Olives start out green and eventually all turn black as they ripen. Olives that are harvested when they are still green have a peppery, grassy, or more herbaceous flavour while olives that are harvested when they turn have a milder, buttery flavor.
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Olea europaea is a slow-growing evergreen tree, known for its production of edible olives. It grows in a short and squat habit, the silvery green leaves being small and lance-shaped. The trunk is typically gnarled and twisted. Olive trees produce panicles of tiny white flowers, which generally grow on the previous year's wood and lead on to the production of small olive fruits, which are harvested when green or black. Olives are very significant economically for the Meditteranean region but are being threatened by the bacterial Xylella disease that has spread to several countries. Therefore, olive trees should only be purchased from a safe and reliable source. As well as for olive - and olive oil - production, these trees are popular for ornamental purposes in domestic gardens - particularly well suited for coastal and urban settings in the UK (where they rarely fruit). Can be container grown and lightly pruned to control size.
Common problems with Olive
Xylella bacterial disease - in Europe but not UK