When you think of koalas, you automatically connect eucalyptus trees to them. Did you know that they also thrive with us?
At first glance, you may not be thinking of a plant, but an aromatic candy when you call it eucalyptus. This is forgiven you. At the same time, it is also reason enough to take a closer look at the eucalyptus trees. These belong to the myrtle family, are also called blue rubber trees and are unexpectedly rich in species. More than 600 different species have already been described. Below is the giant eucalyptus, a true giant. The deciduous tree with the highest stature reaches almost 100 meters. For the amateur gardener, this crop is understandably less of interest. But there are also numerous species that feel good in the garden and on the terrace and like to spend the summer there. Eucalyptus also cuts a fine figure as a houseplant. The exotic plant proves to be quite easy to care for and robust. With the following tips and advice, you will surely enjoy your blue rubber tree for a long time.
The appearance of the eucalyptus
Due to the extraordinarily large diversity of species, there are also certain visual differences in the appearance of eucalyptus. As they age, the blue gum trees change the appearance of their bark. With new layers of bark, the trunk size of the trees is expanded annually. In some species the outer layer then peels off, in others it remains on the trunk. This gives the tribes a different appearance. There are also differences in the leaves. The leaves are usually opposite when they have sprouted. The adult leaves are usually heart to egg-shaped.
Origin and distribution
The original home of the eucalyptus trees is in Australia and Tasmania. The natural range of the plant genus also lies in the east of Indonesia. In Australia alone, three quarters of all tree species consist of eucalyptus plants. Numerous types of blue gum trees have become indigenous to the subtropics worldwide.
The eucalyptus was first scientifically described at the end of the 18th century by Charles Louis L'Héritiert de Brutelle, a French botanist who was based in London at the time. The plant name comes from ancient Greek and alludes to the closed calyxes with the words "beautiful" and "hidden".
The use of eucalyptus
Eucalyptus leaves serve as the Koala's favorite dish. Furthermore, the plant is used for the extraction of essential oils and also for wood extraction. Essential oil can be obtained from around 50 types of eucalyptus alone. Eucalyptus oil was already used for medical purposes around 1850. The plant's blood circulation and anticonvulsant effects were exploited. Areas of application for eucalyptus oil are:
- to cough
- bladder diseases
The leaves of the eucalyptus contain toxins. Eucalyptus oil should therefore not be taken in large quantities and is even taboo for people with high blood pressure, liver problems or diseases of the digestive tract.
When does the eucalyptus bloom?
The white flowers of the eucalyptus appear between September and December. The dold inflorescences are densely populated with flowers. The flowers are fourfold hermaphrodite. The buds are surrounded by a capsule called an “operculum”. When the flower opens and the stamens widen, the capsule comes off. The fruit clusters are often reminiscent of cones.
Overview of different types of eucalyptus
❍ Snow eucalyptus:
The snow eucalyptus comes from Australia and grows there in regions up to 1,800 meters. The robust species has a rather low growth height of a maximum of ten meters.
❍ Silver dollar eucalyptus:
The silver dollar eucalyptus only grows in Tasmania. The plants grow there as a tree or as a shrub. The growth height is between ten and twenty meters.
❍ Jarrah eucalyptus:
Jarrah eucalyptus grows in western Australia. The wood is not affected by termites and is valued in the manufacture of furniture and musical instruments. The trees can get very old. A specimen occurring in Armadale is estimated to be around 600 years old.
Bark Powderbark eucalyptus:
On the west coast of Australia is the home of the powderbark eucalyptus. The trees reach heights of 15 to 25 meters. They bloom from December to April and have a strikingly smooth bark in attractive pink-orange colors.
How to properly plant eucalyptus
The original home of the eucalyptus are the tropics and subtropics. Nevertheless, there is nothing against cultivation in our latitudes. Some species even tolerate light frosts. Eucalyptus gunnii, which even sub-zero temperatures can not harm, has proven to be a popular type for cultivation in the home garden. We'll tell you here what to consider when planting the blue rubber trees.
In order to do justice to the tropical plants, a bright and warm location is needed. The plants like direct sunlight. This is shown by a fast and attractive growth and a strong leaf color. Some species also tolerate freezing temperatures. Eucalyptus gunnii “Azura” is one of them. The variety tolerates temperatures down to -20 degrees. Resistance to light frosts only applies to outdoor plants. Container plants are more sensitive and need winter protection.
The eucalyptus tolerates partial shade. However, this is at the expense of the joy of growth and the pretty leaf coloring. A wind-protected location is also required. Wind and drafts do not get the tropical plants.
The ideal location in brief:
- full sun
The demands on the substrate are rather low. However, it should be a nutrient-rich soil. It is therefore advisable to enrich the soil with compost when planting and thus to ensure long-term organic fertilization of the plants. Since they do not tolerate waterlogging, you should provide a drainage of pottery or gravel. This is a must especially for container plants.
The ideal substrate in brief:
- Add compost
- Create drainage
Planting instructions for eucalyptus:
The best time to plant eucalyptus is early spring. To do this, select a mild and frost-free day and proceed as follows when planting:
- Select location.
- Loosen the soil.
- Dig out the planting hole.
- Mix compost into the substrate.
- Create drainage.
- Insert the plant.
- Fill in the substrate.
- Press down slightly on the bottom.
- Water the plant well.
Keep eucalyptus as a houseplant
The culture of eucalyptus is also possible as a houseplant. Here it is advisable to use Eucalyptus gunnii. This quite robust variety grows less quickly. This species grows less than 50 centimeters each year. Most species grow more than double in height each year and would therefore have to be cut back continuously to be suitable as a houseplant.
Care of the houseplant:
The plant also needs a bright sun in the room. At the ambient temperature, however, the blue rubber tree is tolerant. The eucalyptus will grow just as well at room temperature as it does in somewhat cooler rooms.
The plant needs sufficient moisture during the growing season. The floor should not dry out even in winter. Compost is also a suitable substrate for houseplants.
Cultivate eucalyptus as bonsai
Eucalyptus are particularly fond of growth, which does not make them appear easy as a candidate for bonsai education. However, the effort is worth it. The robust and frost-resistant Eucalyptus gunnii is particularly good as a bonsai. Upright forms are the most popular types of eucalyptus bonsai.
Care of the bonsai:
In summer, the bonsai can be given an outdoor sun spot. The hibernation is bright and at temperatures around 15 to 18 degrees. Provide sufficient water. The root ball should always feel moist. You can give bonsai fertilizers at weekly intervals during the growth phase, between April and August. Due to the rapid growth, you have to consistently follow the pruning. The bark of the trees is particularly sensitive. Wiring is therefore not advisable. The eucalyptus bonsai needs a larger planter every three years.
How to properly care for eucalyptus plants
Compared to comparable plants, the water requirement of the blue rubber tree is rather low. The hard-leaved leaves evaporate relatively little water. Nevertheless, you should water the eucalyptus moderately but regularly. The water requirement increases on hot summer days. The substrate should be able to dry between the individual waterings. This makes it easier to assess whether the plant really needs water. Because the plants do not tolerate waterlogging. In winter, the plants also need significantly less water, but should never dry out completely.
Preferably pour with rainwater. The eucalyptus does not tolerate calcareous tap water.
Mix in the compost in the potting soil, the young plants are provided with an effective long-term fertilizer and do not need any additional fertilizers in the first year after planting. Otherwise fertilizer must be administered during the growing season. Commercial liquid fertilizer is e.g. well suited. You should add these to the irrigation water every two weeks. When buying, make sure that the proportion of phosphorus and nitrogen is as low as possible. From August you should no longer fertilize.
What has clearly been missed in the giant eucalyptus, which is up to 100 meters high, is essential for the house or container plant. If the blue rubber trees are not to grow over our heads, a regular cut is essential. But this can be done without any problems, because the plants are very well tolerated by cutting. Cutting measures on plants in the open and on pots are preferably carried out in spring. If larger wounds occur, you should treat them with a wound closure agent. You must not prune the roots of the plants.
House plants can be trimmed all year round. Specially fast-growing species also several times. With eucalyptus gunnii, the scissors need to be used less often because the plant only grows about 40 centimeters per year.
The plants grow quite quickly, which results in regular repotting. Depending on the choice of the planter, the measure may also be necessary twice a year. Choose sufficiently large planters so that repotting is not necessary several times a year. You can tell from roots that are pushing out of the planter that the plant needs a larger container. When transplanting, you should take care of the root area. You must also completely cover the roots with the new substrate.
Some eucalyptus species are considered to be partially hardy. In our latitudes, however, the winters are usually too cold and rough to get by without the winter protection for the blue rubber tree. Small trees planted outdoors require winter protection made from garden fleece. You should also cover the root area with brushwood or leaves. Only Eucalyptus gunnii is considered to be quite robust and tolerates temperatures down to -12 degrees.
Container plants are generally to be hibernated indoors. The plants in the bucket are less robust and the frost would attack the sensitive root system. The winter quarters should be bright. Therefore, a winter garden is ideal as a wintering place. The temperatures should not drop below eight degrees. Houseplants can also overwinter warmer, but should then be watered as usual.
Detect and combat pests and diseases on the eucalyptus
The eucalyptus proves to be robust against diseases and pests. This should not least be due to the essential oils, which deter numerous pests. Nevertheless, aphids or spider mites can occasionally appear on the eucalyptus.
Especially in spring, aphids can be seen on the tips of the shoots. The common spider mite also occurs frequently. You can clearly see the pest infestation by the dark sooty fungus or by the cobweb-like network. Aphids can usually be eliminated without the use of chemical pest control. If the infestation is detected early, it can help to remove the pests with a water jet. If the plant takes an immersion bath in cold water for about a day, aphids are reliably killed even in the case of more infestation, whereas you do no harm to the plant itself. Treatment with soft soap solution or nettle slurry (instructions for nettle slurry) can also help with aphids and a spider mite infestation.
How can eucalyptus be propagated?
The propagation by sowing has proven itself with the blue rubber tree. The seeds can be obtained directly from existing plants or purchased from specialist retailers. Eucalyptus cultivated as a houseplant usually does not bloom and therefore does not form any seeds. Proceed as follows when sowing:
Sow the seeds in a damp sand-peat mixture. The seeds then need constant temperatures of 22 to 24 degrees for germination. In order to ensure this, it is advisable to place them in a nursery box. The germination time is about 3.5 weeks. If the first leaves appear, prick the young plants and transfer them to larger containers. Compost is suitable as a substrate. You can now treat the young plants as already described and will usually grow quickly into strong eucalyptus trees.