Olives have been eaten and their oil used for thousands of years. In the Middle East olives have been cultivated for 6,000 years, and olive oil was an important trade item in the ancient world. Today it is a basic ingredient in healthy Mediterranean-style cooking, with both the oil and the fruits being used. The health benefits of olive oil are widely known and olives and their oil are strongly suggested as an important part of a healthy diet. Olive trees are famous for their resistance to drought and harsh growing conditions and for their longevity. As a garden plant however the Olive Tree is often overlooked, but if you live in a suitable area they are an attractive, easily-grown plant that will also provide a good crop of fruit that can be turned into those tasty delicacies that so many of us enjoy. That way you can enjoy all those health benefits from your own garden, instead of buying commercially produced products.
The Olive Tree is a small evergreen tree growing from 15 to 30 feet tall, depending on the variety. The leaves are small, leathery and a silvery grey-green color. The tree is very drought-resistant and grows at a moderate rate of around one foot a year. In the garden they can be trained as a small tree or as a large bush, and because they are evergreen they make an effective wind-break or screen, particularly in sunny, exposed, dry areas. The grey-green foliage is a great visual addition to the plain green of most other garden plants and can be used very effectively in collections of shrubs and trees. They are great companions for hardy palm trees and other drought-resistant plants to create a low-maintenance low-water garden.
The Olive Tree (Olea europaea) is native to the countries of the Middle East and around the Mediterranean, but it has a long history in America as it was brought to California by the Spanish Missionaries in the late 18th century. It is a small to medium-sized tree 15 to 30 feet tall, although some varieties can reach 50 feet. Most trees in cultivation are kept to 12 or 15 feet by pruning. The tree is broad and rounded, with a thick trunk which is dark-grey and deeply ridged and grooved. In time the trunk becomes twisted and picturesque, adding to the rugged beauty of this tree. The leaves are about up to 4 inches long and an inch wide, but are usually smaller than that. The flowers appear in spring as fluffy white sprays, which are followed by the olives which begins green and pea-like and gradually develops into a purple or black fruit that ripens in the fall.
There are hundreds of varieties of olive trees grown in different regions of the world; most are descendants of ancient local varieties. Most varieties of olive require another variety nearby for cross-pollination, but some, like the Arbequina Olive Tree, are self-pollinating, so such a variety is an ideal choice when you just have room for one tree.
Varieties differ in the flavor of their oils, so for example most traditional Californian varieties like ‘Manzanillo’ and ‘Mission’ produce mild oil, while the Arbequina Olive Tree yields aromatic and fruity oil. For eating, the variety has little impact because most of the flavor development and final taste depends on the method used to prepare the olive for eating. Choose a variety with a relatively large amount of flesh for its overall size for the best eating experience.
Olives are very drought and heat resistant and will grow in zones 8 to 11. However for good fruit production they need cool winters – in warmer areas they will grow well but rarely fruit, so you can certainly enjoy their beauty in Florida or southern Texas, but for fruit production you need to live in areas which are cold enough for the trees to stop growing during the winter. For good fruit development the daily average temperature in mid-winter needs to be below 500F; for example 400F at night and 600F during the day. So for fruiting, zones 8 and 9 are usually best.
On the other hand, olives are not generally tolerant of severe frost. Minus 50F will definitely kill an olive tree, but trees will normally take nights down to 200F with no problem. Gardeners always want to test the boundaries and if you live in zone 7, some of the hardy varieties, like the Arbequina Olive Tree can thrive if given a good location. Hardy varieties will take 150F with little or no damage.
The key to growing olives in colder areas is to use local micro-climates; against a warm south or west-facing wall, in a south-facing sheltered position and on a slope not in a hollow. Of course Olive Trees also make good plants for pots and can then be grown all the way to Alaska. Pots can be brought inside during the cold parts of winter and placed in a well-lit location. For fruiting it will be necessary to store your tree in a cool place over the winter as inside the house will be too warm. During the growing season hot summers are never a problem since olive trees thrive when the temperature is over 850F and don’t even suffer when it hits 1150F. Hot weather actually helps to develop the fruit.
For a single tree, allow 15 feet spread. When planting a grove a number of methods are used. Trees more widely spaced will produce more fruit per tree, but when averaged over an acre closer spacing has a higher yield. So growers may plant from 30 feet apart all the way down to 10 feet apart. For a row that will serve as a screen or windbreak and also as a source of olive, 8 to 10 feet is ideal.
When you are ready to plant your olive trees, begin by digging some organic material like compost or rotted manure into the area and add lime if your soil is acidic. Olives do best in neutral to slightly alkaline soils. Dig a hole two or three times the width of the container, remove the tree from its pot and place in the hole so that it will be at the same depth as it was in the pot. Replace most of the soil, water very thoroughly and when the water has drained away completely, fill in with the rest of the soil. Water once a week for the first growing season and after that additional watering will rarely if ever be required. When young your trees will benefit from water during extended drought periods.
Watering is rarely needed for olive trees, but for a good harvest they do need water during the winter months. So if you live in an area with low winter rainfall, soak your tree at least twice during the winter. Pruning olives is generally simple as the main goal is to keep the tree open enough for light to penetrate and ripen the fruit. A vase shape with several branches coming out at an angle and an open center to the tree is the usual form used. Low branches and any broken ones should be removed. Any significant pruning should be done shortly after harvesting and remember that olives make their fruit towards the end of shoots formed the previous year, so shearing back like a hedge will reduce the yield. Fertilizer is not normally needed, but an annual mulch of compost or manure applied each winter is beneficial.
Harvesting is done in fall and fruit can be harvested green, half ripe or when black and fully ripe, depending on your taste. For one or a few trees the easiest way to harvest is to place sheets beneath the trees and use a metal rake to pull the fruit from the trees. Fresh olives are too bitter to eat so they are soaked in several changes of water until enough of the bitterness has been removed. They are then preserved in a salt brine, with or without vinegar and flavorings and then stored in oil that can also be flavored with herbs, chili or other flavorings. The preparation process can take several weeks, but the work is very easy and most of the time the olives need no particular attention. Thinking about how great it will be to eat olives from your own garden will make the time go quickly.
Making your own oil needs some equipment, but if you have several trees it could be a worthwhile activity as it is not difficult and the result will be premium extra-virgin oil that is sold at boutique stores for very high prices.
It doesn’t matter if you grow Olive Trees for their beauty, toughness and drought resistance or to produce your own eating olives or even extra-virgin olive oil – an olive is a tree that should be in every garden warm enough to grow one. Even if you live in a cooler region, an olive tree in a pot will look great on your terrace and be a terrific conversation piece with your friends. When you then pass the bowl of olives, they will be amazed!