Travel just a little bit of Australia, and you will see just how many varieties of the iconic Eucalyptus trees there are. They have names that show off their features, like the ghost gum with its pure white bark, the squiggly gum, with patterns covering the bark like a child passed by with a crayon, or the rainbow gum, with its stripy bark in all the colors of the Australian landscape.
These giant trees are also the main habitat for Australian wildlife and the only diet of the koala. The leaves of eucalyptus are extremely toxic to most animals, but koalas can eat up to 2 pounds when they are not sleeping for 18 hours a day. Funnily, they are picky eaters, choosing only 50 types of the 800 eucalyptus varieties available to them. Because of bushfires and human intervention, koalas are losing their habitat rapidly.
Eucalyptus in Australia even has its own national day. March 23rd is National Eucalyptus Day, to raise awareness of the importance of these trees in Australian culture.
In the US, eucalyptus varieties are prized for floral arranging, offering crisp scents and beautiful gray-blue shades that offer a perfect foil for colorful flowers.
This article will give you an outline of how to grow eucalyptus at home, with some fascinating characteristics and features along the way.
Overview
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What is it?
Eucalyptus range from small shrubs to giant trees, with heights from 33 to over 300 feet.
The more than 800 varieties of Eucalyptus belong to the Myrtle family. These can vary in size from small shrubs of a few feet. Medium trees can grow to 33 feet in height, and giant trees may reach more than 300 feet.
Native area
Eucalypts, abundant in Australia, were introduced worldwide for fast-growth and timber.
The majority of the varieties of eucalypt in Australia grow in massive native forests, with others cultivated for gardens and as indoor plants. A few others grow in Malaysia and the Philippines.
In many other countries, it is an introduced species – particularly the blue gum tree Eucalyptus globulus – for its ability to grow fast and produce excellent wood as a timber crop.
One of the downfalls of using gum trees as a crop is the staggering amount of water they need each day. One tree can use up to 200 gallons of water a day.
They also produce compounds called allelopathic chemicals, much like black walnut trees, that leach into the soil and inhibit the growth of any other plants nearby. You will often see monocultures of eucalypts because of this factor. It’s not surprising, then, that many countries have declared them alien invasive plants.
Characteristics
Eucalyptus trees feature varied bark, including peeling, and their leaves, a source of oil, range in color and shape.
The bark of eucalyptus trees varies greatly between varieties. Some are smooth, Some rough, some mottled, some stripy in many variations of color. The bark peels back each season to reveal what’s underneath. These look like the squiggles of a moth making its way up the trunk, turning to a lighter green, bright yellow, or orange tinge that transforms its look. This peeling bark is one of the characteristics of the species. Some bark will peel back in long strands, giving it an iconic look.
The leaves are the main source of essential oil and emit the famous fragrance when you crush them. The leaves of younger trees are round with no stalks. They mostly range from blue-green to blue-grey to silver in color.
Varieties
As we mentioned, there are over 800 species of this amazing tree. The most common leaves for wedding flowers or floristry are from the following varieties:
Silver Dollar Eucalyptus
This eucalyptus variety is known for its distinctive, round, silvery-blue foliage.
Silver dollar eucalyptus is a soft grey with round, sparse leaves. It has a refreshing, minty scent and smooth leaves favored as a backdrop for colorful flowers in professional arrangements.
Baby Blue Eucalyptus
‘The silvery-blue leaves of ‘Baby Blue’ Eucalyptus shine in bouquets.
‘Baby Blue’ eucalyptus has round leaves that look like they have been threaded onto stalks in a light grey. It features tightly packed, long arching stems. The stems are robust and can last for weeks in cut flower bouquets. This species isn’t difficult to start from seed.
Gunni Eucalyptus
This Eucalyptus, with its gray-green leaves, is prized for its ornamental value.
The bushy leafy stems of ‘Gunni’ eucalyptus are covered in egg-shaped to pointy leaves in a blue-green color. The lighter, airy feel of this variety makes it a popular choice for bouquet filler. This type is perfect to add lots of texture to an arrangement.
Spiral Eucalyptus
This eucalyptus is distinctive for its twisted, spiral-shaped leaves and aromatic properties.
‘Spiral’ eucalyptus features stiff, rounded leaves that form a spiral along stems in a lovely greyish blue. If you’d like a natural air freshener for your home, this species will fill your room with a fresh and crisp scent. The long stems are perfect for adding height and drama to floral arrangements.
Seeded Eucalyptus
This charming Eucalyptus is known for its decorative seed pods and feathery foliage.
Seeded eucalyptus has blueish-green, round to long leaves with clusters of seed pods as the main attraction. With a wilder and more natural look, it’s a nice complement to informal garden bouquets.
Willow Eucalyptus
This tree features long, drooping branches with narrow, willow-like leaves, prized decoratively.
‘Willow’ eucalyptus has narrow, long, drooping leaves like a willow. They are dark greenish-grey with lighter undersides.
Most eucalypts have very distinctive flowers and fruit. The flowers have no petals, but a whole bunch of fluffy-looking stamens are grouped like puff balls. These burst from the base cup-shaped base of the flower. They come in colors ranging from white, cream, pink, and red, and they are bee magnets.
The fruit is formed at the base of the flowers. These woody capsules, sometimes referred to as gum nuts, develop to release seed.
Planting
Before planting eucalyptus trees, consider invasiveness, allelopathic effects, space requirements, water, and nutrients.
Before planting any eucalyptus tree in the garden, consider the following:
- Some varieties have been declared invasive in states like California and Hawaii, with other states doing investigations into the species. In other parts of the world, they are also a problem plant and, in some countries, they have been banned.
- Their allelopathic tendencies may be harmful to plants in the vicinity of the tree, which may leave some bare, unproductive patches in your garden.
- Most varieties grow big, so you will need enough space for them to grow.
- Finally, certain varieties use up a lot of water and nutrients from the soil.
If you are willing to look past all that, let’s look at how to grow them outdoors. Alternatively, skip to the part where you can grow them in containers indoors.
How to grow
Plant eucalyptus in the spring or in the fall and give them at least six to eight feet of space to grow if choosing a shrub or a tree eight to ten feet. Larger trees need much more space and are best planted in sweeping open areas. Give the roots in the nursery container a good soaking of water before you begin planting.
Light
These trees thrive in full sun, requiring a minimum of 10 hours for optimal growth.
Eucalypts like full sun. It takes at least 10 hours of daily sunlight for most varieties to grow sturdy trunks. Sunlight also ensures the trees have a good shape and healthy leaves.
Soil
Eucalypts thrive in well-drained soil, preferring sandy or loamy textures for growth.
Well-draining soil is essential. Provide slightly acidic soil with a pH of 5.5 – 6.5. If your soil is alkaline or retains a lot of water, like heavy clay, you can amend it to increase drainage and add acidity. Agricultural sand and perlite break up and aerate heavy soils. Compost assists with better nutrient exchange and retention in sandier soils.
Water
Eucalypts require frequent deep watering, especially weekly without rain.
As mentioned before, some of these trees like lots of water. Others resist drought when mature. Young trees especially will need watering deeply at least once a week when it’s not raining. Once established, the trees will go a while without water, but if the leaves start drooping madly and falling off, up the water schedule. Adding a layer of mulch around the base of the plants will preserve water.
Fertilizing
Eucalypts generally require minimal fertilization, as they adapt well to nutrient-poor soils.
Outdoor plants need no extra feeding. They are highly adaptable to nutrient-poor soils and don’t require fertilization to grow. You don’t want to give them extra nutrients and have either over or under-performance as a result.
Maintenance
Regular pruning maintains shape in fast-growing eucalyptus.
Pruning regularly will maintain a pleasing shape. Eucalyptus trees are fast growers, so keep an eye on out-of-control branches and leaves. After a couple of years, you can start pruning away the lower branches to give the plant a better shape.
You can also choose to coppice by cutting it back severely so that it bushes out and produces new lush foliage. This way, you always have a load of new leaves. Certain eucalypts also make good hedging plants, which are regularly trimmed to keep their shape.
Transplanting
It’s not recommended to transplant mature eucalypts as the roots are quite delicate and don’t like being moved about. Instead, take cuttings or grow new plants from seed.
If you’re transplanting a small tree you purchased from a nursery, dig a hole slightly wider than the container and just as deep. Remove the tree from its nursery pot and place it in the hole at the crown level. Backfill with soil, and pat as you fill to remove air pockets. Then, mulch around the base of the tree, avoiding laying mulch against the trunk.
Growing from cuttings
In summer, take eucalyptus cuttings, dip in rooting powder, plant, keep warm, and water until rooted.
Cuttings can be taken in the summer. Cut a branch about five inches long, dip the cut end in hormone rooting powder, and plant in a pot filled with growing medium or sand.
Keep the cutting warm out of direct sunlight and well-watered until roots have formed, which you will know by gently giving the plant a little tug after about a month.
Growing from seed
Stratify eucalyptus seeds in moist sand for 6-8 weeks, then plant in warm, damp soil for visible germination in 4-6 weeks.
Eucalyptus seeds need to be helped along the way to germination, and the way to do this is to cold stratify them. This process involves placing the seeds close together in layers of moist sand, vermiculite, or perlite and keeping them refrigerated for about six to eight weeks. This helps the seeds to germinate by mimicking wintery conditions.
Once the time is up, place them in pots or trays on damp potting or seedling mix and cover lightly. Place in a warm spot out of direct sunlight and water daily. Germination should be visible within four to six weeks.
Growing as Houseplants
Grow eucalypts as houseplants with proper light and container size consideration for their vigor.
It’s possible to grow eucalypts as houseplants as long as you choose the right variety and give them loads of light. Their vigorous nature will also be tempered by the size of the container you plant them in.
Varieties
Grow Silver Dollar Gum, Cider Gum, Lemon-scented Gum, and Alpine Cider Gum indoors with care.
Here are four varieties that you can grow successfully indoors with the right conditions:
- Silver dollar gum – named for the shape of the silver leaves, moderately cold hardy, and easily pruned to keep them in shape.
- Cider gum – fragrant silver-grey leaves that look good enough for a painting. Cold-hardy.
- Lemon-scented gum – long pointy leaves with a slight lemon scent in a light-green color with a copper-colored bark.
- Alpine cider gum – elongated oval-shaped leaves with blue-green hues.
What they need
- Light and plenty of it. At least 6-8 hours a day; south-facing rooms are ideal.
- A temperature of around 65-75°F (18-24°C), preferably a stable temperature that doesn’t fluctuate much and is out of drafts.
- Humidity at around 40%. Their natural habitat is dry.
- Well-draining soil. A mix of potting soil, coconut coir, and perlite in equal qualities is ideal.
- Watering once the soil is around a third dry – usually once a week. Don’t let it sit in the water.
- Feed once a month with liquid plant food.
- Repot if necessary, every two years in spring.
- Houseplant eucalypts can also be pruned to keep their shape and size.
Common problems
Most eucalypts are not cold-hardy, which means that they could get frost damage if severe. Other than that, and the occasional branch dropping off the tree because of its density, they are all but problem-free.
Pests and diseases
Prevent fungal diseases in eucalyptus by avoiding stress to the tree.
Some fungal diseases will cause stem cankers on the trees. These oozing wounds can cause the leaves to turn yellow and drop off, and even branches drop. With this and other fungal diseases, there is not much of a cure, and it is best to be preventative and make sure the trees are not stressed to attract these fungal diseases. If you do have a problem, the wood should be burned, and gardening implements disinfected.
There are also some borers and other pests that may take advantage of damage in the bark, but there is also not much to be done about them. Prune severely and burn the wood. Whiteflies and psyllids can be blasted with water to avert their feeding.
Often eucalyptus leaves are used as insect repellents and are very effective as a mulch around other plants. What I found most amusing is that in Australia, they call gardens that have been mulched with eucalyptus leaves ‘trash’ gardens when in fact, they are protecting their plants well.
FAQ
The oils extracted from the leaves are toxic. Even small amounts ingested can lead to symptoms that include dizziness and convulsion, and it can be fatal. Rather avoid the oils or try to extract oils from your plants. Just adding branches to a flower arrangement will obviously not be harmful.
The high oil content in the leaves makes them very flammable, and they can burn very quickly. In the native forests in Australia, with the many bushfires that occur, the trees have adapted to survive the fires. The thick bark protects the inner parts of the tree, and those solid-looking gum nuts protect the seeds. However, a tree planted in a garden is unlikely to be a problem and will not spontaneously combust.
As the bark starts shedding, they are very messy, leaving all their bits on the ground around the tree.
Final Thoughts
Eucalyptus have such a wonderful look, and the fragrance is fresh and inviting. They are also fast-growing so that the ‘tree’ look isn’t a long wait. Seeing them in the wild with so many varieties growing together is also a special sight, and there is always a chance of seeing a koala hugging a tree limb if you look very, very carefully…
