Eucalyptus robusta Sm.

swamp mahogany, swamp messmate

Australia: coastal New South Wales to south-eastern Queensland.

In New Zealand predominantly cultivated for timber or amenity; very occasionally naturalised from nearby specimens.

Mainly in northern coastal and lowland areas in the North Island of New Zealand.

• Tree with thick, fibrous, spongy, reddish-brown to grey-brown bark with deep longitudinal furrows, extending to the small branches.
• Mature leaves that are glossy, darker green on the upper side, paler beneath, strongly feather-veined.
• Long-stalked, spindle- or pear-shaped flower buds to 20 mm long and 9 mm wide, in clusters of 9–15.
• Fruit that are woody capsules, long-stalked, cylindrical to 18 mm long and 11 mm wide, with disc descending inside rim of capsule, and the three or four valve tips joined across the mouth of the capsule.

Tree to 30 m tall.

Bark of main trunk thick, fibrous, spongy, reddish-brown to grey-brown, in elongated slabs with furrows between, extending to the small branches; ribbons absent. Hairs and adventitious roots absent. Young stems square in cross-section, sometimes winged.

Mature leaves alternate, stalked, broadly lanceolate to ovate, feather-veined, tip pointed, base tapering to leaf stalk, glossy, dark green above and paler below, hairs absent, 85–170 mm long, 25–70 mm wide. Vein reticulation moderate to dense, main side-veins at a relatively wide angle to the midrib, intramarginal veins present just inside margin; oil glands usually inconspicuous; leaf stalk 15–30 mm long.

Juvenile leaves always stalked, opposite for 5 to 7 pairs then alternate, ovate to broadly lanceolate, 60–190 mm long, 25–80 mm wide, bases round to tapering, dark green above and paler below, dull, green.

Flowers in clusters of 9–15, in leaf axils, stalk of cluster broadly flattened, 15–30 mm long. Flower buds with prominent stalks to 9 mm or more long; mature buds free, spindle- to pear-shaped (16–20 mm long, 6–9 mm wide), yellow or creamy, bud cap conical or narrowly pointed, flowers (stamens) white; in mature open flowers, petals and sepals absent. Main flowering period: winter and spring with some flowering from late autumn.

Capsules woody, stalked (stalks 5–12 mm long), cylindrical, 10–16(–18) mm long, 6–11 mm wide, disc descending inside rim, valves three or four, valve tips usually joined across the mouth of the capsule when fruit has dehisced, below or near rim level, rarely slightly projecting above the rim.

• Eucalyptus botryoides, southern mahogany or bangalay, has generally similar leaves, buds and capsules, and thick bark over the whole trunk to the large branches. However, its buds are shorter with conical or hemispherical caps, and usually stalkless or nearly so. The capsules are usually cylindrical to barrel-shaped, with valve tips ± level with capsule rim but not joined across the mouth of the capsule.
• Eucalyptus saligna, Sydney blue gum, has generally similar leaves, buds and capsules, although its buds tend to be smaller and slightly pear-shaped, and the capsules, are smaller than those of E. robusta, with valve tips erect above the rim of the capsule. The greatest difference is that E. saligna has smooth grey-green or bluish-green bark on the main trunk, with only a basal stocking of rough bark.

Eucalyptus is a genus of nearly 800 species, most of which are endemic to Australia, with a few species extending to parts of Malesia and as far north as the Philippines.

• EUCLID
• Flora of Australia
• Flora of New Zealand Online
• GBIF
• iNaturalist NZ
• NZPCN
• PlantNET: New South Wales Flora Online
• Plants of South Eastern New South Wales