NZ Myrtaceae Key - Online edition

Eucalyptus cordata Labill.


Common Names

heart-leaved silver gum

Origin

Australia: south-eastern Tasmania.

Cultivation

In New Zealand occasionally cultivated.

Distribution

A few scattered records from mainly urban areas of the North and South Islands of New Zealand.

Distinguishing Features

  • Small tree with smooth bark, variously coloured, that can be greenish yellow, white, brown, green, grey or purple, and waxy grey-white branchlets.
  • Mature and flowering with persistent juvenile foliage.
  • Crown bearing waxy grey-white juvenile leaves or a mixture of juvenile and intermediate leaves; occasionally adult leaves at top of crown.
  • Crown leaves (including juvenile, intermediate and adult leaves), opposite or alternate, blade broadly rounded to lanceolate, to 130 mm long and 80 mm wide, tapered to base varying to stem-clasping; margins smooth or scalloped; dull, usually waxy grey-white, or blue-green or grey-green, sometimes green.
  • Flowers in clusters of three, in leaf axils, stalkless or rarely short-stalked; mature buds club-shaped to oblong, to 13 mm long and 9 mm wide, green or waxy grey-white, cap rounded to flattened to narrowly pointed; flowers white.
  • Fruit are woody capsules, stalkless or rarely short-stalked, cup-shaped, cylindrical or hemispherical, to 13 mm long and 15 mm wide, usually waxy grey-white, disc descending inside the rim, valves 3 or 4, near rim level.

Habit

Single-stemmed shrub to 3 m or tree to 21 m tall, mature and flowering in the juvenile phase.

Bark and Stem/Trunk

Bark smooth, greenish yellow, white, brown, green, grey or purple; branchlets waxy grey-white; ribbons absent. Hairs and adventitious roots absent. Young stems may be square or rounded in cross-section, waxy grey-white, warty.

Leaves

Adult leaves, usually only found at the tops of taller trees, sub-opposite to alternate, stalked, lanceolate, to 130 mm long, to 38 mm wide, dull, blue-green or grey-green to waxy grey-white, same colour on upper and lower surfaces.

Juvenile leaves opposite for many pairs, stalkless, base stem-clasping, overlapping the leaf on the opposite side of the stem, rounded to heart-shaped, to 100 mm long, to 80 mm wide, waxy grey-white with scalloped edge.

Crown may be of juvenile leaves only or mixture of juvenile with leaves intermediate between juvenile and adult. Crown leaves (including juvenile, intermediate and adult leaves) opposite or alternate, blade broadly ovate to round to heart-shaped to lanceolate, 50–130 mm long, 25–80 mm wide, base tapering to stalk to lobed to stem-clasping; margin smooth, sometimes scalloped, same colour above and below or slightly different, dull, usually waxy grey-white, or blue-green or grey-green, sometimes green; side-veins at an angle greater than 45° to midrib, vein reticulation moderate to dense, intramarginal vein well removed from margin, hairs absent; leaf stalk 0–15 mm long.

Flowers

Flowers in clusters of three, in leaf axils, stalkless or rarely stalked to 10 mm long. Mature buds club-shaped to oblong, 9–13 mm long, 7–9 mm wide, green or waxy grey-white. Mature buds are free, stalkless or shortly stalked, bud cap rounded to flattened to narrowly pointed, flowers (stamens) white; in mature open flowers, petals and sepals absent. Main flowering period: autumn to winter.

Fruit

Capsules woody, stalkless or rarely short-stalked to 10 mm, cup-shaped, cylindrical or hemispherical, 6–13 mm long, 8–15 mm wide, sometimes with slight longitudinal angles down the outside, usually waxy grey-white, disc descending inside the rim, valves 3 or 4, near rim level.

Similar Species

Eucalyptus gunnii, E. cordata and E. perriniana are in a group of eucalypts with orbicular to heart-shaped juvenile leaves that are opposite for many nodes, have a grey-green to blue-green tree crown, and buds in threes. These three species all have smooth bark. Capsules are usually waxy grey-white, cup-shaped or cylindrical.

  • The bark of E. cordata is mottled, branchlets usually waxy grey-white. The crown of E. cordata has waxy grey-white, stalkless, stem-clasping, juvenile leaves or a mixture of juvenile and intermediate leaves, and occasionally adult leaves at top of the crown. Leaf margins may be scalloped.
  • Eucalyptus gunnii sometimes has up to one metre of rough bark at the base, the smooth bark is usually mottled, and branchlets are often conspicuously waxy grey-white. Juvenile leaves are broadly round to heart-shaped, grey-green or waxy grey-white, the margin smooth or scalloped. The crown often has conspicuously waxy grey-white new growth amongst grey-green to blue-green, more lanceolate adult foliage. Capsules are cylindrical to barrel-shaped, often slightly contracted below rim.
  • Eucalyptus perriniana has smooth bark that is copper-coloured when new, weathering to greenish or white, with a small amount of rough bark remaining at the base of large trees. Tree crowns retain many opposite, stalkless, smooth-edged juvenile leaves that are joined across the stem to the leaf on the other side; stalked, lanceolate intermediate and adult leaves are not always formed.
Eucalyptus cinerea and E. cordata foliage and buds look very similar, both with mainly grey-green to waxy grey-white foliage and buds in clusters of three in leaf axils. In both species the crown of mature trees is composed of juvenile and intermediate leaves. Leaf margins of E. cinerea are smooth, whereas those of E. cordata are usually scalloped. Woody capsules of E. cordata are cup-shaped, cylindrical or hemispherical, compared with funnel-shaped to bell-shaped capsules of E. cinerea. Branchlets of E. cordata may be square and warty, but young stems of E. cinerea are round. The most distinctive difference is that E. cordata bark is smooth, sometimes with curling or flaking patches, but E. cinerea bark is rough with longitudinal furrows.

Notes

Two subspecies, formalised in 2008, are defined in Australia. Eucalyptus cordata subsp. cordata, the eastern form, has branchlets rounded in cross-section both in reproductive plants and coppice growth, and is always a large shrub, never a tree. Eucalyptus cordata subsp. quadrangulosa, restricted to the subcoastal ranges of south-eastern Tasmania, has branchlets squared in cross-section both in reproductive plants and coppice growth, and can form much larger shrubs and trees to 25 m tall. In New Zealand herbaria, there are no specimens determined to subspecies. It is probable that the more common subspecies is present in New Zealand, but subspecies status has not been determined.

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.

Creative Commons Attribution 4.0 International Licence (CC BY 4.0).