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Eucalyptus

Ulrike Hanninger Ulrike HanningerFolkert Siemens Folkert Siemens

The Eucalyptus genus has many facets which mean it can be planted at a variety of latitudes. Let us introduce you to the species and give you some practical tips.

Origin

If you have ever eaten a cough mint, you’ll be able to recognize the scent of species from the botanical Eucalyptus genus without any doubt: The essential oils can be easily smelt by rubbing the leaves. There are over 600 Eucalyptus species in total, and they are all native to moderate to tropical Australia or Indonesia. In Australia, they are the dominating tree species making up 70 per cent of all forests. The fast growing myrtles (Myrtaceae) all develop as stately trees or large shrubs. The Mountain Ash Eucalyptus (Eucalyptus regnans) is even considered the tallest deciduous tree in the world - in Tasmania, one specimen was discovered with a growth height of 164 feet and a 66 feet circumference.

Appearance and Growth

Eucalyptus usually grows as a tree, and more rarely a shrub, and forms upright crowns. Its bark is light-gray to silver-gray, depending on the species, and often develops leaves in elongated plates, which gives the trunk an interesting pattern. The generally elongated, single leaves are opposite one another in young plants, in older plants they often alternate. In addition, some species the wood changes its shape (heterophyllie) with increased age. The colors vary from green to blue-green and gray. The individual flowers of the Eucalyptus generally stand on umbellar inflorescences, similarly to Callistemon, do not have conspicuous bracts but do have intensive colored white, yellow or red stamens, depending on the species. The capsule fruits are also called "gumnuts" in Australia.

Eucalyptus flowers and fruit

Eucalyptus flowers and fruit are rarely seen

Location and Soil

As in its natural location, the eucalyptus needs a location in full sunlight - ideally all year round. Specimens in the garden must also be protected against the wind. Eucalyptus have a few soil requirements: Outdoors, soil should be permeable, sandy-loamy, fresh to moist and more acidic, as well as nutrient-rich. Indoors, a drainage layer of expanding clay, gravel or similar is advisable, while the soil should be more meagre and also acidic. Increased lime content does not suit the Eucalyptus indoors or outdoors.

Planting

Eucalyptus is generally commercially available as a small pot plant. The best time to plant is in the early summer. Larger specimens should be supported with a rod and tied to this if necessary.

Eucalyptus in a tub

With a suitable substrate, the Eucalyptus develops wonderfully, even in a tub

Care Tips

Eucalyptus plants are extremely thirsty and need plenty of water during the vegetation period. Only use rain water, if possible, as almost all species and varieties react sensitively to high lime content. It is not generally necessary to fertilize, as the plants naturally grow in more low nutrient soils. However, indoors you can support the Eucalyptus by fertilizing it weekly with minimal dosing. Eucalyptus species should only be re-potted if the pot is intensively rooted through, so as not to provoke an unnecessary growth spurt. The best time is in the spring, after the winter break. Take care not to damage the sensitive roots: You should neither cut nor break these.

Pruning

Long shoots must be regularly trimmed to maintain compact growth of this tree-like plant in a pot. If the shoots have dropped their leaves due to a lack of water, only a rejuvenation cut can help. However, in general, Eucalyptus tolerates pruning well.

Eucalyptus tree

In suitable location conditions and with sufficient space, Eucalyptus grows into a stately tree. If you want to cultivate it in a tub, you will have to prune it

Overwintering

Eucalyptus should be overwintered somewhere cool and light, if possible. In a dark winter residence, the evergreen trees will often drop their leaves. Outdoor plants are particularly susceptible to frost splitting from the winter sun - this can be prevented by wrapping reed mats or burlap around the trunk.

Utilization

As a container plant, Eucalyptus species are suitable for very warm, full-sun terraces and roof gardens where they can spend the summer months outdoors. In a conservatory or greenhouse they ensure fresh greenery and a touch of the exotic all year round.

In forestry, these fast growing trees, which form very straight trunks, are used in particular as pulp suppliers. The wood of older specimens of certain species is also suitable as timber. As the tree is also used in forestry outside of its natural home, some Eucalyptus species have also spread extensively across other continents in the meantime, for example as neophytes. The koalas which live in Australia have a diet which specializes in Eucalyptus leaves, although the foliage hardly contains any calories and is also extremely poisonous due to the essential oils.

Eucalyptus oil

Eucalyptus oil has a health-promoting effect and helps in particular with colds and coughs

Eucalyptus as a healing plant

Eucalyptus leaves contain up to 3.5 per cent eucalyptus oil - this has an expectorant and anti-bacterial effect on cold illnesses and is an important component of various cough preparations. Cough sweets or cold-relief bath additives with eucalyptus alleviate throat irritation and complaints in the throat area in general. Eucalyptus is also used in the perfume and cosmetics industry and is contained in toothpaste, skin tinctures, shower gels and medicinal soap, among other things.

Important Species and Varieties

In Central Europe, there are only a handful of species of Eucalyptus which are cultivated as container plants. Of these, only the cider gum tree (Eucalyptus gunnii) has a high enough cold tolerance (down to 5 degrees Fahrenheit) that it can survive in mild places as an outdoor plant. In the English Kew Gardens in London, for example, huge specimens of this type of tree can be admired. However, in the average garden or house, a growth height of 118 to 197 inches can be expected. This species requires lots light in order to thrive, otherwise it drops its leaves.

Unlike most other species, Eucalyptus citriodora, the lemon-scented gum, does not exude a cough sweet aroma, rather an intensive citrus fragrance. It also develops well indoors, but must be regularly pruned due to its strong growth. The red-flowering gum (Eucalyptus ficifolia) is very popular due to its red, brush-like inflorescences and is considered one of the most beautiful species. Its flowering period begins towards the end of August.

The Rainbow Eucalyptus (Eucalyptus deglupta) holds a special position within the genus: Not only is its trunk rainbow colored, it is also the only species which grows far away from Australia and is even native in the northern hemisphere. However, in the northern hemisphere it can only be cultivated with some effort in heated rooms with high humidity, such as in a conservatory or a greenhouse. But it is certainly an eye-catcher.

Propagation

Members of this genus are only propagated through seed sowing. Propagation through cuttings is possible, but only rarely met with success.

Diseases and Pests

The plants are hardly susceptible to diseases, but do suffer occasionally from aphids. Container plants tend to develop gray mold in the winter.

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