Eucalyptus trees, or gum trees as most of its species are called, are famous for their round, silver leaves. These are marked by a distinctive fragrant oil and leathery feel. Due to the aromatic nature of the plant, it is commonly used in fresh and dried floral arrangements.
The aromatic eucalyptus oil provides several herbal benefits useful in cleaning and medicinal products.
Where Can You Find Eucalyptus Trees?
The Eucalyptus tree is hardy and will do well within USDA plant hardiness zone 8 to 11. However, in other areas, the Australian gum tree species can be planted as annual plants grown from seed.
Some Eucalyptus species can grow to heights of up to 60 feet or more during their life cycle. While others remain shrubs under 3 feet tall. On average, eucalyptus trees grow between 10 and 15 feet each year.
What Are the Different Types of Eucalyptus?
There are more than 700 species and subspecies of eucalyptuses. Most of them are gum trees Australia and Tasmania know well as they come from there.
Although many varieties of the plant exist, some are more popular than others, especially in the United States.
Eucalyptus globulus, or ‘blue gum’, for instance, is the most common variety. E. globulus is widely grown around the world because it is highly adaptable and therefore often used in forestry plantations. This is likely the variety you will find at your local tree nursery.
Eucalyptus globulus can grow to heights of between 150-180 feet. Blue gum has a straight trunk for up to two-thirds of its total height, with a well-developed crown at the top.
The E. globulus has glossy, dark green leaves that are thick and leathery on older branches. But the younger leaves of the blue gum eucalyptus are whitish, waxy, and arranged on opposite pairs.
The eucalyptus trees come in a wide variety of sizes. The different species fall into several tree types with the most popular being:
1. Marlock Eucalyptus
Marlock Eucalyptus grows best in zones 7-8 on the USDA plant hardiness zone map.
Eucalyptus platypus, commonly known as rounded-leave moort, is a small tree with a perfect structure for the modern gardener. It grows well in sandy, loamy, and even clay-rich soil, making it adaptable to most areas.
Moort grows from 5-33 feet in height on a single stem and form thickets. The dense foliage on this type of eucalyptus makes it ideal for ornamental purposes.
2. Mallet Eucalyptus
Mallet eucalyptus is a variety of eucalyptus species with a slender trunk and branches angled upwards with open spaces between them.
The mallet variety does well within zones 9-10 on the USDA plant hardiness scale.
One of the most popular varieties from this type of species is the Eucalyptus astringens. These trees grow to heights of between 5-49 feet tall with lance-shaped leaves. They have pendulous flower buds, usually in clusters of seven, with cream flowers.
The wood from these trees is great for timber and firewood. This tree’s bark contains about 40% tannin. This makes it suitable for use in tanning leather and making adhesives.
3. Mallee Eucalyptus
Mallee is a species of eucalyptus characterized by low-growing shrubs. Malles have multiple stems and grow to about 10 feet, though they can reach up to 25 if the conditions are favorable.
One of the most common varieties of mallee is the Eucalyptus erythronema.
E. erythronema, popularly known as red-flowered mallee, is one of the species of Eucalyptus native to Western Australia.
It grows to heights of between 7-20 feet and can be single or multi-stemmed. It has white bark, with green younger bark covered in a pinkish talc-like powder.
Its flowers are usually red, but they can be pink, yellow or creamy white.
The Eucalyptus erythronema makes for a beautiful ornamental plant. You can also use it for honey production, tanning, or as a screening plant.
Evidently, the different types of eucalyptus trees have similarities which can make telling them apart difficult. Here is a quick comparison between the three major types of eucalyptus species to help you along:
Eucalyptus Tree Varieties to Try
Eucalyptus gunnii has interesting cream and brown bark and can grow to 80 feet tall. Young trees produce bluish-gray leaves, while older trees produce silverfish-green leaves.
Eucalyptus cinerea grows 25 to 60 feet tall in warm climates, but it is often grown as an annual shrub in colder climates, where it reaches 6 to 8 feet tall in one season. This specimen has a peeling red or cinnamon-colored bark.
Eucalyptus dalrympleana grows 50 to 70 feet tall and has striking cream-colored bark. Unlike most eucalyptus trees, it produces slender, willow-like leaves. The leaves are aromatic, but they lack the rounded shape eucalyptus are known for.
Eucalyptus deglupta is a spectacular tree, also known as rainbow eucalyptus. The eucalyptus bark is known for its beauty. It’s a gum that has a description to match the ribbons of color on its bark.
What are Eucalyptus Trees Used for?
Eucalyptus trees are more commonly known for their unmistakable scent, but they have various uses. The plant species make excellent shade trees. They can serve multiple purposes in different fields, including:
Forest Restoration and Fauna Uses
The eucalyptus tree is planted in many areas around the world where deforestation is a major concern. Thus it helps restore the Earth’s health and fight urgent issues like climate change.
The planting of eucalyptus trees in forests also helps fauna around them thrive. These trees are used as a source of food and shelter by creatures like:
- Koalas: These marsupial herbivores flourish in a eucalyptus forest. They’re found entirely along the coasts of southern and eastern Australia and dwell in eucalyptus trees. Koalas feed on the leaves among other food by grabbing branches using their opposable thumbs.
- Common Wombats: These creatures are closely related to koalas. Unlike their close relatives, however, wombats, are generally terrestrial animals. This means that they’re more likely to be found on the ground than tree-hugging koalas. Where they do share an important similarity is in their choice of food. Wombats and koalas regularly compete for eucalyptus leaves.
- Greater Gliders: These tiny creatures get their name from their ability to glide through considerable lengths. Like koalas, these marsupials live in eucalyptus trees and consume their leaves.
One downside of afforestation with these Australian native plants is that it can harm other species. The E. globulus’ bark and leaves are toxic to humans and other non-marsupial species when consumed as is.
“If the bark or leaves are eaten, nausea, vomiting, and diarrhea may occur. If large enough quantities are eaten, it may cause the person or animal to lapse into a coma.” — SF Gate
Bird species are also negatively impacted by gum tree species. One study by ScienceDirect showed that such plantations lead to a decrease in the variety of avian species.
As well as its afforestation purposes, the eucalyptus tree is often used for its wood in an eucalyptus plantation. A eucalyptus tree’s wood is known to be very resistant to termites and deterioration. The tree can even last up to a decade in damp surroundings without rotting. Often used as an environment windbreak in North America landscape, but eucalyptus stands can be a fire risk.
Eucalyptus trees are convenient to use in carpentry as they’re effortless to polish, sand and cut through. Different parts of the tree also appeal to carpenters and furniture enthusiasts:
- Its sapwood has a pale color and captivating patterns.
- Its heartwood has a crimson color which gets darker as it ages.
Eucalyptus trees are often used in construction as timber for:
- Wooden bowls
Eucalyptus oil is used for its calming and refreshing aroma. Essential oils and compounds are therefore extracted from this tree species for the purposes of:
- Stress management
- Sleep therapy
- Energy stimulation
You’re bound to find extracts in most massage parlors and places of relaxation.
Another widely-renowned use of its essential oil lies in its health recovery benefits. There’s a wide variety of uses for the tree’s oil, including:
A number of herbal remedies include relief from symptoms like:
- The common cold
- Respiratory tract infection
- Nose congestion
- Sore throats
In such cases, the plant is used in the form of boiled eucalyptus leaves, ointment, and/or vapor.
Some researchers believe that the ointment from eucalyptus species is analgesic. This means that it helps in pain relief. It can be used topically to soften up muscles and alleviate joint aches quickly. Eucalyptus oil is also commonly used by patients who have arthritis.
Insecticide and Repellent
Eucalyptus is also great at repelling insect pests and killing them. According to MedicalNewsToday:
“In 1948, the United States officially registered eucalyptus oil as an insecticide and miticide, for killing mites and ticks.
Oil of lemon eucalyptus is recommended by some as an insect repellant; it is effective at keeping mosquitoes away.”
Eucalyptus Products in Dental Protection
You’ll find toothpastes, mouthwashes and even gum with extracts in stores. And for good reason, the plant has antibacterial and antimicrobial properties. This means that it can effectively protect against bacteria that induce issues like tooth decay.
How to Plant Eucalyptus
All eucalyptus tree varieties require full sun, but some species will tolerate partial shade. They adapt well to a wide range of soil in different climates provided it is well-drained.
When planting eucalyptus trees, do so in mid to late spring or fall, depending on your location and climate. Dig the hole slightly larger than the root ball and take extra care with the roots during planting.
Eucalyptus roots are sensitive, and it’s best to leave them undisturbed.
You can also grow eucalyptus as a potted perennial until it grows too big. In this case, you can donate it to the park or move it to your backyard.
Ideal eucalyptus varieties for growing in containers include:
- Eucalyptus archeri
- Eucalyptus crenulata
- Eucalyptus coccifera
- Eucalyptus nicholii
- Eucalyptus parviflora
- Eucalyptus vernicosa
How to Grow Eucalyptus in a Container
When planting eucalypt species in a container, it is best to start with the largest pot available.
When the plant outgrows the pot, you are probably better off discarding it and starting over with a new seedling. Eucalyptus plants that are grown in pots hardly ever transplant well into the ground.
In warmer weather, you can leave the potted eucalyptus outside and bring it in before the first frost in fall.
When you do this, keep in mind that eucalyptus requires full sun to thrive. Pick a sunny, sheltered location where you can easily water it, perhaps next to a south-facing window.
If you want to grow your plant from the seeds, there are a few notes you have to keep in mind, the most important of which is that eucalyptus tree seeds require a stratification period.
How Do You Stratify Eucalyptus Seeds?
For stratification to be successful, it needs to mimic the exact conditions the seeds naturally require to break dormancy. For eucalyptus seeds, this means cold treatment to match the time the seeds would spend on the ground over winter.
The stratification process usually takes some time, so you will need to plan ahead.
When ready, place your seeds in a sealable bag or container, pop it in the refrigerator and leave it there for two months to soften the seed coat.
Plan this so they are ready after the last expected frost, maybe around the middle of February. You can confirm the dates on your local meteorological department’s website.
When the two months are up, sow the seeds in peat pots (if you plan on moving them to the garden) or in your desired indoor pot to help curb plant transplant shock.
Make sure to use porous potting soil with lots of pearlite when planting eucalyptus in a container. You can cover the seeds with a light dusting of horticultural sand to keep them warm and moist as they germinate.
Mist the seeds regularly, roughly every 1-2 days, to settle the soil and keep it moist without drenching it.
Remember to keep the seeds warm at this stage. You can do this by moving the pot to a warmer part of your house. You can even place the pot on a heating pad to keep the seeds warm as they germinate.
After germination, keep the young species in full sun, preferably in a protected location, and water them with ease. The young plants have shallow roots. They can easily break or get toppled over by the wind or curious toddlers and pets.
And although the tree can tolerate drought, it will grow better with regular moisture.
How to Care for Your Eucalyptus Plant
Eucalyptus trees don’t need a lot of care, especially when growing out in the yard. The trees usually maintain themselves reasonably well.
Potted eucalyptus plants require regular watering, especially during the warmer seasons. Eucalyptus is drought-resistant and will rebound from slight wilt, but may not if it is allowed to wither.
You should also avoid overwatering the plant. A good rule of thumb is to allow the soil to dry out somewhat between watering. Perhaps once a week.
Fertilizer is not necessary for trees growing in the ground, as eucalyptus does not appreciate phosphorus. However, for potted plants, you may need to use low-phosphorus, slow-releasing fertilizer.
Additionally, tree care includes regular pruning to control growth and height. This is handy, especially for the indoor species to regulate the shape and size of the plant to keep it a suitable size for indoor use.
For the outdoor species, eucalyptus trees can produce a lot of litter in the form of leaves, peeling bark, and branches. The bark and leaves are a fire hazard and need regular raking, especially in the fall.
Planting these Australian native species where there’s lots of moisture can lead to them spreading. Eucalyptuses are invasive species and already make up 77% of Australia’s forests.
What Happens to the Bark on Eucalyptus Trees?
One similarity between most invasive species is that their bark sheds once a year. This happens because it dries up and dies off, ultimately creating a remarkable peeling effect. Shedding leads to a display of orange-yellow patterns as one bark distinguishes itself from the other.
This yearly bark-shedding process also has health benefits for the eucalyptus trees. According to Gardening Know-How:
“As the tree sheds its bark, it also sheds any mosses, lichens, fungi, and parasites that may live on the bark. Some peeling bark can perform photosynthesis, contributing to the rapid growth and overall health of the tree.”
Eucalyptus Pests and Diseases
In some areas, eucalyptus groves suffer from gall wasp infestations. These are tiny grubs that form pinkish-brown bumps called galls on the stems and leaves.
You can control this pest by removing and destroying infected leaves in the fall. You can also spray your smaller or potted species with pesticides, but this can be a bit of a problem for larger trees.
The eucalyptus trees can also contract canker disease. This is an infection caused by the fungus Cryphonectria cubensis.
The infection kills young trees, usually within their first two years of life, by girdling the base of the stems. The trees then wilt and die suddenly in the summer heat and those that don’t will display cracked bark and swollen bases.
The trees get infected with canker when rain or wind disperse the fungus spores and they fester in the wound.
Therefore, the most effective canker treatment involves avoiding any physical damage to the plant. In case of accidental wounding, sanitary protection of the wound.
Several varieties of eucalyptus trees are more prone to canker infections. These include:
- Eucalyptus camaldulensis
- Eucalyptus grandis
- Eucalyptus saligna
- Eucalyptus tereticornis
You should avoid planting these trees in areas with extreme heat and heavy rainfall, where the fungus thrives.
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