Eucalyptus regnans

Cultivation Details

Eucalyptus regnans is native to the temperate climate of southeastern Australia, where it is found at elevations up to 900 metres. Rainfall occurs mainly in the winter, with a mean annual rainfall within the range 750 - 1,650mm. The mean maximum temperature of the hottest month is 23°c; mean minimum temperature of the coldest month is 0 - 2°c, and there are generally up to 80 frosts a year^[1]. When dormant, the plant can survive temperatures down to about -7°c, but young growth is more tender and can be severely damaged at -1°c^[2]. Requires a sunny position, succeeding in a wide range of well-drained soils of high fertility^[2]. Prefers a pH in the range 6 - 7, tolerating 5.5 - 7.5^[2]. The Eucalyptus regnans forest is a magnificent forest and is the tallest hardwood forest in the world^[1]. Annual wood production potential is 11 - 25 cubic metres per hectare^[2]. Whilst most Eucalyptus species, grown in small numbers outside their native range, can be an attractive and useful addition to the landscape, certain species (including this one) are more problematic. When grown in monocultures, especially outside their native range, they can become an environmental disaster. They are voracious, especially in their use of water; they are allelopathic, inhibiting the growth of the native flora; they reduce habitats for native fauna; and encourage the worst possible attitudes to land use and conservation^[3]. Plants are shallow-rooting and, especially in windy areas, should be planted out into their permanent positions when small to ensure that they do not suffer from wind-rock^[4]. They strongly resent root disturbance and should be container grown before planting out into their permanent position^[5]. Eucalyptus regnans is an important production forest species in New Zealand where it has been grown for several decades. Plantations have been successfully grown, utilized and re-established in the South Island. On pumice soils in high rainfall areas in the North Island, the tree must be carefully sited to avoid frost hollows, and preferably fertilized; if this is done it grows faster than Pinus radiata of high quality and produces at least 25 cubic metres per hectare per year. In South Africa, it has been grown successfully on the southern coastline close to very good plantations of Eucalyptus diversicolor, but there is not enough land to make significant industrial plantations of sawtimber and it is not a coppicing species. In Kenya, on the equator, but at around 3 000 metres elevation, a small plantation had a top height of 80 m in 30 years^[1]. Eucalyptus species have not adopted a deciduous habit and continue to grow until it is too cold for them to do so. This makes them more susceptible to damage from sudden cold snaps. If temperature fluctuations are more gradual, as in a woodland for example, the plants have the opportunity to stop growing and become dormant, thus making them more cold resistant. A deep mulch around the roots to prevent the soil from freezing also helps the trees to survive cold conditions^[3]. Many members of this genus are remarkably adaptable however, and there can be a dramatic increase in the hardiness of subsequent generations from the seed of survivors growing in temperate zones^[3].