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Crop Guide: Olives

General information
Growing olives
The mineral nutrition of olive trees
Fertilization practices
Haifa's recommendations
Appendix I & II
Index:
  1. Origin and history
  2. Plant description and physiology
  3. Worldwide cultivation of olives
  4. Olive cultivars
  5. Yields
 
 
Scientific name: Olea europaea L.
Family: Oleaceae
Related species: Wild Olive (Olea africana), Oleaster (O. europaea var. oleaster).
Distant affinity: American Olive (Osmanthus americana), Fragrant Olive (O. fragrans).
Common names: English: Olive. French: Olivier; Spanish: Olivo; Italian: Olivo; German: Olive; Arabic: Zeitoun
 
1.1 Origin and history
Olive cultivation dates back more than 6,000 years and it is still flourishing today, not only in its countries of origin, but now in most areas of the world.
 
The olive is native to the Mediterranean region, tropical and central Asia and various parts of Africa. The olive has a history almost as long as that of Western civilization, its development being one of civilized man's first accomplishments. At a site in Spain, carbon-dating has shown olive seed found there to be 8,000 years old. The cultivation of O. europaea may have been initiated independently in both Crete and Syria. Archeological evidence suggests that olives were grown in Crete as long ago as 2,500 B.C. From Crete and Syria olives spread to Greece, Italy and other parts of the Mediterranean area.
 
The leafy branches of the olive tree have been used for thousands of years as a symbol of abundance, glory and peace, such as to crown the victors of friendly games and bloody wars. As emblems of benediction and purification, they were also ritually offered to deities and powerful figures; some were even found in Tutankhamen's tomb.
 
Over the years, the olive has been the symbol of peace, wisdom, glory, fertility, power and pureness. The olive tree and olives are mentioned over 30 times in both the New and Old Testaments of the Bible. It is one of the first plants mentioned in the Bible, and one of the most significant. For example, it was an olive leaf that the dove brought back to Noah to demonstrate that the flood was over.
 
An olive tree in Algarve, Portugal, is 2,000 years old, according to radiocarbon dating. The age of an olive tree in Crete, claimed to be over 2,000 years old, has been confirmed on the basis of tree ring analysis. According to a recent scientific survey, there are dozens of ancient olive trees throughout Israel and Biblical Palestine, 1,600-2,000 years old. Ancient trees include two giant olive trees in Arraba and five trees in Deir Hanna (both in the Galilee region), which have been determined to be over 3,000 years old, although the credibility of the study that produced these dates has been questioned. All seven trees still bear olives.
1.2 Nutritional and health values of the olive fruit
The nutritional value of the olive stems from the fact that it has very little carbohydrate and is a great source of monounsaturates. This makes it a good element in a low-carbohydrate diet. There are many different types of olives and the broad categories are the green olives and the ripe black olives. Olives
are a rich source of polyphenols, which are critical as our body’s defense against cancer. Polyphenols have many good properties, and these elements, which are the reason for the taste and the smell of the olive, can also help as an anti-inflammatory.
 
Olive oil
Olive oil, which is extracted by pressing olives, is also a good source of many beneficial nutrients and minerals. The oil is a good source of antioxidants and, as a special bonus, it greatly adds to the flavor of dishes. As it contains monounsaturated fat, it does not elevate the level of cholesterol in the body. It is said that olive oil prevents the adherence of cholesterol to the walls of the artery. Additionally, monounsaturated fats also help in controlling blood sugar. This affects the insulin regulation in the body in a positive way.
 
In terms of their phytonutrient content, olives are nothing short of astounding. Few high-fat foods offer such a diverse range of antioxidant and anti-inflammatory nutrients, some of which are unique to olives. The following list specifies only the most important phytonutrient categories: Simple Phenols; Terpenes; Flavones; Hydroxycinnamic acids; Anthocyanidins; Flavonols; Hydroxybenzoic acids and Hydroxyphenylacetic acids.
 
According to the USDA, a single serving of 10 medium-sized green olives contains the following:
 
 
Table 1.1: The nutritive value of 10 medium-sized green olives
Energy
49 kcal
Vitamin A
7 mcg
Protein
0.35 g
Vitamin B1
0.007 mg
Fat, total
5.21 g
Vitamin B6
0.01 g
Carbohydrates
1.31 g
Niacin (Vitamin B3)
0.08 mg
Dietary fiber
1.1 g
Vitamin E
1.3 mg
Saturated fatty acids, total
0.69 g
Lutein + zeaxanthin
173 mcg
Monounsaturated fatty acids, total
3.85 g
Choline, total
4.8 mg
Polyunsaturated fatty acids, total
0.44 g
Folate
1 mcg
Calcium
18 mg
Beta-carotene
79 mcg
Magnesium
4 mg
Iron
0.17 mg
Potassium
14 mg
Sodium
529 mg
Phosphorous
1 mg
Zinc
0.01 mg
Copper
0.04 mg
Selenium
0.3 mcg
 
 
1.3 Plant description and physiology
The olive tree is an evergreen tree or shrub, short and thick, and rarely exceeds 8 – 15 meters in height. Olives are long-lived with a life expectancy of 500 years. The trees are also persistent, easily sprouting back even when chopped to the ground.
 
The trunk is typically crooked and twisted. The bark of the tree is pale gray. It has many thin branches with opposite branchlets. The leaves are opposite each other and are feather-shaped or elliptic, measuring 4 – 10 cm long and 1 – 3 cm wide. They are smooth and pale green on top and silvery on the bottom and their skin is rich in tannin, which gives the mature leaf a grayish-green hue. The leaves are replaced every two to three years, leaf-fall usually occurring at the same time that new growth appears in the spring.
 
Flowers
Olive trees produce two different types of creamy white flowers, a perfect flower, which contains both male and female parts, and a staminate flower with stamens only. The small white, feathery flowers, with ten-cleft calyx and corolla, two stamens and bifid stigma, are borne generally on the last year's branches, in racemes springing from the leave's axils. The flowers are largely wind pollinated with most olive varieties being self-pollinating, although fruit-set is usually improved by cross pollination with other varieties. There are self-incompatible varieties that do not set fruit without other varieties nearby, and there are varieties that are incompatible with certain others. Incompatibility can also occur for environmental reasons such as high temperatures.
 
 
Flower induction and fruit-set
The tree is mature enough to produce flowers and fruits at the age of about four years. Changes affecting fruit-set start in the preceding summer.
  • Absence of water stresses during preceding summer assists the change from vegetative buds into flower buds.
  • Other stresses, like pests, diseases and nutrient deficiency, can severely affect fruit development and yield.
  • Optimal status during July and August is critical for ensuring a tree is in peak condition to produce maximum flowers.
  • Dry-land trees can have as many as 52% sterile (staminate) flowers, compared to suitably irrigated trees with only 7% – 8% of sterile flowers.
  • Trees must be exposed to winter chill to bear fruit. Average temperature for winter should be 120 Celsius or somewhat less for adequate chilling.
  • Hot, dry winds during flowering will tend to increase flower drop and reduce fruit-set.
  • Flowering in the northern hemisphere usually occurs in September – October, depending on variety and conditions.
  • Olive trees in suitable environments produce abundant pollen.
  • Correct irrigation and windbreaks reduce the detrimental effects of heat and wind on fruit-set.
 
The fruits are a green drupe 1 – 2.5 cm long, becoming generally blackish-purple when fully ripe. A few varieties are green when ripe and some turn a shade of copper brown. The cultivars vary considerably in size, shape, oil-content and flavor. The shapes range from almost round to oval or
elongated with pointed ends. Raw olives contain a bitter alkaloid (oleuropein) that makes them bitter and unpleasant, but not harmful to health. This means that the fruit cannot be consumed directly from the tree and has to undergo curing processes. Some olives are, however, an exception to this rule because as they ripen they sweeten right on the tree; in most cases this is due to fermentation. One case in point is the Thrubolea variety in Greece. A few varieties are sweet enough to be eaten after sun drying.
 
Thinning the crop will give a larger fruit size. Wild varieties are thinner-fleshed and smaller than in orchard cultivars. They can be either almost round to oval, and the fleshy part is filled with oil. It contains a single seed, commonly referred to as a pit or a rock. When fully mature, the fruit becomes very dark purple. Olives are harvested at the green to purple stage. Canned black olives may contain chemicals (usually ferrous sulfate) that turn them black artificially.
 
Figure 1.1: A 19th century illustration of the different parts of an olive tree.
 
1.4 Worldwide cultivation of olives
Spain, Italy, Greece, Turkey, Syria and Morocco are the world's major olive oil producing countries, accounting for some 83% of world olive oil output, and a similar percentage of consumption. A large olive production industry is also found in California, Australia and South Africa.
 
 
Table 1.2: Main olive-producing countries in 2009 (Source: FAOSTAT)
 
Production
(Tons)
Cultivated area
(ha)
Yield
(Ton/ha)*
World
18,241,809
9,922,836
1.83
Spain
6,204,700
2,500,000
2.48
Italy
3,600,500
1,159,000
3.11
Greece
2,444,230
765,000
3.14
Turkey
1,290,654
727,513
1.77
Syria
885,942
635,691
1.39
Morocco
770,000
550,000
1.4
Tunisia
750,000
2,300,000
0.33
Egypt
500,000
110,000
4.55
Algeria
475,182
288,442
1.65
Portugal
362,600
380,700
0.95
Lebanon
76,200
250,000
0.65
Jordan
189,000
126,000
1.5
Libya
180,000
 
 
Argentina
160,000
52,000
3.08
 
*All ton terms in this publication are metric, unless otherwise indicated.
(Source: OLIVÆ, Official magazine of the International Olive Council)
 
 
 
1.4.1 Dynamics of production and consumption of table olives
Figure 1.2: World production and consumption of table olives (1990/91–2010/11)
(Source: OLIVÆ, Official magazine of the International Olive Council)
 
1.4.2 Olive oil
World olive oil consumption rose by 1 million tons during 1996-2009, while olive oil production for 2009 is estimated at close to 2.9 million tons (Figure 1.3). As the oil production coefficient from the fruit is around 0.153, the said oil production figure represents some 19 million tons of olive fruit that were produced for oil extraction.
 
The perceived health benefits, a continuing interest in Mediterranean cuisine and promotion by the controlling body of the industry, the International Olive Oil Council, are all stimulating market demand for olive oil, particularly in countries not traditionally associated with olive oil, such as the United States and Japan.
 
 
There are a number of classifications of the different grades of olive oil, with the top one being Extra Virgin Olive Oil.
 
Extra Virgin & Virgin Olive Oil (EVOO & VOO) are the healthiest grades of olive oil; they have the most flavor and aroma. EVOO & VOO are extracted using only mechanical means, without the use of chemicals or excessive heat. EVOO must be free of defects and have an acidity of 0.8% or less; VOO should have an acidity of 2% or less.
Pure Olive Oil is a middle of the line olive oil. It is usually a mixture of refined and virgin olive oil and can be used for cooking or frying, etc.
Extra Light is a lower grade of olive oil and is usually refined olive oil. The term "light" usually refers to it being lighter in color, flavor and aroma. Being refined oil, it has also had some of the health benefits removed from its makeup.
 
Figure 1.3: World olive oil production, 1990–2009 (million tons)
(Source: OLIVÆ, Official magazine of the International Olive Council)
 
1.5 Olive cultivars
There are two basic products: olive oil and table olives. Olive oil products dominate the marketplace and 80% to 90% of olives produced are devoted to olive oil production. Most interest is in producing high quality extra virgin (EV) olive oil, for which there is good demand.
 
 
Over the centuries mankind has produced and propagated a myriad of olive varieties. Most were selected for one use only, generally oil production. In recent decades, however, some new varieties were bred for a dual purpose, oil production and as table olives. One of these is Barnea, which was developed in Israel and is very popular in new, modern plantations, e.g., Australia. Today several dozen varieties are grown commercially around the world. DNA typing shows that some varieties with different names are actually the same. All have their own particular characteristics, such as: oil yield, organoleptic (taste and smell) characteristics, resistance to stress, productivity, tree vigor, time of ripening and ease of harvest.
 
There are many aspects to be considered simultaneously when deciding on the variety mix of an olive grove. Local conditions, productivity and oil or fruit quality are some of the important factors that should be evaluated. Tolerance or sensitivity to different pests, diseases or climatological conditions, together with pollination and ripening periods, are important points to evaluate in the final layout of the grove.
 
Varieties such as Leccino, Picual, Pendolino, Arbequina, Picholine orHojiblanca have proven in the Mediterranean area to be more tolerant to cold temperatures than other varieties. Varieties such as Frantoio, Manzanillo or Barnea are considered to be moderately to highly sensitive to frost damage.
Since many cultivars are self-sterile or nearly so, they are generally planted in pairs with a single primary cultivar, and a secondary cultivar for cross-pollination, to optimize yield. In general, it is best to have at least three to four different varieties to optimize cross-pollination.
 
In recent times, efforts have been directed at producing hybrid cultivars with qualities such as resistance to disease, quick growth and larger or more consistent crops.
Following is a list of some particularly important olive cultivars arranged in alphabetical order:
 
  • Amfissa is an excellent quality Greek table olive grown in Amfissa, Central Greece. Amfissa olives enjoy protected designation of origin (PDO) status, and are equally good for olive oil extraction.
  • Arbequina is a small, brown olive grown in Aragon and Catalunia, Spain, good for eating and for oil.
  • Ascolano, Very large, ellipsoidal fruit. Skin color very light even when ripe, pit very small. Fruit is tender and must be handled carefully. Contains very little bitterness and requires only moderate lye treatment. Excellent for pickles, but needs proper aeration during pickling to develop "ripe" color. Tree is a heavy bearer, widely adapted.
  • Barouni, Large fruit, almost as large as Sevillano. Trees spreading and easy to harvest. Withstands extremely high temperatures. This variety is usually used for making home-cured olives. Originally from Tunisia.
  • Barnea is a modern dual-purpose cultivar bred in Israel to be disease-resistant and to produce a generous crop. The oil has a strong flavor with a hint of green leaf. Barnea is widely grown in Israel and in the southern hemisphere, particularly in Australia and New Zealand.
  • Bosana is the most common olive grown on Sardinia. It is used mostly for oils.
  • Chemléli Sfax,a Tunisian vigorous tree, which is productive and resistant to the arid conditions, has fruity oil mainly at the start of the harvest period with pleasant flavors of green almond and high health values due to its high sterol content.
  • Chetoui, the second principal variety of olive tree in Tunisia gives a fruity oil with green almond flavors and contains very high (> 300 ppm) phenolic compound which guarantees to this variety a stability against oxidation.
  • Cornicabra, originating in Toledo, Spain, comprises about 12% of Spain's production. It is mainly used for oil.
  • Empeltre, from Pedrola, Aragon, is a medium-sized black olive grown in Spain. Especially in Aragon and the Balearic Islands, it is dual purpose.
  • Frantoio and Leccino cultivars are the principal raw material for Italian olive oils from Tuscany. Leccino has a mild, sweet flavor, while Frantoio is fruity with a strongeraftertaste. Due to their highly valued flavor, these cultivars are now grown in other countries.
  • Gemlik is a variety from the Gemlik area of northern Turkey. It is a small to medium sized black olive with high oil content. This type of olive is very common in Turkey and is sold as a breakfast olive in cured formats. The sign of a traditionally cured Gemlik olive is that the flesh comes away from the pit easily.
  • Gordal is a medium to large, plump fruit, ripening early. It resembles Sevillano. A popular pickling olive and principal cultivar in Spain.
  • Hojiblanca originated in the province of Córdoba, Spain; its oil is widely appreciated for its slightly bitter flavor.
  • Kalamata, a large, black olive with a smooth and meat-like taste, is named after the city of Kalamata, Greece, and is used as a table olive. These olives are usually preserved in wine, vinegar or olive oil. Kalamata olives enjoy PDO status.
  • Koroneiki originated from the southern Peloponese, around Kalamata and Mani in Greece. This small olive, though difficult to cultivate, has a high yield of olive oil of exceptional quality.
  • Manzanillo or Manzanilla, "Manzanillas" means "little apples" in Spanish. A large, rounded-oval fruit, it originated in Dos Hermanas, Seville, in southern Spain. Known for its rich taste and thick pulp, it is a prolific bearer, grown around the world. Its skin is a brilliant purple, changing to deep blue-black when mature. It resists bruising and ripens early, several weeks earlier than Mission. The pulp parts readily with its bitterness and is exceedingly rich when pickled. Excellent for oil and pickles. Tree spreading and vigorous.
  • Lucques is found in the south of France (Aude département). It is a green, large and elongated fruit. The stone has an arcuated (bow) shape. Its flavor is mild and nutty.
  • Maalot (Hebrew for merits) is a disease-resistant, eastern Mediterranean cultivar derived from the North African Chemlali cultivar. The olive is medium sized, round, has a fruity flavor and is used almost exclusively for oil production.
  • Mission originated on the California Missions and is now grown throughout the state. It is more cold resistant than other cultivars. It is a black, medium sized, oval fruit and is generally used for table consumption. Skin deep purple changing to jet-black when ripe. Flesh very bitter but firm, freestone. Ripens rather late. Good for pickling and oil, specially ripe pickles. Most widely used for cold-pressed olive oil in California. Tree vigorous, heavy-bearing.
  • Nabali, a Palestinian cultivar, also known locally as Baladi, which, along with Souri and Malissi, is considered to produce among the highest quality olive oil in the world.
  • Picholine, is grown in the south of France. It is green, medium sized, and elongated. The flavor is mild and nutty. Small, elongated fruit. Its skin is light green, changing to wine red, then red-black when ripe. The pulp is fleshy and firm-textured. The tree is vigorous and medium-sized and bears heavy crops regularly. Cured olives have a delicate, subtle, lightly salty, nut-like flavor. Usually salt-brine cured. Popular in gourmet and specialty markets.
  • Picual, from the province of Jaén, southern Spain, is the most widely cultivated olive in Spain, comprising about 50% of Spain's olive production and around 20% of world olive production. It has a strong but sweet flavor, and is widely used in Spain as a table olive. Moreover, its oil has some of the best chemical properties found in olive oil, being the richest in oleic acid and vitamin E.
  • Rubra is a medium-small, ovate fruit. Its skin is jet-black when ripe. It ripens 3 to 4 weeks earlier than Mission. It is best suited for oil, but is also used for pickling. The tree is large and precocious, often producing fruit the second year. An exceptionally prolific bearer. Very hardy and reliable, even in dry situations. Originated in France.
  • Sevillano is a very large fruit, bluish-black when ripe. The stone is large and clinging. The fruit ripens early and has a low oil content; it is only useful for pickling. It is used for making Sicilian style salt brine cured olives and is also the leading canning cultivar. The tree is a strong grower and a regular bearer. It requires a deep, rich, well-drained soil and will not stand much cold.
  • Souri, grown in Lebanon near the town of Sur (Tyre) and widespread in the Levant, has a high oil yield and exceptionally aromatic flavor.
Some other varieties are very important in their original countries, as follows:
GREECE:
 
  • Gaidoroelia, which means donkey-olive, owes its name to its large size. Usage: Table olive. Characteristics: Large. Found mainly in northern Greece, especially in Chalkidiki.
  • Conservolea. Usage: Table olive. Characteristics: 80% of Greek table olives belong to this variety and carry several local names. It is oval or round, 5-8 grams and it is served with salty food.
  • Koroneiki. The name derives from the Greek word "korona" which means crown. Usage: Mainly for oil production. Characteristics: The produced oil has a very light and harmonious aroma, often with a light lemon fragrance.
  • Kothreiki. Usage: Table olive and oil production. Characteristics: Similar to Conservolea in size and color.
  • Megara. Usage: Table olive and oil production. Characteristics: Small, green in tin and black in salty curing.
  • Stafidoelia, which means raisin olive. Usage: Table olive. Characteristics: It doesn’t need to be processed. It gets black on the tree from maturity until it shrinks. Can be placed in a tin with some salt or oil.
  • Throuba. Usage: Table olive. Characteristics: Small to medium fruit. It loses its acidity by maturing on the tree. Its bitter ingredients are lost due to a microorganism.
ITALY: Cipresino; Coratina; Grappoio; Intrana; Moraiolo; Pendolino;  Santa Caterina; Taggiasca.
 
1.6 Yields
Traditional, extensive, rain-fed olive plantations yield ranges between 7 and 14 ton / ha, which transforms to 1,700 – 2,400 liters of oil, according to a coefficient of ~170 liters of oil per ton of fruit.
Intensively cultivated, super-high density olive plantations, 5 years old or more, yield an average of 24 ton / ha, which transforms to 4,560 liters of oil, according to a coefficient of ~190 liters of oil per ton of fruit.
Expected yield of table olives range: 14 – 32 tons/ha and the harvest removal rate range is 60% – 80%.
The following figures can be used as a guide to expected yields for a mature, fully irrigated olive grove (Table 1.3). The expected yield for non-irrigated crops is substantially lower.
 
 
Table 1.3: Expected yield of mature and fully irrigated olive trees
Annual yield of fresh olives per tree
50 kg
% oil in oil varieties
20%
Mass of olive oil per tree
10 kg
Specific mass of olive oil
0.9 kg/liter
Oil production per tree
11.1 liters
Tree planting spacing
8m x 5m
Tree density
250 per hectare
Yield of fresh olives per hectare
12.5 ton
Liters of olive oil per hectare
2,778 liters
 
 
Need more information about growing olives? You can always return to the olive tree fertilizer & olive crop guide table of contents