Eucalyptus

The eucalyptus is a very fast-growing tree that can exceed 30-55 metres in height, reaching even 90 metres in some exceptional specimens in its native Tasmania. Its straight, slender trunk sheds its bark in long strips as it grows, revealing a greyish or bluish tone beneath.

One of its most curious features is heterophylly: young leaves are rounded, opposite and bluish, while adult leaves become elongated, sickle-shaped and a darker green, hanging from the branches in a characteristic way. Its whitish flowers, without showy petals, develop protected by a sort of "lid" (operculum) that falls away when they open, and give rise to woody, capsule-shaped fruits.

It is native to south-eastern Australia and Tasmania, where it grows naturally in coastal areas with a humid, temperate climate. It reached Spain in the mid-19th century, around 1845-1868, probably via Portugal, and became popular as an ornamental species before becoming a major forestry crop.

During the 20th century it was planted on a massive scale in forest reforestation schemes because of its extremely rapid growth, coming to cover hundreds of thousands of hectares in the Iberian Peninsula, especially in areas devoted to the paper industry.

An essential oil rich in eucalyptol is extracted from its leaves and widely used in traditional remedies to relieve respiratory congestion, although in high doses it can be toxic.

Its enormous growth capacity — up to 40 cubic metres of wood per hectare per year — made it the basis of the pulp and paper industry in Spain and Portugal, although its spread also generates debate because of its high water consumption and its behaviour as a pyrophytic species, highly flammable in forest fires.