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Mediterranean Gold: The Olive

by a Friendly Gardener
Mixed olives

Anyone from the Mediterranean countries of Italy, Morocco, or Spain can most likely tell you about the importance and glory of the olive tree. These three countries together produce approximately 50% of global production and have some of the best and most highly rated olive oils in the world. Although Tunisia, Greece, and Turkey are highly rated as well.

Olives, as you can imagine from the large amount produced in the Mediterranean region, do best in climates that are hot with longer summers, and where humidity tends to be low. There are numerous varieties, and each will produce an olive that varies somewhat in size and shape, as well as flavor.

As olives tend to be on the bitter side, they are usually cured for consumption or pressed to produce the olive oil used for salads and cooking. Olives are harvested either green or black with green olives being harvested before ripening and black olives harvested once ripened. This is the difference in color.


Cultivating Olives

Olive tree

Ideally, you need to live in an area that offers long, hot summers with a low level of humidity. USDA hardy zones 9 and 10 are best. Olive trees will need a bit of chill during the winter to be able to bloom. Winter temperatures are best when measuring between 40° and 50° F.  While the olive tree can tolerate freezing temperatures, some perish when exposed to temps that fall below 12°F.

Olives flourish when located in the full sun and in sandy, loamy soil. They will adapt to almost any soil type but thrive when the soil pH measures between 5.5 and 8.5. They do not do well in locations exposed to winds or breezes or in spots subject to cold air and frosts.


Selecting an Olive Variety

Freshly harvested olives

If you plan on adding olives to your garden or harvest, it’s important to select the type of olive you prefer. Some olives are great for fruit while others perform much better when pressed for oil. Fruity olives will be preserved or pickled.

Contact your nursery or local olive growers’ association to discover which variety of olive trees will do well in your area and climate.


Olives Need Space

Olive trees field

A mature olive tree can grow anywhere from 15 to 30 feet in height and in width, so this is a plant that requires a bit of space. You can prune your olive tree and train it to a more manageable size if necessary or so desired. It is a good practice when positioning your olive tree or trees to place them approximately 20 feet apart or away from other trees.


Olives and Pollination

While most olive trees are self-pollinating, they will have a better chance of flowering and producing fruit if they are pollinated by other nearby olive trees.


Preparing for the Planting of Olive Trees

Olive trees in soil


·         When to Plant

Avoid planting olive trees in the heat. This means it’s better to plant in the springtime or in autumn when temperatures are more agreeable.


·         Selecting a Location

Olive trees love the sun so look for a location that receives full sun. Ideally, the spot should also be sheltered from winds and breezes.


·         Preparing the Soil

Work the soil bed before planting with manure or well-rotted mature compost.


Planting Your Olive Tree

Olives growing on a branch

When preparing a hole to plant your tree in, observe the tree’s roots. The hole you prepare should be 1.5 times the length of roots in depth, and twice the size of the root system in width. Place one cup of all-purpose fertilizer inside the hole before planting.

Place a tree stake at the site before you position your tree. It should be driven into the ground at least two feet deep and positioned at the side of the hole.

Remove any burlap or twine on the tree if it was balled and burlapped at the nursery for transport.

Position the olive tree within the hole in such a way that the nursery pot soil mark is even with the soil surface in your garden. The tree can also be set an inch or two deeper within the hole. Spread out the roots in all directions around your plant.

Green olives growing

Now fill the hole with half of the area’s native soil and half enriched soil. You can use an organic potting mix or mature compost as the enriched soil half. Pat the soil gently to firm it up so that no air pockets remain around the roots. Water the soil well. Create a small indentation or basin at the base of the olive tree to hold water for future waterings.

Secure your olive tree to the tree stake using tree ties. Once you have finished water the tree or trees again thoroughly and add in a starter liquid fertilizer that is high in phosphorous content.


Cultivating Olive Trees in Containers

Indeed, olive trees can be cultivated in containers if you do not have the possibility to plant them in the ground. Select a large pot or container that measures at least 18 inches deep and wide with good drainage.

Plant the tree in good quality organic potting soil. Water sufficiently to keep the soil bed evenly moist but not wet. Fertilize container olives with a liquid fertilizer that is slightly higher in potassium content.

Repot your olive tree every two years in a larger pot. If you began with an 18-inch container, move to a 24-inch container the second year, and so on.


Caring for Olive Trees

Growing olives

Initially, your olive tree will need regular watering until the root system is well established. Mature olive trees tolerate some drought better than young plants. They do need, however, regular watering during the flowering period.

Feed your olive tree once annually with nitrogen fertilizer such as cottonseed meal or blood meal. Do not overfeed your tree or too much fruit will set.


Olive Tree Training

Green olive growing

Olive trees are not best left to their own devices as they can grow to become quite unruly. Olive trees should be trained through pruning.

When you plant the olive tree, trim the central lead by cutting at an angle approximately five feet above the bud. Remove any lateral branches that are below 18 inches in height from the soil surface. Trim all remaining lateral branches by half.

During your tree’s first summer in your garden, prune the principal lateral branches to 8 inches from the year’s new growth. Buds should be cut so that the face is outward. Prune any new shoots to approximately 6 inches in length. Do not prune the central lead.

When the second spring arrives for your olive tree, prune the central lead so that it is approximately one-third of the growth from the preceding year.

During the springs that follow, prune the central lead two-thirds of the preceding year’s growth. Do this every year until your tree reaches your desired height.

Always remove diseased, damaged, or dead wood as well as the growth that is unproductive at the center of the tree. Continue pruning the central lead to approximately one inch or the preceding year’s growth.

Mature trees should be pruned yearly to maintain their shape. Thin out congested branches so that both sun and air can arrive at the tree’s center. Remove any excess fruit manually. For better production limit each twig to 3 or 4 fruits. This will increase fruit size. Once fruits begin to develop, thin as soon as possible.

Lay a thick covering of composted manure at tree bases in autumn. If your area is at risk of freezing, cover trees with blankets or burlap.


Olive Diseases and Pests

Olives are susceptible to

  • Olive knot disease (swellings or galls)
  • Peacock Spot Fungal Disease (typical of excessive rainfall, it appears on foliage)
  • Verticillium Wilt (a fungal disease that begins on foliage)
  • Scale (a waxy sap-sucking pest on stems and leaves)


Harvesting Olives

Olive oil

After you plant your tree, you’ll need four to five years before the fruit appears. Olive crops alternate from year to year. One year you will have a heavy crop, and the second year, a lighter yield. Your olives can be harvested while unripe or green, or when ripe or black. For oil production, olives are harvested when externally black, but still green within.

Harvest your olives manually as these fruits are easily bruised. If you hope for oil production, position netting at the base of the tree and knock or shake branches so that the olives fall to the ground. Gather the nets filled with olives for transport to the press.


Storing and Eating Olives

Olive oil with bread

Green olives can be pickled. They can also be brined and then stored. Olives must be cured before they can be consumed. Olives served at meals are generally prepared with water, brine, oil, or lye to lessen the bitterness and for conservation purposes.

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