Modifications
Olive trees have withstood the test of time, being almost indestructible. Burning the olive tree is one of the only ways to kill it. Even then, any growth left untouched by the fire may be able to grow into a new tree. Many modifications make the olive tree so sturdy.
Amazingly olive trees do best when left alone. In California, it is important that there be irrigation for the trees but other than that they grow better with some tests from the weather. They have survived some of the driest seasons and then have survived wet ones as well. Olive trees also grow in unlikely places allowing them to grow in places other plants cannot. Not only can they survive in nutrient poor places, the leaves and other material that falls from the trees makes the soil more nutrient rich. These places include rocky, mountainous, unproductive land where most other fruit trees are not able to grow.
Most of this is possible due to the root system in Olive trees. When the season is dry, the olive tree grows a large taproot to better reach the water. Also in the roots olive trees have a relationship with fungus called mycorrhizae. This is further explained in RELATIONSHIPS WITH OTHER ORGANISMS.
Whenever an olive tree is cut back, it will sprout from the roots and can grow from small shoots from the original tree. Many times entire orchards will be burnt to the ground and new trees will sprout up from the remaining roots to create a new crop. This allows the olive tree to survive things most plants cannot and to live longer.