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E. radiata- "Grey Peppermint" (Australia) I know little about this medium-sized tree, said to have a beautiful weeping form. It could be hardy to anywhere from 6 - 16 F.
E. regnans- "Australian Mountain Ash" PHOTO (southeastern Australia, including Tasmania) If this tree is well-known, it is because some confusion exists as to whether or not this is the world’s tallest tree. It seems the California Redwood (Sequoia sempervirens) is the tallest living tree, reaching a height of 365', but historically taller trees (including redwoods) than that have been measured. In 1898 a Douglas Fir (Pseudotsuga menziesii) found in a canyon in British Columbia was measured at 402' tall. As for the Australian Mountain Ash, the tallest one ever recorded measured 464' tall, but that was a long time ago and many people today do not consider that to be a reliable report. Another tree measured 435' to its broken top in 1872, and was said to have unquestionably been at least 80' taller than that before the top broke off, judging by the thickness of the trunk where it broke. Now they cannot find this tree anymore–some suggest that the top broke off again down lower, which is why they can’t find a 435' long log on the ground. Others do not accept this to be a reliable report either and consider the tallest one ever measured to be 373'. In any case, it is without question the world’s tallest nonconiferous tree. In cultivation it is a fast-growing tree with a straight trunk, and it has proven much more drought-tolerant than I was expecting it to (it grows naturally in relatively moist areas). It is one of the “half-barked” eucalypts, meaning that, in mature trees, the bark persists at the base of the trunk but is shed annually above about 20 - 40' up the tree (see also E. delegatensis). The leaves are bright green when young, becoming slightly more blue-grey in mature foliage but still somewhat greenish. It makes a magnificent specimen tree and is also valued for its timber where hardy. Natively it grows in areas subjected to considerable snowfall, but not so much severe cold or sudden drops in temperature--hardy to 11 - 16 F or so. Unlike most species, this one does not usually form a well-developed lignotuber and is unlikely to regrow if frozen to the ground.
E. risdonii- "Risdon Peppermint" (Tasmania) This species is rare in its native habitat, but well worth growing as an ornamental for its open-growing, weeping habit; smooth, pale bark; heart-shaped, silvery-blue juvenile leaves; and copious quantities of creamy-white flowers. Probably hardy to somewhere between 9 - 14 F.
E. robusta- "Swamp Mahogany" (coastal southeast Australia) A strong-growing, tough tree that does well in poor swampy or salty soil; also adaptable to a dry climate. The leaves are a very dark green, the bark is dark and rough, and pink flowers are produced in copious quantities. Hardy to 10 - 16 F.
E. rodwayi- "Swamp Peppermint" (Tasmania) This species has reddish-purple twigs and dark leaves and a dense crown that casts good shade. It is not exceptionally fast-growing and can reach about 60' sometimes. It is also renowned for its ability to grow in cold swampy soils and heavy clay. This is not the same species as E. aggregata though the two are often confused Very hardy, probably to about 2 - 7 F.
E. rubida- "Candle-bark Gum" PHOTO (southeastern Australia, including Tasmania) A large (to 150') fast-growing tree closely allied to E. dalrympleana with very attractive light blue-green leaves that can have kind of a pinkish, purplish or bronze tint. The bark, which peels in ribbony strips, is mostly white and sometimes partly cream or tan in places. Reportedly tolerates drought well for an alpine species. This species is widely distributed throughout the Australian uplands and can therefore vary greatly in hardiness, usually between 3 - 15 F.
E. salmonophila- "Salmon Gum" (Western Australia) Few species from Western Australia are likely to prove hardy; this one, in my opinion, is one if the best, and, if successful, most rewarding ones to try. The growth habit is extremely striking--a large tree shaped like an upside-down pyramid with billowy masses of foliage at the top, and brightly colored bark in every shade from grey to pink to orange to cream. Withstands drought. Could be hardy to as low as 8 F; fast-draining soil helps it achieve maximum hardiness.
E. stellulata- "Black Sallee" PHOTO (eastern Victoria, eastern New South Wales) This species has a widely spreading thick crown and makes an ideal shade tree. It can grow to about 60' tall and has interesting olive green and white peeling bark. Seems fairly tolerant of poor wet soils and partial shade. Tiny fruit pods preceded by attractive star-shaped flowers are intriguing. Very hardy, withstanding 3 - 11 F. Another relatively well-known hardy eucalypt, and often categorized as one of the "snow gums."
E. stricklandii- "Strickland's Gum" (Australia) This fast-growing medium tree (to 30 - 45') is likely to be one of the hardiest species that has showy flowers. They are bright yellow and appear in the summer. I would think it hardy to near 10 - 14 F. Shelter is a must in zone 8.
E. sturgissiana- "Ettrema Mallee" (Australia) A small mallee (to 8') with beautiful blue-grey leaves. Hardy probably to 11 - 17 F.
E. subcrenulata- "Alpine Yellow Gum" (Tasmania) Closely allied to E. johnstonii, but not as tall (to 90') and with darker green leaves that have slightly scalloped edges. Also produces valuable wood, but the bark has yellow and green patchessimilar to those of E. johnstonii. The juvenile leaves are round and stem-clasping like those of many other species, but they are a deep green rather than blue. Said to be very beautiful, and good at retaining its foliage to ground level--it could make a good screen. Hardy to 1 - 7 F; will grow in exposed sites but not achieve more than 25 - 35' in height there.
E. tenuiramis- "Silver Peppermint" (Tasmania, perhaps mainland Australia) A "medium tree with slender pendulous branches and attractive blue leaves"--possibly hardy to 7 - 14 F.
E. urnigera- "Urn Gum" (southeast Tasmania) so named for its funky urn-shaped seed pods. It has pale-blue juvenile leaves which are variable in size, narrow blue adult leaves, and blotchy bark. It is reliably symmetrical in an open sheltered situation, and becomes gnarled and picturesque in exposed areas. Very fast growing, its ultimate height quite variable–anywhere from 55 - 130'. Hardy to 3 - 11 F.
E. vernicosa- "Varnished Gum" (Tasmania) A "small or prostrate branching shrub," this species is slow growing, for areas where space is a limitation. Little shiny leaves ("varnished") are attractive up close. Extremely hardy; I would guess to around 0 F--perhaps the hardiest of the Tasmanian species, but I don't know how well it will adapt to warm-summer cliamtes.
E. viminalis- "Manna Gum" (Australia, including Tasmania) PHOTO This species makes a large tree (to 120', sometimes more) that has peeling white bark with tan and cream-colored patches. It is incredibly fast growing--up to 10' per year, even in a cool-summer climate, and somewhat messy. Leaves are described as "narrow and soft" often with purple stems, bark shreds and is rather messy at the base; the trunk often has pink or yellowish patches but is mostly cream to white. Flowers throughout late winter and spring. Hardy to 4 - 14 F (New Zealand provenances are hardiest, but most in cultivation are on the less hardy side) and recovers from freezes well. Young trees 2 - 5 years of age are particularly beautiful.
E. youmanii- "Youman's Stringybark" (Australia) This tree is fairly large and "tolerant of frosts and snow." Since it shares the same native region with E. nicholii and E. nova-anglica I am guessing it is hardy to 5 - 11 F.
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