Eucalyptus is a huge genus of around 800 species of fast-growing, evergreen trees and shrubs. They are known for their attractive, often peeling bark, in shades of white, cream, grey-green and even pink or red. Their usually glaucous foliage is also attractive, with juvenile foliage often taking one form and adult foliage another.
Most species are native to Australia but they are also found in New Guinea, the Philippines and Java. UK growers need to be aware that many species are not hardy enough for our climate, especially in the past five years when winters have been quite tough. But there are quite a few that are hardy or will cope if planted in a warm, sheltered garden.
The toughest species is probably Eucalyptus dalrympleana Award of Garden Merit (AGM), the mountain gum. Being from high altitudes, it can cope with sub-zero temperatures and is also said to handle dry summers, wet winters and clay, lime or acid soil. Another hardy type is E. coccifera, the Tasmanian snow gum. This is a neat, upright little tree with olive-green leaves and flaking white-pinkish bark.
The most commonly known gum in the UK is E. gunnii AGM. It has circular, silvery-blue juvenile leaves that make it popular with florists. It is one of the hardiest and has flaking bark in shades of grey, cream, green and brown. Another that produces attractive juvenile foliage is the spinning gum. The leaves are fused around the stem until they dry out, then they pull away from the stem and spin in the wind. Often the varieties with attractive young foliage are coppiced or pollarded to continually produce new foliage. This can also have the benefit of restricting growth - left alone, many eucalyptus will become tall trees.
It no longer stands, but the tallest tree ever recorded was a specimen of E. regnans in south-east Australia. It was estimated to have been more than 150m tall in 1872. To give that gargantuan size some perspective, consider that the tallest tree today is the coastal redwood, known as Hyperion, which is 115.72m high.
It is recommended when planting eucalyptus to start with a small specimen of up to 1m tall. If planted too large, the top growth tends to get away before the roots are properly established, leading to instability and the likelihood of damage in high winds. It is no good to counter this with a stake either, because it leads to a weak plant whose trunk will not harden enough to stand up for itself when the stake is removed.
The right soil for the right species is also a quite a major consideration because the eucalyptus species come from many varied habitats. Most prefer neutral to acid soils but some, such as E. dalrympleana AGM, thrive in very alkaline soils. The snow gums, including E. pauciflora, and many of the species with "ash" in their common name, such as the kybean mallee ash (E. kybeanensis), prefer drier soils. At the other end of the spectrum, the swamp gums (E. aggregata and E. rodwayi) thrive in wet, claggy ground.
So do not be afraid of using eucalyptus but choose the right species for your garden. Give large trees plenty of space and plant them away from buildings. Coppice or pollard the species with attractive juvenile growth. Grow them in a container if you are really cautious - they make a great patio plant.
What the specialists say:
- Hilary Collins, owner, Grafton Nursery, Worcester
"We specialize in eucalyptus and think they are amazing. They provide great structure for the winter garden with evergreen foliage and beautiful bark. There are 800-plus species, with each having evolved to cope with specific microclimates in different habitats.
"There are so many species to choose from. E. gunnii is still recognized as being incredibly hardy, along with E. pauciflora subsp. niphophila. The latter is a much better choice, being manageable for your average medium-to-large garden, and has the most beautiful bark.
E. perriniana has wacky juvenile foliage much loved by floral artists.
"We recommend that you plant a small tree - it will establish far quicker and won't require staking. If you do plant a larger specimen, don't stake it - it will fall over at a later date because the trunk will not lignify correctly. Choose the right species for your garden and think about how you will manage it. If you are going to let it grow into a full-sized tree it will need to be planted well away from buildings."
- Harriet Harker, nursery manager, Kings Barn Trees, West Sussex
"Eucalyptus are an overlooked genus. When you think of evergreen trees your mind automatically turns to spruces or firs, but in eucalyptus you have a flowering, broad-leafed evergreen with many other exquisite qualities. They are suitable for a wide range of uses from ornamental specimens to screening and windbreaks. It can also be grown for biomass or in a pot on your patio.
"They are highly ornamental trees with ornate peeling bark, coloured from white-grey to brown, pink and red, glaucous olive-green and blue leaves giving off a unique scent and masses of delicate white flowers in summer. Of the varieties that will grow in the UK, you can choose one that can tolerate almost any site.
"Their roots are vigorous and thirsty, so avoid planting near walls or buildings. Also, not all reportedly hardy varieties are completely hardy so double check before planting out in the middle of a field. A pest to watch out for is the blue gum psyllid. We had to spray infested trees with a mild soft-soap solution. Ladybirds and lacewings feed on them so if you encounter this pest encouraging their predators is a good idea."
- Andrew Fisher Tomlin, director, Fisher Tomlin & Bowyer, Surrey
"Eucalyptus can work if you have a big enough garden. A multi-stemmed tree in the middle of a large lawn, attached to a sizeable property, can look fantastic. I have also planted them in cutting gardens for clients. Then they have kept them as a shrub and used the juvenile foliage for floristry purposes.
"We planted a eucalyptus grove of lemon-scented gums in our recent show garden 'September Sky' at the Australian Garden Show that used other Australian natives. The issue with eucalyptus over here in the UK though is that they are seen as bit of a thug, can be difficult to source from nurseries and are not always fully hardy. We are perhaps more likely to be asked to take them out by a client rather than put them in."
Species and varieties
- E. coccifera is a neat, evergreen tree with mottled white and grey bark. Its foliage is peppermint scented - heart-shaped when juvenile but lance-shaped when mature. In summer, creamy-white flowers are borne. Fully hardy down to -15 degsC and wind-tolerant. Height: 18m. Spread: 8m.
- E. archeri, or the alpine cider gum, is a large hardy evergreen tree that develops attractive, smooth, white/grey bark that flakes and peels to show pink, greys, white and brown in a mosaic pattern. It is like a smaller version of E. gunnii with young leaves that are rounded and blue-green but said to respond better to pruning and coppicing. If not pruned for juvenile foliage, it will become a tall stately tree with long, weeping, glaucous foliage. Height: 16-20m. Spread: 8m.
- E. dalrympleana AGM (H4) is a tough, tall, fast-growing species featuring smooth, yellow, white to cream bark with grey, pink, brown and green patches. The leaves are oval, green or grey-green when young, but become long, thin and green. Height: 40m.
- E. glaucescens is a broadly conical tree or shrub with smooth white bark, rounded blue-white juvenile leaves and slender lance-shaped, blue-green adult leaves. Umbels of white flowers bloom in autumn. Height: 12m. Spread: 8m.
- E. gunnii AGM (H5) is one of the best-known species in the UK. Its juvenile, rounded, silvery-blue foliage is used by florists and it is one of the hardier types. It has lovely flaking bark in shades of grey, cream, green and brown and its adult foliage is glaucous, long and sickle-shaped. Height: 25m. Spread: 10m.
- E. nicholii is an elegant tree with a light, open crown and weeping habit. Leaves are narrow and lance-shaped, like those of a feathery willow. Can be grown as a specimen tree in a sheltered garden, but also in a pot for patio or conservatory. Responds well to pruning. Height: 12-15m.
- E. parviflora is a medium-sized, evergreen tree with peeling grey bark and narrow, drooping, blue-green leaves. Height: 10-15m.
- E. pauciflora subsp. niphophila AGM (H5) is a small, spreading tree with narrow, elliptic, grey-green leaves. Its young shoots have red stems with a white bloom. The tree's bark flakes attractively into cream, grey and green patches. Hardy down to -15 degsC. Height: 8m. Spread: 4m.
- E. perriniana is also highly popular with florists. Its juvenile foliage is fused around the stem until they dry out, allowing them to spin around the stem. This feature gives this eucalyptus the common name of spinning gum. Adult leaves are long, drooping, sickle-shaped and blue-grey in colour. It has smooth bark, which is white, green to pale copper, shedding in ribbons. It is a hardy species that copes with exposed sites. Responds well to hard pruning. Height: 15-20m.
Thank you to Floramedia, which supplied the images for this article from its photo library