The Eucalyptus are a genus of over several hundred species of flowering trees, shrubs or mallees in the myrtle family, Myrtaceae. Together with several other genera in the tribe Eucalypteae, including Corymbia, they are commonly known as eucalypts.

All eucalypts are not Eucalpytus, as the term ‘eucalpyt’ refers to three closely-related genera of the family Myrtaceae – that includes Eucalyptus (approximately 758 species), Corymbia (approximately 93 species) and Angophora (approximately 10 species). All together, they are colloquially commonly called ‘gum trees’.

Eucalypt Discover Walk, Australian National Botanic Gardens,

Most eucalypts are native to Australia, with three-quarters of Australian forests being eucalypt forests (although with continual land clearance this is changing). Whilst most eucalypt species are adapted to fire (re-sprouting after the fire and seeds that can survive fire), it is highly likely that with the high-intensity fires of recent times and repeated fires, this environmental and climatic change may prove a challenge for the natural regeneration of eucalypts.

The genus Eucalyptus have bark that can be smooth, fibrous, hard or stringy. The leaves have oil glands that can often be smelt as you approach or stand near the tree, especially on warm days or within a eucalypt forest.

The Blue Mountains of New South Wales, when viewed from a distance appears to have a blue haze blanket the region. The region is densely covered with eucalyptus and gum trees growing in the area (there being four main types of eucalyptus trees that cover the regions hills, mountains, canyons, valleys and plateaus). As a consequence, the eucalyptus forests in this region emit huge amount of oils into the atmosphere. It is thought, that the eucalyptus oils, dust particles, and water vapour combine, and as the sunlight hits this atmosphere, it creates an optical illusion of a blue haze. The light allowing the eyes to see the blue pigments in the atmosphere. However, there is another theory

the sky is blue because tiny air molecules of oxygen and nitrogen, water molecules, and dust motes interact with light. The small size of these particles means that high-frequency light (like, blue) is much more likely to interact than low-frequency light (such as red). The interaction scatters blue light in all directions. Consequently, we are more likely to see blue light than any other colour. Thus, the sky looks blue.

Consequently, distant dark mountains reflect little light to our eyes. Our eyes receive much more light from sunlight scattered by tiny molecules between us and the mountain. That scattered sunlight is blue. So, it isn’t a scattering of light reflected from the mountain that makes the mountain appear blue, but rather a scattering of light between us and the mountain. (WeatherQuesting Web Site)

Blue Mountains Association of Cultural Heritage Organisations
View of Mount Solitary from Echo Point, Blue Mountains
View across forests of mainly eucalypts to Mount Solitary from Echo Point, Blue Mountains

The sepals and petals of Eucalyptus are fused to form a ‘cap’ or operculum over the stamens. The fruit is a woody capsule that is commonly referred to as a ‘gumnut’.

Red-Bud Mallee (Eucalyptus pachyphylla), Olive Pink Botanic Garden
Red-Bud Mallee (Eucalyptus pachyphylla), Olive Pink Botanic Garden

  • Scientific classification
  • Kingdom: Plantae
  • Clade: Tracheophytes
  • Clade: Angiosperms
  • Clade: Eudicots
  • Clade: Rosids
  • Order: Myrtales
  • Family: Myrtaceae
  • Subfamily: Myrtoideae
  • Tribe: Eucalypteae
  • Genus: Eucalyptus
  • Species: there are over 700 Eucalyptus species

Footnote & References

  1. Eucalyptus, (last visited Jan. 2, 2021).
  2. Why Australia’s Severe Bushfires May Be Bad News For Tree Regeneration, by Associate Professor Lauren Bennett, Dr Sabine Kasel, Dr Tom Fairman, Ruizhu Jiang, University of Melbourne. This article was first published on Pursuit. Read the original article.
  3. Eucalypts and Fire – Forest Education Foundation,
  4. Why are the Blue Mountains blue? Blue Mountains Association of Cultural Heritage Organisations,