A member of the Olive family (Oleaceae), the Olea genus contains about 40 species, the most important being the commercially grown olive. Olea europaea has hundreds of cultivars and is grown around the world.

Form: A single or multi-trunked large shrub or small tree.

Lifespan: 300-600 years.

Leaf retention: Evergreen.

Growth rate: Slow to moderate.

Mature Size: 30' high and wide.

Flowers: Small, clustered, creamy-white. The pollen causes severe allergies. Fruitless varieties produce less pollen and little or no fruit.

Bloom: Spring. Olive trees tend toward alternate blooming, producing fruit heavily one year and lightly, or not at all, the next.

Self-fruitful: Depends on cultivar. Olives are wind pollinated and all trees do better with a second cultivar. Bees are seldom involved.

Years before fruiting: 2-4.

Fruit: A fleshy, oil-bearing, bitter fruit, called an olive, with a thin skin and a single hard pit containing a seed. Green table olives are picked when green and unripe. Dark colored olives are picked when ripe and can be many colors, including red, purple and black. The taste of table olives and olive oil is determined as much by the processing operation after harvest as by the cultivar.

Months for fruit to ripen: 6-8. Olives are mature when they reach their full color. At this time they are ready to drop from the tree. Depending on the cultivar, olives are picked unripe and green for eating or fully ripe for eating or oil.

Storage after harvest: Olives must be processed quickly after harvest, into oil or table olives, to maintain quality. Table olives must be cured, a process that removes bitterness, before becoming palatable.
Curing methods are Brine Curing: fermenting in salt water for up to one year;
Water Curing: each olive is cracked and soaked in daily changes of water for a week or more, then placed in a finish brine with salt and other flavoring elements;
Dry Curing: packing in salt for a month or more;
Lye Curing: using 100% sodium hydroxide with no additives, a method that takes a few days and makes the olives relatively sweet; and
Sun/Air Curing: when the fruit is left on the tree to cure, or picked and left to bask in the sun.
Once cured, olives are sometimes pitted and dried like raisins.
While traditional curing methods often add vinegar to make the olives sour, sugar can be used instead as a sweetener.
Modern olive oil extraction is a complex process that involves crushing the clean olives (and their pits) to a fine paste, mixing (malaxing) the paste for 20-45 minutes to allow tiny oil droplets to combine into larger ones, adding water, and using centrifuges to separate oil from paste. Quality is maintained by not exposing the olives to temperatures over 80°F, light or oxygen during the process and by thorough cleaning of the equipment between each step.

Leaves: Lance-shaped, narrow, to 3" long, thick, gray-green on top, lighter underneath. This tree provides dense shade.

Stems: No thorns. The trunk is gray, bumpy, contorted, and gnarled.

Roots: The extensive root system includes surface roots that can heave walkways and trip pedestrians.

Cultivars of Note for hot desert regions:

Wildlife: The fruit attracts birds. Rabbits may eat the bark, especially on young trees, and greatly harm the tree.

Toxic / Danger: Olive fruit are very bitter, and must be cured to be palatable. However, no part of the olive tree is actually poisonous to animals or humans. The abundant pollen can be a problem for sensitive individuals.

Origin: Eastern Mediterranean. Commercial cultivation began more than 5000 years ago.