Days to germination: Started as seedlings or grafted cuttings
Days to harvest: 3 to 4 years of age
Light requirements: Full sun
Water requirements: Occasionally
Soil: Sandy soils with great drainage
Container: Possible with smaller varieties
Olives are grown on trees that only thrive in hot tropical regions, and in the United States that means only in zones 9 to 11. Some sheltered parts of zone 8 may be suitable as well.
Some types of olives are bred for their oil production, and some are intended to be eaten (table olives). Many can easily be used for either purpose, but some should be left to their intended use. Manzanillo and Kalamata are popular for table fruit, whereas Koroneiki and Pendolino are typically just oil olives.
Fresh olives off the tree are quite bitter, and they are usually brined, pickled or cured for eating. You can get either green or black olives from any tree, it just depends on when you pick them.
For a fruit, olives are quite high in fat though the qualities of olive oil are typically healthier than many other kinds of fats. They are also great sources of iron, vitamin E, fiber and even copper.
Starting Your Tree
Any location that will get full sun and has well-drained soil is perfect for an olive tree. Sandy soils are fine, but any loose type of soil would do. Lower areas may provide more protection from frost, but you can also end up with water accumulation in low spots which will quickly kill your tree. A gentle slope can make a big difference in keeping good drainage.
Whether you need more than 1 tree will depend on the cultivar you are growing. Some kinds of olive trees will fruit on their own (they are self-fertile) and some will require at least one additional tree. Arbequina and Frantoio are both self-fertile, for example but Manzanillo and Leccino will need another tree to pollinate. Check at your nursery before purchasing, so you have have a single lovely tree that never gives any olives.
Olive trees have very shallow roots, so you won’t want to do any digging or deep cultivating around your trees even after they have matured. Olives can handle dry weather quite well, but if you keep them watered they will produce better fruit. Give them a soaking once a week if there hasn’t been any rainfall.
Pruning is important with an olive tree, to keep the size convenient for harvest. If you are not familiar with pruning techniques, you should ask at the nursery for some tips when you buy your tree. But even a novice pruner can handle a few strategic cuts each season to improve the olive harvest. Remove any dead branches, and also trim out any branches that cross one another. Also prune out some of the central (but not the main) branches to let more light into the middle of the tree.
A yearly feeding with standard mixtures of fertilizer are very helpful, usually applied before the trees go to flower.
Because of the shallow roots, olives trees are particularly well suited for container gardening. You will need to choose a dwarf variety though, such as Arbequina and Picholine. Arbequina is also a good choice in cooler areas, as it can still fruit up to zone 7.
Your pot should be at least 2 feet across and 2 feet deep. Using sandy soil that drains well so that your tree doesn’t have to sit with wet roots. Let the soil get dry at least an inch deep between waterings, and keep your tree in the sun.
A container tree will need more pruning than a garden tree, so keep your olive tree down to 3 or 4 main central branches and don’t let the tree get too tall either.
Pests and Diseases
Black scale and damage your olive trees when present in large numbers, though a few are generally not too harmful. They look like flat scales on the bark, though they are actually a beetle and they can be treated with the proper insecticide for scale. Healthy trees usually don’t have any problems with scale but the insects excrete a sweet liquid that will attract ants and cause mold on the leaves. So watch not only for the scale themselves but these other symptoms as well.
Verticillium wilt can also attack olive trees (particularly in California), and it causes leaves and branches to suddenly wilt. If you cut away the infected branches, you may be able to keep it from spreading but there is no other treatment for this fungal disease. Some varieties of olives are available in resistant types. Wilt does effect a number of other plants and can survive in the soil for years. If you have had problems with it in the past, do not plant any olives in that area.
Harvest and Storage
Deciding when to harvest your olives depends on whether you are looking for green or black olives. Green olives should be picked when they are still green (obviously) but have reached full size, and they will still be very firm. Otherwise, wait until they turn black for a later harvest of black olives. They will be softer and more prone to bruising at this stage. Typically, your tree will start to develop its fruit between 5 and 7 months after it blossoms.
Most olives will start to fruit after 3 or 4 years, and after that you and your descendants will be picking olives for many generations. These trees can actually live and bear fruit for more than a hundred years.
Since few people actually eat fresh olives, the fruit is usually processed (curing or brining) before you store them. Brining your own olives isn’t really difficult but it can be quite time consuming and usually involves soaking them in salt water. The olives are left to soak for several weeks with the water being changed daily. The full process is too elaborate to outline here but a good Italian cookbook should lay out the steps for you.
Once they are ready to eat, you can store them in their brine solution for several months but that can depend on the method you use to cure or brine them in the first place.