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Eucalyptus regnans
Also called Stringy gum, Swamp gum, Tasmanian oak, Victorian ash, Australian Oak, Giant Ash, White Mountain Ash
Eucalyptus regnans is the tallest flowering plant, a giant evergreen forest tree from Victoria and Tasmania, too large for most gardens. It needs cool, wet, fertile, well-drained conditions and is rarely grown outside its native range or plantations.
Eucalyptus regnans, known variously as mountain ash (in Victoria), giant ash or swamp gum (in Tasmania), or stringy gum, is a species of very tall forest tree that is native to the Australian states of Tasmania and Victoria. It is a straight-trunked tree with smooth grey bark, but with a stocking of rough brown bark at the base, glossy green, lance-shaped to curved adult leaves, flower buds in groups of between nine and fifteen, white flowers, and cup-shaped or conical fruit. It is the tallest of all flowering plants; the tallest measured living specimen, named Centurion, stands 100 metres (328 feet) tall in Tasmania.
It often grows in pure stands in tall wet forest, sometimes with rainforest understorey, and in temperate, high rainfall areas with deep loam soils. A large number of the trees have been logged, including some of the tallest known.
Eucalyptus regnans is too large for the majority of gardens, but may be suitable for parks. Propagation is from seed, with the best germination rates being obtained by refrigerating for three weeks before sowing. Seed may be stored for several years if refrigerated and kept dry. Seedlings are grown in containers but are more prone to damping off than other eucalypts; they are highly susceptible to Phytophthora cinnamomi and P. nicotianae. Young plants are generally planted out once they are 8 or 9 months old. These are at risk of being eaten by grazing rabbits, wallabies and possums, which can destroy young plantations in severe cases.
American horticulturist and entrepreneur Ellwood Cooper noted its rapid growth but demanding soil requirements in his 1876 work Forest Culture and Eucalyptus Trees. Eucalyptus regnans requires fertile soil with good drainage and annual rainfall of 1,000 millimetres (39 in) spread over the year, and has poor tolerance to temperatures below −7 °C (19 °F) or drought.
Eucalyptus regnans occurs across a 700 km by 500 km region in the southern Australian states of Victoria and Tasmania. The species grows mostly in cool, mountainous areas that receive rainfall over 1,000 millimetres (39 in) per year. E. regnans reaches its highest elevations of about 1,100 metres (3,600 ft) ASL on the Errinundra Plateau in north-eastern Victoria, and its lowest elevations near sea-level in some southern parts of its Tasmanian distribution.
Eucalyptus regnans is valued for its timber, and has been harvested in very large quantities. Aside from being logged in its natural range, it is grown in plantations in New Zealand and Chile, and to a limited extent, in South Africa and Zimbabwe. Primary uses are sawlogging and woodchipping. It was a major source of newsprint in the 20th century. Much of the present woodchip harvest is exported to Japan. While the area of natural stands with large old trees is rapidly decreasing, substantial areas of regrowth exist and it is increasingly grown in plantations, the long, straight, fast growing trunks being much more commercially valuable than the old growth timber.
White eucalyptus · New England Stringybark · River redgum · Coowarra Box · Coolabah · Narrowleaf red ironbark · White gum · Indonesian gum · River peppermint gum · Tasmanian bluegum · Cider gum · Araluen Gum
Text excerpted from the Wikipedia article Eucalyptus regnans by its contributors, under CC BY-SA 4.0; the excerpts and the care summary drawn from them are shared under the same licence.
The care summary was written by AI (Claude, Anthropic) from the sources on this page, with general growing knowledge where they are silent. Check before relying on it.
Life form, climate and native range: World Checklist of Vascular Plants, Royal Botanic Gardens, Kew (CC BY 3.0), reformatted; see Plants of the World Online.
