Olive trees are prorogated from cuttings. When the cutting has taken root under special care in the greenhouse, it is ready to be planted in the ground. Depending on the type of olives desired, anywhere from fifty to three hundred trees could be planted per acre. The first fruit will appear after four years, and the trees reach peak production between twelve and fifteen years. Young unripened olives are green with a smooth, tight skin.
Mature olives are black with a wrinkled skin.
Sizes range anywhere from the small Nicoise olive to the plump Kalamata. The flavor of olive oil depends on the time at which the olives are harvested. According to the California Olive Oil Council, green olives picked before maturity produce a rich and fruity oil. The more mature the olive, the more mild the oil flavor, although the amount of actual oil produced upon pressing is much higher than with green olives. The type of olive also adds to the oil's flavor, but most oils tend to be blends of several varieties.