Olive Tree (Olea europaea)

Common olive, European Olive, Lady's Oil, Sweet Oil Plant, Olive Tree

Olive (Olea europaea) is an evergreen tree or shrub with great agricultural importance, especially in the Mediterranean. Its fruits are edible and widely used for making oil. Olive has acquired quite a few symbolic meanings during its long history of cultivation. The most popular symbol would probably be the olive branch, which represents peace and glory.

I. Appearance and Characteristics 

The olive, botanical name Olea europaea, meaning ‘European olive’, is a species of small tree or shrub in the family Oleaceae, found traditionally in the Mediterranean Basin. When in shrub form, it is known as Olea europaea Montra, dwarf olive, or little olive. The species is cultivated in all the countries of the Mediterranean, as well as in Australia, New Zealand, North and South America and South Africa. It is the type species for its genus, Olea. The tree and its fruit give their name to the Oleaceae plant family, which also includes species such as lilac, jasmine, forsythia, and the true ash tree.

The olive tree, Olea europaea, is an evergreen tree or shrub native to Mediterranean Europe, Asia, and Africa. It is short and squat and rarely exceeds 8–15 m (25–50 ft) in height. ‘Pisciottana’, a unique variety comprising 40,000 trees found only in the area around Pisciotta in the Campania region of southern Italy, often exceeds this, with correspondingly large trunk diameters. The silvery green leaves are oblong, measuring 4–10 cm (1+1⁄2–4 in) long and 1–3 cm (3⁄8–1+3⁄16 in) wide. The trunk is typically gnarled and twisted.

The small, white, feathery flowers, with ten-cleft calyx and corolla, two stamens, and bifid stigma, are borne generally on the previous year’s wood, in racemes springing from the axils of the leaves.

The fruit is a small drupe 1–2.5 cm (3⁄8–1 in) long when ripe, thinner-fleshed and smaller in wild plants than in orchard cultivars. Olives are harvested in the green to purple stage. O. europaea contains a pyrena commonly referred to in American English as a “pit”, and in British English as a “stone”.

II. How to Grow and Care

Sunlight

Olive trees prefer full sun, so make sure to place your tree in a spot that gets at least six hours of direct sunlight per day. They will thrive the best indoors in an unobstructed South or West window, but smaller specimens can tolerate Eastern light. Avoid placing your Olive trees in North windows since it only provides a low to moderate indirect light for plants.

 

Not sure if your space will provide enough light? Consider measuring light to ensure your Peace Lily will receive enough. If you find your space doesn’t provide enough light then consider installing a grow light to keep over the plant for 10-12 hours a day.

Temperature and Humidity

In their native Mediterranean climate, summers are hot and dry with low humidity and winters are cool and moist. For an olive tree grown indoors, a room temperature between 65 and 80 degrees Fahrenheit is best. Because it can withstand dry air, keeping it in a heated room of up to 40% relative humidity is fine. However, the plant should be kept away from heat vents and radiators to prevent drying out.

Watering

Olive trees are drought-tolerant and can be sensitive to overwatering. Allow at least half the soil to dry out between waterings, and make sure to provide good drainage. You can utilize a moisture meter to help you properly gauge soil moisture and avoid overwatering.

Soil

Olive trees will do well in a well-draining potting mix , such as a mix of pine bark, perlite, and compost. Olive trees can also grow well in rocky or gravelly soil but regular fertilizing would be required to make up for the lack of organic material.

Fertilizing

Olive trees in the landscape don’t need much fertilizer. Potted olives have slightly higher needs as fertilizer gets washed out of the potting soil, but they are still light feeders. Starting in the early spring and throughout the summer, feed the tree once a month with a balanced slow-release houseplant fertilizer. As for the amount, follow the label instructions, as the nutrient content of fertilizers varies. Stop fertilizing the tree in the fall and don’t fertilize it during its dormancy period in the winter.

Planting Instructions

Olive is generally grown with saplings. Because of its slow growth with long life expectancy, you should consider the best place where to plant your olive. Pick the sunniest spot possible in your garden, such as in front of a sunny wall. It can be even better to grow the tree in a raised bed which encourages soil drainage.

If growing it in a container, use a pot slightly larger than the root ball and place your pot somewhere sunny and warm. To promote growth, repot the olive every two to three years at the start of spring.

Pruning

Olive is a slow-growing plant so it does not require heavy pruning, except pruning to encourage growth when young. Ideally between late spring to summer, you can lightly prune to remove any dead and damaged parts of the plant. Then in summer, carry out a heavier prune for the pot trees if you want your olive to bear fewer fruits this year but save nutrients for yield next year. This heavier prune is also to ensure that sunlight can reach all parts of the plant including the center, which will encourage further growth. Be sure to remove any suckers, but do not remove any flowering branches which may be displaying fresh buds or fruits.

Propagation

Olive can be grown from both cuttings and seeds to produce a transplantable tree within a year. While it is more challenging to develop a olive from a seed due to its naturally low viability, it is possible by first cracking the seed and then soaking it in room temperature water for 24 hours before sowing at the end of spring. Carefully keep the temperature for germination at about 15 ℃, water when the topsoil is dry to keep the soil moist, and wait for a month. Generally, your olive should germinate in the second month.

Comparing to seeds, it is recommended to propagate your olive through a cutting to increase the chance of successful establishment. To do this, first take a semi-hardwood cutting, roughly 15 to 30 cm long, with multiple leaves. This cutting must not have any active buds, so it is best to take this cutting in summer once the plant has stopped blossoming and before growing fruit. plant in light soil, keep it out of direct sunlight, ensure that the temperature is between 18 to 20 ℃ and water daily. Roots should begin to take hold after 2-3 months.

Potting and Repotting 

It’s time to repot your tree when the roots reach the sides of the container or grow out of the drainage holes. Olive trees grow slowly so your plant might not require repotting for two to three years.

The new container should be 25 percent larger than the root ball, or at least 2 inches larger than the root ball all around. Make sure that in the new container, the stem is above the soil level and not buried, as this could lead to root rot.

Overwintering

When nighttime temperatures drop below 40 degree Fahrenheit in the fall the tree should be brought indoors. Gradually acclimate it to the lower light conditions by placing it in a partially shaded location for about one week, then bring it back inside.

Olive trees attract ants, scale insects, and spittlebugs. To avoid bringing them inside, give the tree a thorough spray with a hose (cover the soil with a piece of plastic while hosing it off so you don’t drench the soil).

Moving Outdoors for the Summer

If you are able, you should move your tree outdoors during the warm months. Wait until nighttime temperatures are consistently above 40 degrees Fahrenheit, to avoid cold or frost damage. The tree should be adjusted gradually to outdoor conditions. Start by placing it in a spot where it is sheltered from wind and full sun for several days. After that, you can put it in its permanent summer location.

III. Uses and Benefits 

The olive tree, Olea europaea, has been cultivated for olive oil, fine wood, olive leaf, ornamental reasons, and the olive fruit. About 80% of all harvested olives are turned into oil, while about 20% are used as table olives. The olive is one of the “trinity” or “triad” of basic ingredients in Mediterranean cuisine, the other two being wheat for bread, pasta, and couscous; and the grape for wine.

  • Ornamental uses

In modern landscape design olive trees are frequently used as ornamental features for their distinctively gnarled trunks and “evergreen” silvery gray foliage.

  • Culinary uses

Table olives are classified by the International Olive Council (IOC) into three groups according to the degree of ripeness achieved before harvesting:

  • Green olives are picked when they have obtained full size, while unripe; they are usually shades of green to yellow and contain the bitter phytochemical oleuropein.
  • Semi-ripe or turning-color olives are picked at the beginning of the ripening cycle, when the color has begun to change from green to multicolour shades of red to brown. Only the skin is coloured, as the flesh of the fruit lacks pigmentation at this stage, unlike that of ripe olives.
  • Black olives or ripe olives are picked at full maturity when fully ripe, displaying colors of purple, brown or black. To leach the oleuropein from olives, commercial producers use lye, which neutralizes the bitterness of oleuropein, producing a mild flavor and soft texture characteristic of California black olives sold in cans. Such olives are typically preserved in brine and sterilized under high heat during the canning process.
  • Other uses

Olive wood

Olive wood is very hard and tough and is prized for its durability, colour, high combustion temperature, and interesting grain patterns. Because of the commercial importance of the fruit, slow growth, and relatively small size of the tree, olive wood and its products are relatively expensive. Common uses of olive wood include: kitchen utensils, carved wooden bowls, cutting boards, fine furniture, and decorative items. 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.

Olive oil

Olive oil is a liquid fat obtained from olives, produced by pressing whole olives and extracting the oil. It is commonly used in cooking, for frying foods or as a salad dressing. It is also used in cosmetics, pharmaceuticals, and soaps, and as a fuel for traditional oil lamps, and has additional uses in some religions. Spain accounts for almost half of global olive oil production; other major producers are Portugal, Italy, Tunisia, Greece and Turkey. Per capita consumption is highest in Greece, followed by Italy and Spain.

The composition of olive oil varies with the cultivar, elevation, time of harvest and extraction process. It consists mainly of oleic acid (up to 83%), with smaller amounts of other fatty acids including linoleic acid (up to 21%) and palmitic acid (up to 20%). Extra virgin olive oil is required to have no more than 0.8% free acidity and fruity flavor characteristics.

IV. Harvesting and Storage

In general, it takes 2-5 years before olive will begin to bear fruit, for young trees this duration should be at least four years. It prefers a warm climate with a cooler winter (below 10 ℃) to produce fruit. Because of this, the fruit is rarely produced in colder climates, such as Britain, unless kept in a greenhouse with special care.

Olive is mostly grown for its useful properties, especially its fruit. In summer, it will bloom tiny white flowers before producing edible green fruits that ripen to darker color according to cultivars. Known as olives, this fruit is harvested in late fall by picking with hands. While some olives are edible rawly, some others require curing first before they are palatable. There are various curing ways, such as soaking them in saltwater for weeks at a time.

Olive Tree (Olea europaea) Details

Common name Common olive, European Olive, Lady's Oil, Sweet Oil Plant, Olive Tree
Botanical name Olea europaea
Plant type Tree
Hardiness zone 8a, 8b, 9a, 9b, 10a, 10b
Growth rate Slow
Harvest time Fall
Height 20 ft. 0 in. - 30 ft. 0 in.
Width 20 ft. 0 in. - 30 ft. 0 in.
Sunlight Full sun (6 or more hours of direct sunlight a day)
Soil condition Clay
Flower color White
Leaf color Gray/Silver