Flowering time (month)
January to February
Ornamental or utility value
The eucalyptus (Eucalyptus gunnii), actually cider gum eucalyptus, is the only eucalyptus species of the myrtle family (Myrtaceae) that is regularly available from us. Only quite rarely, other types are offered in the trade, that however all show a clearly lower cold-tolerance. Like all genus members, the plant also known as the blue gum tree comes from Australia. There are whole eucalyptus forests in which koalas live that have specialized in eucalyptus leaves as food. This is remarkable from more than one point of view, as the leaves of eucalyptus are highly poisonous and low in calories due to their high concentration of essential oils. In our latitudes, Eucalyptus gunnii is cultivated as an exotic tree, mostly in tubs, but it can also be planted out in the garden.
While the eucalyptus grows at least ten meters high at its natural location, it remains relatively small here in the United States at 300 to 500 centimeters. Nevertheless, eucalyptus also shows itself to be extremely vigorous here: young plants grow between 30 and 50 centimeters in height every year. The evergreen plant grows in one or more stems, either as a tree or as a large shrub. With the help of regular cuts, the habitus becomes nicely bushy, but still remains slender and upright. Eucalyptus reaches an average growth width of 100 centimeters as a tub plant.
The leaves of the eucalyptus smell, one cannot say otherwise, like cough drops. They contain up to 3.5 percent eucalyptus oil, which has an expectorant and antibacterial effect on colds and is therefore an important component of various cough preparations and lozenges. Fresh eucalyptus leaves are bluish-green and round – the age leaves, on the other hand, are silvery-green, elongated oval and up to ten centimeters in size. Tip: For a healthy cold bath, simply remove some of the older leaves from your eucalyptus and put them in the bathtub. The hot water releases the essential oils perfectly.
The flowering time of Eucalyptus gunnii falls on the Australian summer, so it is in the winter months. From about December to February, small creamy white to slightly yellowish clusters of flowers appear on the plants. However, they do not form reliably only after several years and in our latitudes.
The capsule-fruits with the seeds of the blue-gum-tree are called also “gumnuts” (“rubber-nuts”) in Australia. They are round and green or reddish brown in colour, depending on their stage of ripeness.
From April – in colder regions better from the end of May – until October the eucalyptus can stand outside on the balcony or terrace. For hibernation, the potted plant must go into the house. Eucalyptus gunnii needs a full sunny location inside as well as outside. A lot of light is especially important when the plant is cultivated all year round in the winter garden or in the room. If there is a lack of light, the plant reacts immediately with leaf ejection. Only in mild regions is it advisable to plant your eucalyptus in a protected and fully sunny place in the garden. The scent has a deterrent effect on mosquitoes.
Eucalyptus usually gets along quite well with garden soils in this country, unless they are heavily compacted. The ideal substrate for the pot is sandy-loamy, fresh to moist, rather acidic (pH value between 5 and 6) and has a high nutrient and humus content. The planting place in the garden should be prepared accordingly.
Eucalyptus has a very high water requirement and must be watered abundantly, penetratingly and very often during its growing season (from spring to autumn). Only use water with a low lime content or rainwater: Eucalyptus gunnii does not tolerate high lime contents. Even in winter, the root ball should never dry out and must be kept constantly moist. It is then best to cast similarly often, but a little more sparingly. If there is a lack of water, the blue gum tree loses its leaves immediately and must be radically cut back as a saving measure.
Potted plants expect regular fertilisation during the growing season. So supply your eucalyptus with liquid flower fertilizer once or twice a week. In winter, fertilizers are applied only every two weeks and only when the plant is warm.
You only repot Eucalyptus gunnii after the old pot has been intensively rooted – this avoids unwanted growth spurts. For the same reason, make sure that the new vessel is only a few centimeters larger. The best time for repotting is in spring, in March, when the plant has just finished hibernating.
March is also a good time to cut the blue gum tree. Eucalyptus gunnii is very well tolerated to cuts and thanks regular cuts with a dense, bushy appearance and a compact growth. You can easily bring it to the desired size (not unimportant for pure houseplants or in the conservatory) or rejuvenate it. The plant then sprouts reliably and above all quickly.
Although Eucalyptus gunnii is hardy up to -15 degrees Celsius, it should be used as a tub plant indoors during the winter. The suitable wintering grounds are very bright and five to ten degrees Celsius cool. At dark locations the evergreen wood loses its leaves. Outdoor plants are particularly susceptible to frost cracks caused by the winter sun – you can prevent this by wrapping a reed mat or sacking around the trunk.
With a little luck you will also find varieties of Eucalyptus gunnii on the market. Especially beautiful are ‘Silver Drops’ and ‘Azura’, which have beautiful silver or blue-green leaves.
Eucalyptus is usually propagated by sowing. Original Australian seed is available in specialist shops or online. The optimum germination temperature is 20 degrees Celsius. You can also try your luck with half mature head cuttings, but it is very difficult to root them.
Diseases and pests
Most pests are kept away from Eucalyptus gunnii by the essential oils. A lack of water, however, can put the plant under such stress that it becomes susceptible to aphids or mealybugs. Plant diseases, on the other hand, almost never occur.
Your plant has mealy bugs? In an interview with our store editor Dieke van Dieken, herbalist René Wadas reveals how you can recognise an infestation and how you can combat the pest if necessary: Production: Folkert Siemens; Camera: Fabian Primsch; Editing: Dennis Fuhro; Photo: Flora Press/BIOSPHOTO/Alexandre Petzold
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I am Don Burke, one of the authors at My Garden Guide. I am a horticulturist that cultivates, grows, and cares for plants, ranging from shrubs and fruits to flowers. I do it in my own garden and in my nursery. I show you how to take care of your garden and how to perform garden landscaping in an easy way, step by step.I am originally from Sydney and I wrote in local magazines. Later on, I have decided, more than two decades ago, to create my own blog. My area of specialization is related to orchid care, succulent care, and the study of the substrate and the soil. Therefore, you will see many articles dedicated to these disciplines. I also provide advice about how to improve the landscape design of your garden.