Everyone knows the olive, a staple of cocktails and great in salads. But have you ever considered growing olives yourself? Perhaps more importantly, is an olive a fruit or a vegetable?
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Most people seem to consider them to be vegetables. But those black olives on tree branches are most definitely a fruit. They develop in a range of colors: purple, green, dark brown, black, and even pink! Both dwarf olive trees and regular ones originated from western Asia and spread down the coast of the Mediterranean Sea.
These lovely trees are evergreen and are considered to be one of the longest-living fruit trees. The average lifespan of these trees is generally between 300 to 600 years. However, some trees can live up to be 4000 years old. One of the oldest olive trees is on the island of Crete. It is believed to be over 4000 years old. The astonishing part is that the tree is still producing fruit!
The fruit is loaded with minerals. They are also rich in Vitamin A, B, E, and K. Almost 20% of the fruit is oil, and that shows in its use. While these fruits are used in the culinary world in multiple ways, olive oil is one of the largest uses. About 3.3 million metric tons of olive oil is produced every year.
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All About Olives
The botanical name of olive is Olea europaea. Generally, the fruit goes by the name olive, and the tree is simply known as the olive tree. The tree generally reaches a height of 8 to 15 meters (26 to 49 feet) with a round and well-branched crown.
The leaves are long and oval in shape. They have a leathery texture and are a dark green color on one side and greyish-green on the other. The tree also produces flowers that eventually become the fruit. The olive flowers are small and white. They generally appear once the tree is established, a few years after planting.
The tree grows quickly in the first few years of its life. However, growth slows down as the tree matures. Various types of these trees are grown in all Mediterranean countries. It is also harvested in Australia, New Zealand, South America, South Africa, and the United States. Some popular types of olive tree include the following list: Arbequina, Mission, Gaeta, Kalamata, Nevadillo Blanco, and Bucida.
The fruit itself comes in a myriad of colors and uses. While all varieties are technically black olive tree types, many popular varieties are harvested early for their less-ripe green fruit. The Manzanilla is one of the most popular green olives in the United States, for instance, and the Arquebina is prized for olive oil production in its fully-ripe black state. If you find the taste not to your liking at a green stage, keep growing and wait for the fruit to fully ripen!
Planting Olive Trees
Olive planting can be a rewarding experience! But knowing when, where, and how to do it is essential. If planted in the wrong location, you may not have as long-lived a tree as you might otherwise, so plan ahead.
Normally most olives are planted in the spring or fall months. Some limited summer planting is possible if the weather is mild, but it is essential that your tree has time to become somewhat established before heat or cold settles in. For best success, early spring planting is ideal.
Select a location that is appropriate to grow olives in. These trees prefer a Mediterranean climate, one that doesn’t get too cold in the winter. In addition, olives grow to be about 20’ in diameter, so spacing can be essential. If you are planning on keeping your tree more compact, you may be able to place trees a bit closer together.
Choose a location that avoids any underground pipes as the roots can break through most types of piping over time. Similarly, place your trees away from fences or walls, and far enough from buildings that the roots cannot cause damage as they develop. Also keep an eye on any suspended cables, so that your tree cannot grow around the wires.
Those who choose to have a multi-trunked tree may be able to maintain it a bit shorter and still have a successful harvest. A single-trunked tree will need to utilize its entire canopy. In the wild, olives often sprout multiple trunks from soil level, creating a bushier-looking plant overall.
How To Plant Olives
Most trees at the local nursery will come in a 1-gallon sized container, with the sapling itself roughly 3-4 feet in height. You will need to dig a hole that matches the size of your container. When you dig a hole, use the blade of your shovel to roughen the sides of the planting hole so that it’s not completely smooth.
Do not amend your planting hole with high-quality potting mixes. This produces a “false pot” effect and can cause the roots to circle in the ground rather than spread its roots out. Instead, plant in your native soil as that’s what the roots will have the most contact with..
Once your hole is dug out, plant the sapling slightly higher than grade and backfill with more native dirt. Aim for about 1” coverage of the root ball. If your area is not windy, try to avoid staking if possible, but in windier areas place stakes on either side of the tree to secure it in place. Water it all in very well.
It is possible to grow olive trees in pots, but you often won’t have as large of a mature plant, and it can easily become rootbound. It may not produce as much fruit as an in-ground tree will.
Care
With proper care, this tree will offer bountiful fruit for years. Let’s go over the ideal conditions to grow olives in and how best to keep them thriving!
Sun and Temperature
Grow olives in full sun conditions, preferably in areas with mild winters and long, dry summers. Aim for at least 8 hours of sunlight daily.
Olives are at risk of frost or freeze damage. Temperatures below 22°F (-5° C) can damage the trees. Temperatures below 15°F (-10° C) are likely to kill the tree. Ideally, these should be grown in USDA growing zones 9-11, but zone 8 can manage to grow olives with some winter protection.
Watering and Humidity
Young saplings have greater watering needs than established trees. For ideal growth, water young plants well at least 2 to 3 times every week during their first summer. Keep the ground moist at the root level for best results.
In the second year and subsequent years, provide extra water during hot weather but you can reduce the watering frequency gradually as their root depth improves. These are good drought-resistant species when mature and are able to handle dry conditions favorably.
Soil
Olives grow best in non-stratified soils with a moderately fine texture. Ideal types to grow olive trees include loamy soil types – sandy loam, clay loam, and silty loam. These provide good aeration for root development and also feature a good water-holding capacity. Better-draining sandier soils are also an option. Try to avoid dense clay soils as they can hold too much moisture and may promote rot conditions in the roots.
A wide range of soil pH is tolerated when growing these – 5.5 to 8.5 pH is fine.
Fertilizing
Do not fertilize your olives between August & March; they don’t need fertilizer during the fall and winter months. For spring and summer, a slow-release balanced fertilizer in the 10-10-10 ratio is appropriate. Apply according to the manufacturer’s directions for the frequency of fertilizing, but keep it away from direct contact with the trunk or roots as it may cause fertilizer burn.
Pruning
If you buy a very young seedling or grow from seed, the seedling may have multiple trunks. It’s best to avoid pruning extra trunks away until the sapling is at least 1 year old. After that point, if you want a single-trunked tree, select the best-looking trunk to keep and trim the others away cleanly.
Pruning should be done before buds set in the early spring. If possible, make sure any pruning wounds have time to dry and scab over before the next rain to reduce the risk of disease transmission. Fruiting occurs on the prior year’s wood, so don’t remove much of the most recent growth or you can impact harvest. Thinning to improve airflow in the canopy is fine. You shouldn’t have to prune heavily that often; a good thinning every two years should be fine.
At all times when pruning, use sterilized loppers or pruning shears. Olives are susceptible to bacterial diseases that can be difficult to treat.
Propagation
Propagation of olives can be performed from seed or cuttings. However, the best-growing olives are often nursery starts as they are healthy and ready to plant.
To start from seed, you will need fresh, ripe green olives harvested directly from a tree. Break the flesh open and soak the olives in water to remove the seed from the flesh. Make a little nick to dent the pointed end of the seed coat with a sharp knife, then soak again for 24 hours in room temperature water. You can then plant it pointy-side up in a seed starting mix at twice the seed size in depth. Please note that seeds may not produce an exact clone of their parent olive trees.
When growing an olive tree from cuttings, select healthy first-year twigs that are about the diameter of a pencil. Remove all but a few leaves at one end, and dip the cut end into rooting hormone before placing into pre-moistened seed starting mix. Caring for cuttings is fairly simple, and while potted olive trees like this can take a while to develop roots, they will eventually be a perfect match to their parent.
Harvesting and Storing
Olive trees can take a while to grow, but the harvest makes it worth it — whether you’re growing for the fruit or for olive oil pressing!
Harvesting
Olive trees may be harvested at any stage through October to December. Well ripened fruit will be black in color, but you can pick at any stage from green through reddish-brown and into black. To gauge the state of the produce, pick a couple of olives and squeeze them. If the juice is cloudy, it can be harvested for processing as its current color.
Well-ripened fruit will fall from the tree with a light shake of the branches. Green fruit may require more vigorous shaking or handpicking. If harvesting for the fruit itself, handpicking is best as the fruit can bruise easily.
The fresh fruit is not actually edible immediately after harvest, although it’s fine for pressing oil at that stage. Olives contain oleuropein, a naturally-occurring chemical that makes the flesh extremely bitter. So let’s talk about curing and storage in more detail!
Storing
The simplest method for most people is to cure your olives in water. Pit or slice the olives to expose the flesh of the fruit, then immerse them in a jar of water with a weight to keep them completely submerged. Add a sliced lemon to the water if desired to slow fruit discoloration, and place the jar in the refrigerator. For the next couple of weeks, replace the water in the jar once to twice a day with fresh, rinsing out the olives. Remove the lemon after the initial soaking.
Once the olives have lost some of their bitterness, place them in a brine and vinegar solution for at least a week. Mix 100g salt with 1 liter of water, heating until the salt completely dissolves, and this will be a safe 10% salt brine to use. 150ml of vinegar plus your liter of brine will work beautifully to finish the cure. You can add fresh herbs to give your olives some additional flavor! You can eat your olives after a week, but they will store in the refrigerator for up to a year.
There are many other methods of preservation for olives, but olive oil is one of the most popular. To make this, wash and dry your fruit, then grind it – pits and all – into a paste. You will want it to be as fine of a paste as possible, and a food processor or blender can help with this once you’ve initially crushed the fruit. When you see oils start to form, it’s time to press your paste very well to extract all the liquids from it. When the liquids are extracted, let them sit for a few hours, then skim your oil off the top. It will last for a year or two.
Troubleshooting
Let’s discuss some of the most common problems you’re likely to encounter when growing olives. There aren’t lots, but those that exist are troublesome!
Growing Problems
Frost damage is a real concern for your olive trees. As stated earlier, there are temperatures that will damage or even kill trees. This is riskier for younger trees than older ones, as the older the tree is, the more it’s become adapted to your exact climate. Be careful to select trees that will work in your growing zone.
Pests
Scale insects (particularly olive scale, California red scale, black scale or parlatoria scale) can cause problems from die-back of foliage to a lack of fruit. They also produce honeydew, which can lead to the formation of sooty mold on branches or trunks. Applying a dormant oil around Thanksgiving, Christmas, and Valentine’s Day should prevent most scale insects from forming. For spot treatments, use dormant oil or neem oil.
Two forms of weevil, the apple weevil and garden weevil, can attack olives. They look like a very small beetle, and may travel from weeds or mulch at the soil level up into the tree where they feed on the foliage. Using a band of sticky paint such as tanglefoot trap around the trunk will reduce their numbers drastically.
Common in southern California, the olive psyllid is a sucking pest that will cause yellowing and curling of leaves. It also can reduce the eventual harvest by as much as 30%, making it a major problem for regions in San Diego, Orange, or Riverside counties. Treatment of these “jumping plant lice” is achieved by spraying them with insecticidal soap. Neem oil is also effective.
Another common pest in the warm southwestern US growing climate is the olive fruit fly. These irritating little fruit flies directly attack the fruit. If not controlled, they can reduce usable fruit yield drastically, even down to almost nothing. Yellow sticky traps work to identify the presence of the fruit fly. Apply a kaolin clay spray to coat fruit as it’s developing to prevent fly infestation of the fruit. Spinosad can be used to poison adult flies. Some forms of fruit fly bait are also effective at trapping them.
Diseases
Phytophthora root and crown rot can impact many types of fruit trees. Olives are particularly susceptible to this type of fungal rot. As it develops in overly-wet soils, the best way to prevent it from causing damage is to plant in well-draining soil. Avoid clay soils or other moisture-retentive growing media when planting an olive tree.
Anthracnose is a common fungal leaf spot that is easily treated with copper fungicides. Prevention is as easy as applying your dormant oil sprays at the appropriate times of year.
Olive knot is a bacterial disease spread easily into plant tissues during periods of excessively wet weather. It causes galls to develop on branches or even young olive tree trunks. The galls can cause girdling, preventing moisture from flowing through the wood and causing dieback. It is difficult to control, and may require a trained arborist’s assistance to treat with appropriate bactericides. Reduce the chances of olive knot on your olive tree by sterilizing between pruning cuts, avoiding freeze cracking of branches, or other open wounds to your tree.
Frequently Asked Questions
Q: How long does it take to grow an olive tree?
A: It depends on how old the tree is when you purchase it, but generally speaking you won’t start to see harvests for 3-4 years. There have been olive trees that have lived for hundreds of years when well-maintained, but expect a delay before you start reaping the benefits!
Q: Can you eat an olive off the tree?
A: Technically you can, as it won’t poison you. But olives on a tree are very bitter and should be cured properly after harvest to reduce the bitterness.
Q: Do olive trees produce olives every year?
A: Yes, on the prior year’s new growth. If you over-prune the prior year’s growth in late winter or early spring, you may not see heavy production in the next year.
