🌳 Olive tree

The olive tree is an evergreen tree whose fruit gives olive oil and table olives. In the wild it can reach 20 metres, but in orchards it is kept low so that the harvest is easy to pick. The leaves are narrow and leathery: grey-green on top and silvery underneath from tiny scales, which is why an olive grove seems to shimmer in the wind.

In spring the tree is covered with clusters of small, white, fragrant flowers. They are pollinated by the wind, and a good crop usually needs pollen from another tree, because most olives set fruit poorly with their own. Even so, only 1–5 % of the flowers turn into fruit.

The olive loves warm, dry summers, but it cannot do without winter. To form flower buds it needs six to eleven weeks of cool weather below 9 °C. A mature tree survives winter frosts down to −8 to −12 °C, while late spring frosts and heat above 30 °C during flowering damage the crop. It grows on light, deep soils where water does not stand.

The olive tends to bear a big crop every other year: after a generous harvest the tree grows fewer new shoots, and those shoots are where next year's fruit would form. New trees are raised from cuttings, and the first flowers appear in the third to seventh year. An orchard pays its way for about half a century, while single trees live for hundreds of years.

People domesticated the olive in the eastern Mediterranean or the Middle East; traces of its cultivation go back to the 4th millennium BC. Later the Phoenicians and Greeks carried it along the shores of the whole sea. Today 97 % of the world's roughly 850 million olive trees grow there. Even the wood is valued: it is very heavy and hard, and is turned into bowls and made into furniture and floors.