Here's a tree with a history almost as long as the history of Western civilization. The olive tree (Olea europaea L.) is native to the Mediterranean, and it has been cultivated for more than 8,000 years. Whether grown for shade or for the tasty olive fruit, also used to make olive oil, these trees are prized and admired by gardeners. The most important aspect of growing olive trees is climate.
Olives are evergreens that can grow to 50 feet tall and 30 feet wide. The tree's billowing canopy has a dignified grace, and the gray-green feather-shaped foliage on gnarled branches also draws the eye. Olives are tough and resilient, sprouting back when chopped down. They can live for five centuries or more.
The small, ivory olive flowers are fragrant. When pollinated, they produce green drupes that ripen into olives. Olives vary considerably in size, shape, flavor and oil content, depending on cultivar. The trees reach bearing age in about four years. You can grow them from cuttings or from seeds.
Many olive cultivars exist. A few are particularly popular in the U.S.:
- 'Arbequina' comes from Spain and has good cold hardiness. It grows to 15 feet tall, is self-fertile and has small, sweet fruit.
- 'Arbosana' also comes from Spain and has moderate cold tolerance. It grows to 15 feet and is pollinated by Arbequina.
- 'Frantoio' comes from Italy and has low cold tolerance. It is self fertile and used for olive oil. The trees can grow to 20 feet tall.
- 'Manzanilla' is from Spain. It produces table olives or oil when it has a pollinator.
- 'Mission' comes from the U.S. and has good tolerance to cold. It is self fruitful and stays under 20 feet.
- 'Pendolino' is grown as a pollinator for Manzanilla. It comes from Italy and has moderate cold tolerance. Trees can grow taller than 20 feet.
- 'Picual' comes from Spain, where it is the top variety planted for oil. It has moderate cold tolerance. Its fruit is pungent and large.
Warm Regions Only Need Apply
Olive trees thrive in U.S. Department of Agriculture plant hardiness zones 10 and 11, while a few hardier varieties tolerate zones 8 and 9. But that doesn't mean all of the states with these zones can be olive territory. Olive trees need a warm climate, but a warm climate alone is not sufficient for olive growing. These trees require a long, hot growing season to properly ripen the fruit. They cannot grow fruit in areas with late spring frosts, since these will kill the blossoms. On the other hand, the winter temperatures have to dip low enough to ensure fruit set.
Almost all commercial olive production in this country is found in California's Central Valley. However, backyard olive orchards fruit satisfactorily in the warmer coastal valleys of California. The tree can also be grown as an ornamental in regions where conditions are not right for fruit production.
Caring for Olive Trees
Olive trees require sunshine. Plant them in full sun without concern about the wind, because they are wind-tolerant. These trees accept almost any well-drained soil and saline conditions. The most important element of olive tree care is water. Irrigation is essential in regions with dry summers, although one monthly deep watering may be sufficient. Feed the trees with nitrogen fertilizer before flower development. Organic fertilizers are preferable.
Regular pruning accomplishes several tasks. It regulates fruit production and also prepares the tree for harvest. You can also prune the tree back radically if you need to keep it at a particular height. Keep in mind that the olive tree bears fruit on the prior year's growth.
If your tree has one trunk, trim out suckers and any low branches. If you have several trunks and want a gnarled look, stake out basal suckers and lower branches to angles that you desire. If you want to prevent olives from forming, trim out flowering branches in early summer.
From Alaska to California, from France's Basque Country to Mexico's Pacific Coast, Teo Spengler has dug the soil, planted seeds and helped trees, flowers and veggies thrive. A professional writer and consummate gardener, Spengler has written about home and garden for Gardening Know How, San Francisco Chronicle, Gardening Guide and Go Banking Rates. She earned a BA from U.C. Santa Cruz, a law degree from U.C. Berkeley's Boalt Hall, and an MA and MFA from San Francisco State. She currently divides her life between San Francisco and southwestern France.