Presentation of the eucalyptus plant
The eucalyptus plant is part of the Myrtaceae. It includes a large number of species (more than 800) native to its area of origin, Australia, and found throughout the countries around the Mediterranean, Asia, South Africa, and Latin America. In our climate, a relatively small number are found in cultivation, because the genus Eucalyptus prefers warm areas to thrive.
Eucalyptus is either a fairly tall shrub with a bushy form, a small tree 4 to 8 m high, or a very large tree that can reach several dozen meters (50 to 90 m). The species proposed for our gardens remain between 10 and 30 m high.
The foliage of the eucalyptus plant is evergreen, aromatic, and leathery. It contains eucalyptol whose scent is a mixture of strong mint and camphor. This essential oil is used for its medicinal properties to relieve respiratory tract ailments, and aromatic to keep mosquitoes and biting insects away. The silvery-gray leaves with bluish highlights may be rounded when young and lanceolate as they age.
In spring or summer, umbels of cream-colored flowers appear, melliferous and slightly fragrant, followed by hard capsules containing seeds that have the same smell as the leaves. In the past, in some regions, these capsules were threaded into necklaces that were placed in cupboards to keep moths away, and around the neck to cure colds.
The tree’s vernacular name is “gum tree” because of the resin that can flow from the trunk. This smooth trunk peels off in strips each year, which produces an interesting decoration as the bark changes color. It sometimes has swellings at the collar and below the soil surface, which are similar to roots called lignotubers. These starch-filled lignotubers serve as reserve organs to ensure the survival of the species and can give rise to shoots.
Eucalyptus plant bark
The eucalyptus plant is remarkable for its two-tone bark and the silver of its foliage. How can you not fall under the spell of this tree capable of growing to more than 30 meters without any help? In the garden, as an isolated subject, in a group or lined up in a curtain, the eucalyptus plant brings with it a bit of Australia, it’s country of origin.
Where to plant it
The eucalyptus plant is an ornamental tree or shrub. In the garden, it can be planted as an isolated subject, grouped together or in a row to create a beautiful plant curtain. In seaside gardens, it should be planted more than 250 m from the shore, with a preference for low forms, sheltered from strong winds.
It will find its place ideally in a scene with a dominant white color with its silver, grey-green, or blue evergreen foliage. Its smooth bark has the particularity of falling every year in patches, the new bark and the old one still on the trunk giving a beautiful colored contrast. Its flowers are abundant, white, yellow, pink, or red, and very nectariferous. What’s more, some species are fragrant and the eucalyptus plant keeps mosquitoes away!
Eucalyptus plant grows in all climates as long as it is well protected from frosts (even very light ones) and that it benefits from good sunshine. The eucalyptus is able to resist drought because its roots gorge themselves with water. Thus, this tree will do particularly well in the warm areas of the Mediterranean coast where it is rustic, and those very sheltered from the Breton coasts.
In addition to its decorative use in gardens in isolated plantations or hedges, florists use the foliage of certain varieties (E. Globulus, E.Gunii, E. Cinerea…) as greenery as well as the decorative fruits in the composition of bouquets.
What type of soil
Eucalyptus plant grows best in well-drained, fairly dry, and deep soil. It also tolerates dry and rocky soils very well, even growing rapidly in poor and degraded soil. The height of the eucalyptus at maturity varies according to the species from 8 to 30 m, even more.
In the ground, once adult, the eucalyptus plant requires little or no maintenance. When young, regular and copious watering will be necessary during periods of heat or drought. For potted plants, water regularly while allowing the substrate to dry between two waterings. Reduce the watering in winter to avoid prolonged drying out of the substrate.
Mulch the base in winter if you live in a region subject to frost. In spring, a vegetal mulch will enrich the soil and keep it fresh between two waterings. In the first five years, it is imperative to stake the plant to prevent it from uprooting in the slightest wind. Some varieties of eucalyptus, mainly those grown in pots, must be pruned regularly.
The eucalyptus plant is not pruned, its growth habit remains balanced during its growth. Fertilizer is not necessary, this tree knows how to do without it, even in very poor soil. Warning: do not use its dead leaves as mulch or for compost, they are toxic.
Diseases, pests and parasites of the Eucalyptus plant
Eucalyptus trees are naturally resistant to pests (thanks to their essence) as well as to diseases in general, with the exception of “eucalyptus gall” which is a cryptogamic disease due to the laying of eggs in the parenchyma of the leaves by a small Hymenoptera (“gall wasp” of about 1 mm) Ophelimus eucalypti. It is especially widespread in the Mediterranean regions.
This gall results in numerous small blisters with tiny holes on the surface of the leaves, which quickly turn yellow before drying.
The only known effective treatment consists in cutting and burning the branches with affected leaves. It should be implemented as soon as possible, but is difficult to achieve for larger trees.
A little botany
From the Myrtaceae family (the myrtle family), the genus Eucalyptus counts 600 species, native to Australia, southern Papua New Guinea, and the southern Philippines.
Eucalyptus plant provides wood for heating and paper making. It is reputed to be effective in clearing bronchial tubes and calming coughs. It also has, in external use, healing and antiseptic properties.
The tallest trees on Earth are eucalyptus: the record of 132 meters is held by an Australian eucalyptus, beating the 113 m record of the Redwood.
The evergreen leaves in our climate are covered with small glands filled with essential oil of the eucalyptus plant which makes them very fragrant. For some varieties, they have an almost round juvenile shape and are attached directly to the twigs while later they become lanceolate and narrow at the end of a petiole. Their color is then glaucous, green-bright or silver. Their port is sometimes upright and most often hanging.
However, for other varieties, especially those cultivated in pots, keep their juvenile form for a long time. Finally, some of the varieties have all their life green and shining foliage. The hermaphroditic flowers have numerous stamens which are first enclosed under a lid that opens and releases them at maturity. They are often of a white-cream color but sometimes also pink or red. They usually appear from the fifth year, either in summer or in winter according to the species. They produce woody, often blue-green, capsule-shaped fruits.
Finally, since the 19th century when it was brought back from Australia, the medicinal use of its leaves and its essence has spread widely for the treatment of ENT ailments. Its properties are widely recognized, whether in phytotherapy for E. globulus (in the form of infusion or capsules of leaf powder), or in aromatherapy with E. Radiata, E. citriodora, E. dives (in the form of essential oil in drops, aerosols), or entering the composition of several medicines especially intended to treat coughs, sore throats and other affections of the respiratory tract (syrups, suppositories, solutions and sticks for inhalations, pastilles to be sucked… the balsams being also used in frictions or massages). Traditionally, its leaf decoctions are also used to sanitize and perfume a room during winter epidemics.
The main active ingredient is eucalyptol, present in varying proportions depending on the species. Its antiseptic and decongestant properties are usually used in combination with menthol.
Good to know: eucalyptus plant essence is obtained by steam distillation like lavender essence and it takes about 50 kg of dry E. globulus plant to obtain 1 liter of the essence.
Eucalyptus wood is widely used in tropical regions to make garden furniture as well as to produce paper pulp. Eucalyptus plant grows quickly, reproduces easily thanks to its numerous seeds, and is quite resistant to fire thanks to the presence of lignotubers. It is also used to recolonize land devastated by the fire with beautiful forests.
- Height at maturity: 15-20 m Width at maturity: 5-6 m
- Origin: Tasmania
- Hardiness: hardy Soil composition: normal, sandy, heather, rich in humus
- Soil PH: neutral, acid
- Soil moisture: normal, dry
- Exposure: sun, half-shade
- Use in garden: bedding, seaside, isolated
- Leaf color: green, blue
- Foliage: evergreen
- Flower color: white
- Flowering time: July-August
- Planting time: year-round (frost-free)
- Care level: very easy
- Watering: normal
- Attributes: fragrant
- Use: garden Fruits: none
- Season of interest: spring, summer, fall, winter
- Flower shape: umbel
Among the species to be grown in our climates, some are suitable for medium-sized gardens, but most are recommended for large gardens with the necessary area to showcase these remarkable trees.
Growth habit and size: Erect growth habit to 15 to 20 m high depending on growing conditions. The crown spreads with age and can reach more than 5 m wide. The young leaves are rounded then lengthen and become pointed. Small ovoid fruits.
Qualities: young red stems, bluish-silver foliage, and green and whitebark exfoliating each year in long strips that show the new yellow or pinkish bark before it turns green. Very fast-growing. Hardy to -15 °C.
Growth habit and size: slender habit on 20 to 30 m high. Vigorous tree. Leaves very long and pointed, dark green with a yellow midrib. Blooms with white pompons in spring.
Qualities: called white mountain gum, this eucalyptus plant has a changing bark, white when young to pink when it is cold. Very fast growth. Hardy to -15 °C.
Growth habit and size: erect with a rounded crown 6 to 8 m high. Large, green, and turning grey, sickle-shaped leaves. To be planted in well-drained soil and sunny exposure.
Qualities: small, very decorative tree with white bark streaked with green. Called snow gum, it tolerates poor soils and cold winters with temperatures around -15 to -20 °C.
Port and size: slender port then spread out to 15 m high. Leaves bluish-green, early white pompom-shaped flowers in spring.
Qualities: hardy to -15 °C and more resistant to wind. Slower growth than other species.
Growth habit and size: very large tree with a columnar habit over 30 m high. Massive trunk. Flowers in cream pompons in May-June, narrow and elongated green leaves.
Qualities: called blue gum tree, this eucalyptus plant is one of the species used in phytotherapy for its essential oil. The leaves can be used for infusions. The very fast growth of 2 m per year, it reaches 20 m high in 10 years. Hardy to -8 °C.