Tree of the Week: Red ironbark

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Good morning, and happy November. May you be as successful in November as Pete Carroll has been. This will be my final post of Pieter Severynen’s ‘Tree of the Week’ -- the longest running feature on L.A. Land, and one that I hope will continue to appear on Saturday mornings. Thank you, Pieter, you are a gentleman and a scholar.

Red Ironbark -- Eucalyptus sideroxylon ‘Rosea’

In 1770 Joseph Banks and Daniel Solander arrived at Botany Bay on Australia’s coast with Captain James Cook. They returned to England with the first eucalyptus seeds from Down Under. More species became known and in 1878 at age 78 George Bentham published the still current and unsurpassed Flora Australensis describing Australia’s native trees. He called the wood of the ironbark heavy, red in color and hard as iron. Ironbark trees are so named because with age the bark becomes perfused with kino (a thick reddish sap exuded by eucalyptus trees that oxidizes to black), which makes the bark tough and non-shedding.

‘Rosea’ is the red-flowering form of the Ironbark, a rather attractive and graceful Australian eucalypt. This moderately fast-growing evergreen tree is quite variable: 30 to 90 feet tall, 30 to 60 feet wide, upright or weeping, open or dense. The tree becomes more spreading with age. Deeply furrowed rusty red bark covers the trunk. Slender, 6-inch-long, curved, gray-green leaves on the pendant branches turn bronze in winter. The fall-through-winter-blooming pink or red flowers are typical for eucalyptus, i.e. flower parts are bunched together in a cap whose cover falls off come blooming time, exposing the colorful fluffy stamens. Hence the name ‘eu-calyptus’ for ‘well-covered’. Woody seed capsules are flat-topped. The ironbark tolerates smog, considerable drought and various soils. It has a tendency to bifurcate, or form structurally weak double trunks. This is best corrected at an early age. The ironbark exhibits fewer problems than some other large eucalypts, but attacks by insects such as psyllids and longhorn beetles, the tree’s competition with neighboring plants, and its potential invasiveness make it advisable to use it only in small quantities under controlled conditions.

Eucalypts originated soon after Australia separated from the Gondwanaland continent. As the climate gradually became drier, a more open forest type replaced the rainforest. Aborigines contributed to a more frequent fire regime and the fire-adapted eucalypts, by now numbering over 600 species, came to dominate the Australian forests. The ironbark is native to East Australia (Queensland and New South Wales).

Thanks, Pieter, it has been a pleasure working with you.

--Peter Viles

Photo Credit: Pieter Severynen.