The tallest flowering plant on earth is one of the most desired evergreen tree species for landscaping, the eucalyptus is a fast-growing, insect repelling, and attractive tree that adds beauty and practicality to its surroundings.
When you hear “eucalyptus tree,” a common image is that of a koala bear high up on a limb munching away on the tree’s foliage. Interestingly enough, there are only a handful of animals and insects able to consume parts of the eucalyptus. In large quantities, the chemicals produced by the tree are toxic.
In this article, plantsandtreespecies.wordpress.com will highlight helpful facts, details, and care tips for the eucalyptus tree.
The Eucalyptus in History
Fossilized remains in South America date the eucalyptus tree as far back as 50 million years ago. But it was the arrival of humans some 50,000 years ago on the Australian continent that increased the number of wildfires. The fire-loving eucalyptus flourished and came to account for nearly three-quarters of Australian forests.
It was in 1770 that the first botanical collections of eucalyptus were made by Captain James Cook, Joseph Banks, and Daniel Solander at Botany Bay.
In 1777, it was Cook’s third expedition when David Nelson collected a specimen from Tasmania. It was this specimen which was named Eucalyptus obliqua by the French botanist L’Heritier.
Tree Specifications for the Eucalyptus
Tree Name – Eucalyptus or Eucalypts
Scientific Name/Species – Eucalyptus globulous (there are over 600 documented species)
Family – Myrtle
Genus – Eucalyptus
Nickname(s) – Apple, Ash, Blackbutt, Bloodwood, Blue Gum, Box, Ironbark, Mallee, Peppermint, Ribbon Gum, Scribbly Gum, Stringybark
Lifespan – From 200 to 250 years in the wild.
Type – Evergreen (a small number of the various species are deciduous)
Hardiness Zone(s) – from 7 to 11
Soil Requirements – Eucalyptus trees grow in a wide variety of soil conditions. However, deep, fertile, and well-drained moist soil will provide the best growing conditions.
Planting Spacing – Roughly 20 feet between specimens.
Watering Requirements – Regular when planted. Minimal after 2 years.
Height – Depending on the species, smaller specimens can reach 30-35 feet while larger specimens can tower over 200 feet.
DBH – (Ranges among the species) 8-12ft for many, while some reach over 20ft in diameter at breast height.
Crown Span – 30-80ft or more at maturity.
Root Spread – Wide (30-40ft from trunk) and shallow with 90% of the roots being in the top 12 inches of soil. The tree’s taproot will grow to depths of 6 feet or more.
Uses in Landscaping – Most notably, eucalyptus trees are excellent at slowing or absorbing water in overly wet land.
City or State tree – The Tasmanian Blue Gum (E. globulus), is the floral emblem of Tasmania, Australia.
Folklore, Tradition, and Stories – Long before this tree became a popular landscape addition, ancient aboriginal folk medicine used eucalyptus to heal wounds and treat infections. Eucalyptus oil is one of the most treasured essential oils and is widely used as a decongestant and disinfectant. It can be found in an array of products from air fresheners to toothpaste.
Winter/Fall Colors – Cold hardy eucalyptus foliage can display deep shades of red and purple.
Pests – Termites and some beetles
Major Pest Threat – If a eucalyptus tree is stressed enough, the eucalyptus longhorn borer can successfully attack the tree. The female of this species lays eggs on stressed trees, producing larvae that burrow to the cambium layer. A heavily infested tree can die within weeks, due to the larval galleries girdling the tree and disrupting the flow of water and vital nutrients.
Fungi/Disease – Cankers, heart rot, leaf spot, powdery mildew, and eucalyptus rust.
Major Disease Threat – Eucalyptus rust. This disease is closely related to myrtle rust and belongs to the Puccinia psidii species. Eucalyptus rust is considered to be one of the most serious threats to Australia’s eucalyptus production forests and natural ecosystems.
Level of required care – Minimal.
Eucalyptus Rust Symptoms and Control
Healthy eucalyptus trees are highly resistant to disease threats. However, when this species is stressed by freeze injury, or extended periods of drought, eucalyptus rust can successfully attack younger specimens.
Eucalyptus rust will attack the fruit, shoots, and young leaves of the Myrtaceae species.
Symptoms of eucalyptus rust are:
• Raised pustules on infected tissue, eventually turning yellow.
• Deformed leaves which eventually shrivel.
• Heavy defoliation.
• Stunted growth.
• Repeated infections can result in the death of the tree.
Control of eucalyptus rust is accomplished by:
Prevention through tree Health – Keep your eucalyptus trees in good health by:
• Choosing a proper planting location allowing for unrestricted growth.
• Planting in moist and well-drained soil.
• Deep watering during periods of drought.
Control when eucalyptus rust is detected – Take action by:
• Applying fungicide to affected specimens.
• Carefully pruning affected portions of the tree.
This fungus is easily spread. When pruning is used as a method of control, affected parts of the tree should be disposed of (preferably by fire) and all equipment should be sanitized after use.
Eucalyptus Tree Care
As long as a eucalyptus tree is planted within its hardiness zone, in an optimal location, and with the right soil conditions, the species is able to thrive with minimal maintenance.
Pruning is only necessary to remove diseased or damaged branches, and watering methods should be restricted to dripline or methods which avoid overhead or splashing water to prevent rust disease proliferation.
The health and vigor of your eucalyptus trees is their number one defense against insect infestation and disease.