Eucalyptus erythronema subsp. inornata

Yellow-flowered mallee

Eucalyptus | Symphyomyrtus | Bisectae | Glandulosae | Elongatae

Eucalyptus erythronema subsp. inornata D.Nicolle & M.E.French, Nuytsia 22(6): 461-462 (2012).

T: Western Australia: south of the York to Quairading Road, [precise locality withheld for conservation reasons], 12 Nov. 2000, D. Nicolle & M. French DN 3685; holo: PERTH 05783283; iso: CANB.

Mallee or tree to 6 m tall. Forming a lignotuber.
Bark smooth throughout, dark satiny pink-brown to dark red, shedding in thin sheets to reveal powdery creamy-white.
Branchlets usually not waxy (non-glaucous); oil glands present in the pith.
Juvenile growth (coppice or field seedlings to 50 cm): not seen.
Adult leaves alternate, petioles 0.5–1.5 cm long; blade lanceolate to narrowly so, 5–8.5 cm long, 0.8–1.5 cm wide, base tapering to petiole, margin entire, concolorous, olive-green to green, glossy, apex pointed, side-veins acute, reticulation sparse or obscure, broken, intramarginal vein present, oil glands very numerous, island, more or less round.
Inflorescence axillary unbranched, pendulous, peduncles rounded in cross-section, 1.5–2.5 cm long, buds 3(7) per umbel, long-pedicellate (pedicels 0.8–1.7 cm long). Mature buds broadly fusiform (1.4–1.8 cm long, 0.7–0.9 cm wide), non-glaucous, scar present (outer operculum shed very early), inner operculum conical to beaked, a few outer stamens fully erect but most stamens variably to fully inflexed, anthers oblong, versatile, dorsifixed, dehiscing by longitudinal slits, style long and straight, stigma blunt to tapered, locules 4 or 5, the placentae each with 6 vertical rows of ovules; operculum sheds at flowering leaving a conspicuous broad vertical scar. Flowers creamy yellow.
Fruit on down-turned peduncles, pedicellate (pedicels (0.8)1–1.7 cm long), obconical, 0.8–1.1 cm long, 1–1.2 cm wide, smooth or weakly ribbed, disc usually level to gently descending, valves 4 or 5, rim level to scarcely exserted.
Seeds brown, 0.5–1.5 mm long, ovoid to flattened ovoid, dorsal surface clearly and shallowly reticulate, hilum ventral.

Cultivated seedlings (measured at node 10): cotyledons Y-shaped (bisected); stems rounded in cross-section; leaves always petiolate, opposite for 4 to 6 nodes then alternate, lanceolate, 6.5–13 cm long, 1.2–3.5 cm wide, dull, green to grey-green.

Flowering has been recoded in August, September and October.

Eucalyptus erythronemais an erect mallee species endemic to Western Australia, found in the wheatbelt from Wyalkatchem south to Pingaring and east to Bullfinch. The bark is very attractive, varying seasonally from powdery white to dark satiny reddish and pink-brown. The adult leaves are glossy, olive-green to green with all but the mid-rib, side-veins and intramarginal vein obscured by oil glands. Buds and fruit are pendulous in the crown.

In the classification of Brooker (2000) E. erythronema 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. erythronema is closely related to a group of mallees and mallets (series Elongatae ) recognised by the glossy green leaves with many oil glands obscuring the reticulation but not the main side-veins, buds with very long conspicuous pedicels, short broad opercula, inflexed stamens and ovules in 6 vertical rows. There are five species in series Elongatae—E. cylindriflora, E. cerasiformis, E. dielsii, E. armillata and E. erythronema (with two subspecies).

The taxonomy of E. erythronema has recently been revised by Nicolle & French (2012) resulting in the three taxa compared below. All three taxa have highly distinctive pendulous buds and fruit.

E. erythronema subsp. erythronema
Buds at least weakly waxy, flowers red; branchlets conspicuously white waxy (glaucous). The buds and fruits are not flanged, and ribbing, if present at all, is weak. It occurs in the central wheatbelt from Wyalkatchem south-east to Hyden and extending east into the drier areas towards Bullfinch. Occurs on a variety of sandy to loamy well drained soils on slightly rising ground (see Nicolle & French, ibid.). (Formerly E. erythronema var. erythronema in part). 

E. erythronema subsp. inornata
Buds not waxy, flowers creamy yellow; branchlets usually not waxy (non-glaucous). The buds and fruits are not flanged, and ribbing, if present at all, is weak. It occurs in the central and southern wheatbelt from Wyalkatchem south then east in an arc to near Kulin and Pingaring. Occurs on slightly rising ground on a variety of well-drained soil types (see Nicolle & French, ibid.). (Formerly E. erythronema var. erythronema in part). 

E. armillata
The buds are strongly flanged around the middle and this flange is obvious in the fruiting stage. Buds and fruit are usually weakly and irregularly ribbed also. Flowers predominantly red; buds and branchlets always non-glaucous. It occurs only in the central-northern wheatbelt in an area bounded by Calingiri, Coorow, Canna, Wubin and Beacon, on level sites with gravelly soil. (Formerly known as E. erythronema var. marginata).

Eucalyptus erythronema: Greek erythro-, red and nemos, thread, referring to the usually red stamens.

subsp. inornata: from  the Latin inornatus meaning un-adorned, referring to the lack of wax on the branchlets, and also referring to the lower horticultural appeal of this subspecies (fide Nicolle & French (2012)).