Eucalyptus, an evergreen tree native to Australia, is perhaps best known as a favorite food for koalas. In Australia, the fast-growing trees may reach massive heights of 300 feet with a hefty circumference of more than 24 feet.1 Other varieties take the form of short, bushy plants, all of them with a characteristic pungent aroma.
Eucalypti are also known as gum trees or stringybark trees, and in addition to being a staple food for koalas, are prized for use as fuel and timber, and are valued for medicinal uses in Australia and around the globe. In the U.S., eucalyptus plants are only suitable for U.S. Department of Agriculture (USDA) Hardiness Zones 8 to 11 — if you plan on planting it outside.
However, this plant grows well in containers, which means even if you live in a cooler climate, you can have your own eucalyptus tree as long as you bring it indoors for the winter. Some people even prefer to grow eucalyptus as an indoor plant, and because it’s so fast-growing, you can also use it as an annual.
Why Grow Eucalyptus?
Eucalyptus has a wonderful menthol-like scent that’s released from the foliage when it’s rubbed. Simply cutting and drying the leaves, then placing them in a bowl in your home will create a natural, fresh-smelling potpourri. Eucalyptus is also a favorite among crafters, with its decorative foliage creating a perfect addition to centerpieces and arrangements.
Eucalyptus branches are easily dried by hanging them upside down in bunches. The leaves are “ready” when they’re leathery or crispy feeling. You can even preserve them by immersing them in a jar with about 3 inches of a glycerin and water solution. For the solution, mix one part glycerin with two parts boiling water. The Spruce suggests:2
“Keep the jar in a cool, dark place and inspect the plants weekly. Add more liquid as needed to keep it at the optimum level. It may take anywhere between one and eight weeks for all the leaves to change color. When they have, the process is complete. Remove the eucalyptus branches, pat them dry with a paper towel, and hang them upside down for two to three days before using.”
The leaves, bark and roots of eucalyptus also contain medicinal eucalyptus oil, which is widely used as an antiseptic, in oral care products and cosmetics, in flavorings and even in industrial solvents.
Eucalyptus Has Medicinal Properties
You may be interested to know that eucalyptus is a common plant used in complementary medicine, in part because it has strong antimicrobial properties. For instance, eucalyptus leaf extract has antibacterial effects against pathogens commonly involved in respiratory tract infections.3
It may even work synergistically with conventional antibiotics to fight multidrug-resistant bacteria.4 In a study published in the Asian Pacific Journal of Tropical Biomedicine (APJTB), researchers discovered that essential oil extracted from eucalyptus globulus leaves is particularly effective against common strains of bacteria, such as E. coli and Staphylococcus aureus.5
Herbal infusions of eucalyptus can be used as a chest rub, skin antiseptic or as a steam inhalation. The vapor from eucalyptus oil is often recommended for use as a decongestant for colds and bronchitis. Eucalyptus oil can also be added to a diffuser for air freshening or congestion relief. It’s also an effective insect repellant.
Eucalyptus oil can also be added to bathwater and is said to ease pain6 and inflammation. The essential oil extract is also immune boosting, with researchers suggesting it could “… drive development of a possible new family of immunoregulatory agents, useful as adjuvant in immunosuppressive pathologies, in infectious disease and after tumor chemotherapy.”7
When added to oral care products, eucalyptus may be effective against bacteria that contribute to tooth decay. One study even looked into the effects of eucalyptus extract chewing gum, which was found to promote periodontal health and significantly reduce plaque accumulation and other measures of dental health.8
Different Eucalyptus Varieties
Eucalyptus comes in hundreds of different varieties. Some grow into towering trees when mature while others can be maintained as bushy shrubs. If you have a eucalyptus plant, be generous with pruning and cutting it back, as it will help the plant to become fuller rather than tall and leggy (plus, you’ll probably want to make use of all of the cuttings).
The first step to planting is to choose the best variety for your needs. Below are some eucalyptus varieties that vary based on their leaf size and shape, primary uses and preferred growing habits:
Eucalyptus gunnii — “Silver drop” produces blue-gray leaves when young and silver-green leaves when mature.
This variety may grow to 80 feet tall and has brown- and cream-colored bark. However, it is popular as an annual, as it will grow about 2 to 3 feet tall and wide.
Eucalyptus globulus — This species (also known as Tasmanian blue gum) is the top choice for creating eucalyptus essential oil and is the ingredient used for various eucalyptus products as well.
Eucalyptus radiate — Also known as “narrow-leaved peppermint,” it is known for its refreshing aroma.
Eucalyptus cinerea (silver dollar) — While this variety can be grown as a tree outdoors in warm climates, it also works well as an annual and can reach up to 8 feet in one season.
It’s also known for its cinnamon-colored, peeling bark.9
Eucalyptus polybractea — Also known as “blue mallee,” it is high in cineole, which is a colorless liquid terpene with an odor similar to camphor.
It has long, narrow willow-like leaves that are blue-green and frosted in color.
Eucalyptus deglupta — ‘Rainbow eucalyptus’ has rainbow colored bark that sheds throughout the year.
It is the only eucalyptus variant that grows in the Northern Hemisphere and is mainly used for decorative and shade purposes.
Tips for Growing Eucalyptus
If you plan to plant eucalyptus outdoors, be aware that these hardy, fast growers are sometimes considered invasive. There’s even speculation that they may release a chemical into the soil that stops competing plants from growing.10 The trees also have exfoliating bark that, while showy and quite impressive, can accumulate on the ground, which might not be desirable in some locations.
They’re also considered to be fire hazards in some locales, as their high oil content makes them prone to burning quickly. Outdoors, eucalyptus will need a sunny spot that’s protected from drafts along with regular watering. When grown in its ideal conditions, eucalyptus will also produce blossoms that are a favorite among bees.11
Many home gardeners will prefer to grow eucalyptus in a container or as a houseplant. Some varieties that thrive in container gardens include lemon-scented gum (Eucalyptus citriodora), argyle-apple (Eucalyptus cinerea), silver-dollar gum (Eucalyptus perriniana) and mountain gum (Eucalyptus dalrympleana).12
You can leave potted eucalypti outdoors in the summer, but be prepared to bring them inside when the weather gets cool, and definitely before the first frost. The plant can be cut back and stored in a cool area (such as a basement) to overwinter. If temperatures are below about 46 degrees F, you only need to water the eucalyptus sparingly.
If you prefer, and your home is warm with access to a bright (preferably south-facing) window, eucalyptus can continue to grow over the winter, with higher temperatures leading to faster growth.13 You’ll need to water it regularly in this case.
Be aware that your eucalyptus plant will probably outgrow its container at some point, so you’ll need to either plant it outdoors at that point or move it to a larger container (do this in the spring). The alternative is to regard eucalyptus as strictly an annual that you start new each season.
You may choose to purchase a eucalyptus plant that’s already established, but it can also be grown quite readily from seed. Sow them shallowly in the spring or late spring into the container in which you plan to keep the plant. Cover the potting mixture with sphagnum moss and keep the seeds in a warm spot (at least 60 degrees F).14
You’ll need to mist the seeds regularly to keep them damp, Once the seedlings have established themselves as young trees, they can be moved outdoors (provided it’s summer).
Is Eucalyptus Poisonous?
If ingested in large enough quantities, eucalyptus is toxic to dogs, cats and horses. If you’re wondering how koalas can eat it, they are the only mammal that can survive on a diet consisting of eucalyptus alone.
While other animals cannot digest eucalyptus leaves, because too much of it can be poisonous, the koala has the advantage of having a specialized caecum, which is a section in the digestive tract containing millions of beneficial bacteria that can break down the eucalyptus leaves safely.15
In humans, it’s advised that you consult your health care practitioner before consuming eucalyptus, as excess consumption can cause digestive problems, such as vomiting, diarrhea and nausea. For instance, while you may enjoy using your plant to make eucalyptus tea,16 you should limit consumption to a maximum of two to three cups daily:
- 1 cup of water
- 1/2 teaspoon of dried eucalyptus leaves per cup of water
- Raw, organic honey to taste (optional)
- Bring the water to a boil.
- Place the leaves in the teapot.
- Pour the boiling water and let the tea brew for five to 10 minutes.
- Add honey to taste (optional).
- Serve and enjoy.
When applying eucalyptus oil to your skin, be sure to dilute it with a carrier oil. In general, adults should not take eucalyptus oil orally except under a doctor’s supervision, and this oil mustn’t be given to children, especially those under 2 years old. You may, however, add very diluted eucalyptus oil to a gargle to use as a soothing remedy for sore throat.
How to Use Eucalyptus Leaves in Your Home
If you grow eucalyptus, you’ll probably be very interested in what to do with all of those beautiful leaves and branches. Most simply, snip some stalks from the plant, place them in a vase and use them as a centerpiece or mantle decoration.
You can also add eucalyptus leaves to a bowl or sachet and use them around your home to repel insects or act as an air freshener. You can also boil water and add eucalyptus leaves to the pot. The steam that’s released will add a pleasant aroma to your home.
For congestion relief, you can (carefully to avoid burning) also place a towel loosely over your head to create a tent and inhale the steam. With the many varied uses, from aesthetic to medicinal, and the ease of growing, eucalyptus is one plant you’ll likely find yourself coming back to for years to come.