following species,  E. goniocarpa, E. platypus, E. utilis, E. mimica, E. steedmanii and E.  alipes. E. suggrandis , whilst generally non-ridged, has much smaller buds than the five species of the E. eremophila group, and has warty opercula. E. spathulata and E. orthostemon also have non-ridged small buds very narrowly linear leaves.

The five species in the E. eremophila group are segregated by size of buds and fruit and presence and absence of white wax on stems, leaves, buds and fruit. E. incerata and E. eremophila have the largest buds and fruit. 

E. incerata differs from E. eremophila in having a lignotuber, i.e. it is a mallee, not a mallet, and in having heavily glaucous branchlets, buds and fruit, and in its restricted distribution. The non-glaucous E. eremophila occur to the east of the southern wheatbelt and is the only species in the group to extend into desert areas.

Two mallee species, the non-glaucous E. tenera and the slightly waxy E. tephroclada have very similar slender buds and fruit that are generally smaller than found in typical E. eremophila and E. incerata. The only difference between E. tenera, which is widespread in the southern and central wheatbelt, and E. tephroclada, more restricted to the Hyden-Southern Cross area, is the presence of white wax on branchlets, buds and fruit of the latter.

The fifth species, E. depauperata, is a slender non-glaucous whipstick mallee "distinguished within the E. eremophila group by the small leaves, buds and fruits" (Hill & Johnson, 1991), which, even at its type locality south-east of Lake King, grows with plants that look more like E. tenera.

Whilst the five species that now make up the E. eremophila group are included in this edition of EUCLID it is not always possible to assign individual plants to one or other of the names with certainty. 

Eucalyptus incerata: Latin inceratus, meaning covered with wax.