Eucalyptus has unmistakably scented foliage and of course, it’s loved by koalas, but will it grow in your garden? What exactly is the difference between eucalyptus globulus vs. radiata? Let’s find out more.
The Main Differences Between Eucalyptus Globulus and Radiata
Eucalyptus globulus and radiata are both tall evergreen trees that can top 100 feet in height, but they have a few differences between them.
The main difference is their foliage. Globulus has much larger leaves that mature to 11 inches in length whereas radiata’s foliage reaches a mature four inches. Another difference is radiata’s foliage has a touch of peppermint, but globulus has the traditional eucalyptus scent.
As well as the foliage there’s a slight difference in their bark too. Radiata has fine, gray peeling bark on a brown-gray trunk, whereas globulus has ribbons of brown peeling bark on a white-cream trunk.
|Eucalyptus globulus||Eucalyptus radiata|
|Foliage||Green. Paler beneath up to 11 inches by two inches||Green. Paler beneath up to four inches by one inch|
|Flowers||Small and white||Small and white|
|Growing Zone||8b and above||8b and above|
|Toxicity||Toxic to pets||Toxic to pets|
|Evergreen or Deciduous||Evergreen||Evergreen|
|Scent||Scented foliage||Peppermint-scented foliage|
What Is Eucalyptus?
Eucalyptus is a flowering tree in the Myrtaceae family. The eucalyptus genus has more than 700 species and many more cultivars bred by botanists to suit gardens and boost their essential oil output.
Eucalyptus globulus and radiata are both species eucalyptus, not cultivars. They both grow wild and were discovered by Europeans hundreds of years ago.
History of Eucalyptus
In Argentina, eucalyptus fossils were found dating back to the Eocene era 51 million years ago and in New Zealand fossils date to the Miocene era, so we know eucalyptus is a very old species of plant. Eucalyptus doesn’t grow natively in these locations now, and some experts think that’s to do with human activity such as Aboriginal fire clearance.
An interesting fact about eucalyptus is that it’s flammable and one of the reasons Australia has such tremendous forest fires. In fact, eucalyptus species are adapted to fire, some even have seeds that are fireproof! Eucalyptus tree on fire have been known to explode due to their high essential oil content.
When Europeans arrived in Australia eucalyptus was formally named by Charles L’Heriter de Brutelle in 1789. Its name is ancient Greek en, which means good or beautiful, and kalypto which means to conceal. Concealment refers to its covered flower buds.
Is Eucalyptus Native to Australia?
Eucalyptus is native to Australia and experts think ¾ of their forests are eucalyptus forests. There are some species of eucalypts native to New Guinea, Indonesia, and the Philippines. Outside Australia, it’s grown commercially for its essential oils.
Globulus is better known as southern blue gum. It was first described in 1800 and in the 1960s it became the floral emblem of Tasmania. Globulus is native to southeastern Australia and it has four sub-species growing in different areas.
- Tasmanian blue gum
- Victorian blue gum
- Victorian eurabbie
- Maiden’s gum
Eucalyptus radiata is better known as narrow leaved-peppermint. It’s native to southeastern Australia and prefers cooler, wetter environments. It was first described in 1828, almost 30 years later than globulus.
Radiata has two subspecies:
- Eucalyptus radiata subsp. Radiata
- Eucalyptus radiata subsp. Robertsonii
Eucalyptus Globulus vs. Radiata: Foliage
The majority of eucalyptus are evergreen but a few shed their leaves in tropical zones. Their leaves are very important to the essential oil market and you can make the most of them by rubbing their surface. Each time they’re rubbed, both eucalyptus globulus and radiata give off that unmistakable eucalyptus scent, but radiata has a peppermint tinge, hence its name narrow-leaved peppermint.
Here are the foliage differences:
Eucalyptus globulus is evergreen. It has young white leaves that are waxy on their undersides. They mature to a lance-shaped glossy green that measure 11 inches long and up to 2 inches wide. It’s the most popular eucalyptus tree for commercial extraction of essential oils for medicines, perfumes, pesticides, and therapy. Its oil is more commonly called cineole.
In contrast, radiata has leaves that are also paler beneath but they are almost straight and much shorter at 4 inches long and under 1 inch wide. They also smell like peppermint!
Do Eucalyptus Globulus and Radiata Have Flowers?
Eucalyptus trees are usually grown for their scented foliage and interesting bark, but they have flowers too. Globulus has green buds that mature to white flowers and eventually into woody seed capsules. Radiata has very similar white flowers that are more cup-shaped and they too ripen into woody seed capsules.
Both species attract many different types of pollinators so they are great for wildlife gardens.
Beware of mixing up their flowering times! Some species are sold as October to January flowerers, but these are the warm months in Australia. In the States, eucalyptus trees flower in springtime
Height And Spread of Eucalyptus Globulus vs. Radiata
In the wilds, eucalyptus ranges from tall trees up to 200 feet to small coastal shrubs only three feet in height. The smaller shrubs tend to grow in extreme environments such as the coast, mountainous regions, and high temperatures. Eucalyptus regnans is the tallest flowering plant on earth. There’s one in Tasmania called Centurion that’s 330 feet tall!
Eucalyptus globulus and radiata can reach 150 feet in the wild, but tend to be much smaller in a garden, plus you can prune them to manage their height. That said, they will still reach 40-50 feet tall even on sandy soil. They make excellent privacy trees if you have multistorey neighbors!
Why Does Eucalyptus Grow So Fast?
They’re one of the fastest-growing trees because in their native environment they have to grow as quickly as possible to avoid koala and kangaroo damage. They tend to grow upwards as quickly as possible to reach the light and put distance between their foliage and predators! As a result, both globulus and radiata are capable of putting on several feet in growth each year, especially if they have rich, fertile soil.
Another interesting fact is that most of their roots only use the top 15-16 inches of soil, so they are very shallowly rooted. This is because they grow in poor, stony soils where it’s often dry. Shallow roots mean they can quickly absorb any rainfall. Unfortunately, this means they are prone to fall in very strong winds.
Eucalyptus Globulus vs. Radiata: Growing Zones
These are both trees that like warmth and they are not frost-tolerant. Both globulus and radiata are best grown in full sun in Zones 8b and above.
If you need a eucalyptus for shade try the species that natively grow beneath the tree canopy such as eucalyptus neglecta or crenulata.
Eucalyptus Globulus vs. Radiata: Bark
Eucalyptus trees have interesting bark that adds a layer each year and sheds its top layer. This leads to rough texture, peeling strips, and other tactile flakes that add interest to the tree.
Globulus has a white to cream-colored trunk with brown ribbons of shedding bark. Commercially it’s a very popular hardwood.
Radiata also has rough peeling bark but it’s very fine and fibrous and its trunk is gray. It’s thin branches are usually gray too and take a few years to thicken up before they start to peel.
Is Eucalyptus Toxic To Pets?
Eucalyptus is toxic to pets, including dogs, cats, and horses. It’s because their leaves and bark contain so much essential oil. Symptoms of eucalyptus poisoning are dribbling, vomiting, diarrhea, and weakness. If you suspect your pet has eaten eucalyptus take them to a veterinarian immediately.
Which Is Best Eucalyptus? Globulus vs. Radiata
It’s difficult to choose between these two evergreen eucalyptus trees. They both reach over 100 feet without intervention and they both have green foliage with peeling bark that’s toxic to pets. The main difference is their foliage.
Globulus has 11-inch long leaves with a traditional eucalyptus scent but radiata has four-inch leaves with a peppermint edge.
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- ASPCA, Available here: https://www.aspca.org/pet-care/animal-poison-control/toxic-and-non-toxic-plants/eucalyptus
- Specialty Trees, Available here: https://www.specialitytrees.com.au/trees/eucalyptus-radiata-5izxq
- The Royal Horticultural Society , Available here: https://www.rhs.org.uk/plants/25081/eucalyptus-globulus/details