🌳 Olive tree

The olive tree (Olea europaea) 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. Its narrow, leathery leaves live 2–3 years: grey-green on top and silvery underneath from tiny scales, so a grove seems to shimmer in the wind.

In spring it produces clusters of small, white, fragrant flowers. They are pollinated by the wind, and most cultivars need pollen from another tree. Only 1–5 % of the flowers become fruit; the fruit, a drupe, grows for 6.5–7 months and builds up its oil in the last 20–40 days. After a heavy crop the tree grows fewer new shoots, so the olive bears unevenly, with good and poor years alternating.

The olive loves dry, warm summers but cannot do without winter: to form flower buds it needs 6–11 weeks of cool weather below 9 °C. A mature tree survives winter frosts down to −8…−12 °C, but spring frosts and heat above 30 °C during flowering damage the crop. Olives are grown between 30° and 45° latitude in both hemispheres; there are over 11 million hectares of olives in the world, and of roughly 850 million trees, 97 % grow in the Mediterranean.

The olive is one of the longest-lived crops. An orchard stays profitable for about 50 years, and individual trees live for centuries or even millennia; many old olives are grafted onto rootstocks of the wild olive, the oleaster. The olive was domesticated in the Eastern Mediterranean about 6,000 years ago, probably in the lands between present-day Syria and Turkey.

Why it matters to you. Want to grow an olive at home? Without a cool winter it will not flower. A seedling grown from a stone will flower only after 4–9 years and will not reproduce the cultivar. That is why olives are propagated from cuttings: a rooted cutting flowers 3–7 years after planting.