General Olive Tree Information
Olive trees are very hardy, drought-, disease- and fire-resistant, and can live for a very long time. Its root system is very robust and capable of regenerating the tree even if the above-ground structure is destroyed. The older an olive tree is, the broader and more gnarled its trunk appears. Many olive trees in the groves around the Mediterranean are said to be several centuries old, and in some cases this has been verified scientifically.
The olive is an evergreen tree growing to 25 to 30 ft in height with a spread of about 25 ft. The tree can be kept to about 20 ft. with regular pruning. The graceful, billowing appearance of the olive tree can be rather attractive. In an all-green garden its grayish foliage serves as an interesting accent. The attractive, gnarled branching pattern is also quite distinctive. Olives are long-lived with a life expectancy of 500 years. The trees are also tenacious, easily sprouting back even when chopped to the ground.
The olive's feather-shaped leaves grow opposite one another. Their skin is rich in tannin, giving the mature leaf its gray-green appearance. The leaves are replaced every two or three years, leaf-fall usually occurring at the same time new growth appears in the spring.
"Manzanillo" or "Manzanilla", a medium-large, rounded-oval fruit, with purple-green skin that changes to deep blue-black when mature, originated in Dos Hermanas, Seville, in southern Spain. "Manzanillas" means little apples in Spanish. Known for a rich taste and thick pulp, it is a prolific bearer, grown around the world. The pulp parts readily with its bitterness and is exceedingly rich when pickled. Excellent for oil and pickles.
Olives withstand heavy pruning. Thinning each year shows off branch pattern and eliminates some flowering and fruiting wood, reducing the fruit crop; which can be nuisance in decorative landscaping. Proper pruning is important for the olive. Pruning both regulates production and shapes the tree for easier harvest. The trees can withstand radical pruning, so it is relatively easy to keep them at a desired height. The problem of alternate bearing can also be avoided with careful pruning every year. It should be kept in mind that the olive never bears fruit in the same place twice, and usually bears on the previous year's growth. For a single trunk, prune suckers and any branches growing below the point where branching is desired. For the gnarled effect of several trunks, stake out basal suckers and lower branches at the desired angle.
Prune flowering branches in early summer to prevent olives from forming.
Soil and Growth
Olive trees show a marked preference for calcareous soils, flourishing best on limestone slopes and crags, and coastal climate conditions. They grow in any light soil, even on clay if well drained, but in rich soils they are predisposed to disease and produce poorer oil than in poorer soil.
Olives like hot weather, and temperatures below −10 °C (14.0 °F) may injure even a mature tree. They tolerate drought well, thanks to their sturdy and extensive root system. Olive trees can live exceptionally long, up to several centuries, and can remain productive for as long, if they are pruned correctly and regularly.
Olives grow very slowly, and over many years the trunk can attain a considerable diameter. A. P. de Candolle recorded one exceeding 10 metres (33 ft) in girth. The trees rarely exceed 15 metres (49 ft) in height, and are generally confined to much more limited dimensions by frequent pruning. The yellow or light greenish-brown wood is often finely veined with a darker tint; being very hard and close-grained, it is valued by woodworkers.