Eucalyptus flowers have no petals, just a lid that pops off
The name eucalyptus means well covered, after the woody cap that seals each flower bud until the swelling stamens shove it off. Behind that little lid sits a genus of more than 700 species, including Eucalyptus regnans, the tallest flowering plant known anywhere on Earth.
Almost all eucalypts are Australian, with representatives in every state and territory, and a few species live on islands to the north. They range from towering single-trunked trees to mallees, which sprout several stems from ground level and seldom top ten metres, to stunted shrubs under a metre tall clinging to Tasmanian highlands or Western Australian sea cliffs. Western Australians even have special words, mallet and marlock, for particular growth forms. Europe's tallest reliably measured tree, a 72.9-metre karri in Portugal, is a eucalypt.
Every year a new layer of bark forms and the outer layer dies. Roughly half the species shed that dead skin in slabs, ribbons or flakes, exposing bright fresh bark; the rest keep it, producing the spongy stringybarks, the hard, furrowed ironbarks soaked in dark resin, and half-barks whose rough lower trunk gives way to smooth limbs. Bark cells of the Tasmanian blue gum can photosynthesise when the leaves are gone, helping the tree recover after fire.
Leaves change dramatically as a plant matures, from opposite, stalkless, bluish seedling leaves to hanging, glossy adult ones, which is why eucalyptus shade is so patchy. Some species keep juvenile foliage for life and are prized as ornamentals. The oil glands dotting every leaf are a defining trait, and the flowers, lacking petals, advertise with masses of fluffy white, yellow, pink or red stamens before ripening into woody gumnuts.
Joseph Banks and Daniel Solander made the first known collections at Botany Bay in 1770. The genus itself was named by the French botanist L'Heritier from a specimen David Nelson gathered on Bruny Island in 1777, during Cook's third voyage. Grown worldwide for timber, pulp, honey and oil, eucalypts have been removed in some countries because they burn so readily.
Source: Eucalyptus
