Olive

Plant Characteristics

Cultivation

Scientific Names

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Read about Olive in the Standard Cyclopedia of Horticulture

Olive. A small evergreen tree grown for its drupes which yield oil and are also prepared as a food and condiment. The cultivated olive (Olea europaea) is the typical species of the genus Olea (Fig. 2570). It is found growing wild in various countries from the Punjab to Morocco and the Canary Islands and on both sides of the Mediterranean from the slopes of the Atlas to southern France and Macedonia where moisture and temperature conditions are favorable. It is particularly abundant in Syria and Algeria. The wild form has small rigid leaves and a fruit with 'little flesh and is sometimes considered as a distinct botanical variety under the name of oleaster or Oka sylvestris (see Olea). It is used as a stock on which to graft the cultivated forms and in Algeria the government encourages the utilization of wild trees by grafting in place (Fig. 2571). The cultivated olive is grown throughout the same region and, with the aid of irrigation, m localities too dry for its naturalization. It has been grown from prehistoric times in Asia Minor where it seems to have originated. Its culture was introduced into all Mediterranean countries by the Phoenicians, Greeks, and Romans. In modern times it has been widely dispersed by colonists in America, Australia, and South Africa. In the United States the olive succeeds only in California and in parts of Florida, Arizona, and New Mexico. It was planted at the missions by the Franciscan padres and from the trees grown there came the variety now known as the Mission, which is still preferred to all other varieties by most growers. The original trees were grown at the San Diego Mission from seeds brought from Mexico. Like the Mission grape, the Mission olive has not been identified with any Old World variety and is probably a seedling. Some growers distinguish several forms or variations of the Mission, differing in size and form of leaf, fruit, and tree. The correctness of this view seems probable from the mode of its origin, but others consider these differences to be due simply to variations of soil and climate. The olive thrives in all soils providing they are deep and well drained, but the crops are in proportion to the fertility of the soil. The olive will often make a handsome vigorous tree in dry situations unsuited to most fruits, provided the subsoil will allow of deep penetration of the roots. Paying crops are obtained, however, only on fairly fertile soil and with intelligent and thorough cultivation. It requires a slightly greater annual sum of heat than the vine and is more sensitive to winter cold, which should never fall below 14° F., nor frequently below 19° F. A clear dry atmosphere is favorable. Summer rains or fogs render the tree subject to the attack of the black scale, which is very harmful and difficult to control on the olive. Suitable situations and paying orchards are found in California from the upper end of the Sacramento Valley to the borders of Mexico in Imperial County. Most of the paying orchards are on the slopes of the Sierras at moderate elevations, in southern California, and widely scattered through both the Sacramento and the San Joaquin valleys. There are a few good orchards in favored locations in the inner coast valleys from Sonoma southward. Olive-growing promises to be very successful in the Imperial Valley. The suitability of California for olive-growing began to be generally recognized between 1880 and 1890 and many orchards were planted during this period. The expectations of large profits were not as a rule realized when the trees came into bearing. Several causes contributed to this. The oil could not compete with the cheap cottonseed oil which was often sold as "pure olive oil;" the ripe pickled olives were a novelty and their merits not understood in the East and the first attempts to manufacture green pickled olives were unsuccessful. Many orchards were accordingly uprooted and few trees were planted during the next fifteen years. Recently effective pure-food laws have removed much of the competition of imported and domestic cottonseed oil, the taste for ripe pickled olives has been acquired by a large body of consumers and the methods of producing green pickles have been perfected. Few of the last, however, are made, as the demand for good ripe pickles exceeds the supply. Olive- growing has therefore been on a profitable basis for some years and large new plantations have been made during the last five years. No reliable statistics of the olive industry are available but the statistician of the California State Board of Agriculture places the number of trees in California at 1,530,000, which corresponds to something under 30,000 acres. The same authority credits Florida with 8,000 trees, Arizona with 1,600 and all other states with 200. The State Board of Equalization, however, placed the number of trees in California in 1912 at only 700,000, or about 14,000 acres. It is estimated that California produced in 1910 about 800,000 gallons of olive oil and 1,000,000 of pickled olives. For 1911, the oil output is placed at 920,000 gallons and the pickles at 1,150,000 gallons. If one ton of olives is reckoned to yield thirty-five gallons of oil and that it requires six pounds of olives to make one gallon of pickles, the crop of 1911 represents about 31,000 tons of fruit, of which 85 per cent were used for oil and only 15 per cent for pickles. If the average of the estimates of total acreage given above is taken, the crop is equivalent to 1.4 tons to the acre. When it is considered that many orchards are planted with poor bearing varieties and hi unfavorable situations, this average is satisfactory. According to the state statistician, six counties of the San Joaquin and Sacramento valleys produced in 1900 nearly 75 per cent of the crop of the whole state, though having but 25 per cent of the trees. This indicates a variation of crop of less than half a ton to over four tons to the acre, according to locality. In the south of France 2.7 tons to the acre is considered a maximum yield and good well-cultivated orchards are not expected to average more than 1.3 tons. Using the estimates given above, it will be seen that pickles were made from only about 15 per cent of the crop, the remainder being used for oil. The reason for this is that while pickled olives of suitable quality arc more profitable than oil, only the large olives are acceptable to the market. During the first period of heavy planting, a large number of the trees used were of varieties suitable for oil, which are all of small or medium size. Even when large-fruited varieties are planted, there will always be a large proportion of the fruit undersized, especially in poor soil and hi unfavorable localities. At present the tendency is to plant only those varieties which are capable of producing large fruit but which at the same time are rich in oil of good quality. The pickled olive is thus considered the main crop and the oil a kind of supplementary or byproduct. From this point of view, the Mission olive, when propagated from selected trees in favorable localities, is perhaps the best variety. Pickling and oil- making tend to concentrate in large central establishments in each olive-growing center. This makes it possible to employ the best methods and machinery in the hands of trained men. The results are great improvement in quality of the product and economy of operation. The price paid for olives fell at one tune to $15 a ton which, with the average crop, represents gross returns of $25 or $30 an acre, which in most cases would not pay the cost of cultivation and harvesting. It has risen gradually until during the last few years $100 a ton has been paid for olives suitable for pickling and even $150 to $200 a ton for very large fruit. This represents average gross returns of about $150 or more to the acre and is very profitable, as the large olives are gathered much more cheaply than the small. When turned into pickles, a ton of olives represents $250 at the low retail price of 75 cents a gallon, but a ton of olives will yield oil of a value of only about $87.50 at the ordinary price of $2.50 a gallon. As olives are usually bought ungraded, the buyer of pickling olives at present prices incurs a loss on all the small olives he uses for oil. The price paid for oil olives too small for pickling is less than half that paid for the large fruit. Propagation. Olives in California are usually grown from cuttings taken from the tree when it is most dormant, that is, in January and February. These cuttings may be of any size and taken from any part of the tree. Most nurserymen prefer to use "tips. These are the mature ends of shoots 4 to 5 inches long. Two or three of the upper leaves are left or trimmed back a little and the remainder removed entirely. They are then planted in boxes of sand under glass with artificial heat and, after rooting, transplanted to the nursery where they remain for one, two or three years before being planted in place. When a greenhouse is not available, larger cuttings of older wood are preferable. These cuttings are usually made about 14 inches long and may be from ¾ to 1½ inches in diameter. Their rooting may be facilitated by splitting or scratching the bottom 2 or 3 inches with a knife. In Spain, large branches of old trees are used to produce young plants. These branches (truncheons) are cut into convenient lengths and incisions reaching half way to the center made every 3 or 4 inches. The sections are then placed horizontally in trenches about 10 inches deep, where they are covered with soil, and watered. Shoots arise near the saw-cuts and when sufficiently developed they are removed with the roots which have formed, and planted in the nursery. This method, formerly employed in California, is now little used there. Suckers taken from the base of the trunk with a plate of the old wood attached to the base are sometimes used and root more easily than ordinary cuttings. Olives may also be propagated by seeds, which are supposed to give a stronger root-system and more fruitful trees. The seedlings, however, must be grafted and it takes a little longer to obtain a tree by this means. The Mission and many other cultivated varieties have large seeds which are hard to germinate. Small- fruited varieties, such as the Redding and Chemlali, which resemble the wild olive, are the best. The completely ripe olives are placed in a heap until the pulp becomes soft enough to be removed easily. Usually the stones are then treated for twelve to twenty-four hours in a 10 per cent solution of caustic soda. The process must be carefully watched by breaking a stone occasionally and the lye removed before it penetrates to the kernel. The treated pits are kept in moist sand until March or April, when they are planted rows. Many will not germinate the first, year and many not at all. Much time may be saved by clipping off the apex of the olive pit. Seeds treated in this way will germinate readily in a few weeks. By means of a simple device originated by the California Experiment Station, this clipping can be done very rapidly (Fig. 2572). The second or third year, the young seedlings are transplanted to nursery rows in good rich soil, where they are budded or grafted the following spring. One or two years later, they are ready to be planted in the orchard. The planting distances vary with the nature of the soil and of the variety. The trees in some orchards are planted as near as 20 feet, but more at 24 to 30. The olive is very long in reaching its full size, and some growers plant at 20 or 24 feet with the intention of taking out three-quarters of the trees when they begin to crowd, leaving them 40 to 48 feet apart. It is not, however, until the trees are twenty-five or thirty years old that they reach full size, and most growers prefer to plant at intermediate distances of about 30 to 36 feet. In France, the distances adopted vary from 15 feet in the most northerly districts to 24 feet in the more southerly. In Algeria, from 30 to 36 feet are the usual distances, while in Tunisia 45 feet and even 60 to 72 feet are adopted, usually with intercalary annual crops. Most of the olives in California are planted in solid orchards, but many are used as avenue and border trees. Seedling olives arc grafted in the nursery. This may be done when the seedlings are one year old, by means of a side- or whip-graft in early spring, or of a twig-bud after the sap is flowing freely. The graft is made at or near the surface of the ground. Older seedlings may be crown-grafted or twig-budded higher up in late spring. Old trees may be grafted to change to a more desirable variety. Much grafting of this kind has been done in California, the large pickling varieties being grafted on small oil olives or on the strong-growing Redding, which bears a worthless fruit and was at one time planted largely in the mistaken belief that it was the large-fruited Picholine. The trees may be cut back to the main branches and crown-grafted immediately or allowed to form a growth of new shoots, which are budded the following year. Much care and work are necessary for several years to prevent the growth of suckers from the old stocks. Cultivation and pruning. The planting and cultivation of the olive require the same care as in the case of other fruits. Where the rainfall is ample, thorough cultivation may insure sufficient soil-moisture, but in most cases irrigation is necessary. Cutting back and the removal of ill-placed branches is advisable during the first and second years, and the tree should be allowed to make only one trunk. After the second year, the lower branches should be gradually removed until a clean trunk of 2 or 3 feet is formed. Cutting back and thinning out of the branches should be practised at every winter pruning in order to give the tree the required symmetrical arrangement of branches. For trees which tend to become close and compact, thinning out of branches is chiefly needed: for those which tend to become weak and elongated, more cutting back is necessary. By the fifth or sixth year, the framework of the tree should be formed and paying crops produced. The methods of pruning bearing trees vary greatly in various countries. In many, a very severe cutting-back is practised every other year and, as a consequence, the olive bears only on alternate years. The origin of this custom seems to have been due to the olive-fly and scale, which can be fairly well controlled by this means. Trees which arc not pruned at all also tend to bear only every other year and to have small inferior fruit. As the olive bears only on the two-year-old wood, like the peach, annual pruning is necessary for annual crops. The most approved method in California is an annual pruning which consists principally of thinning out from one-third to one-half of the small branches. As much as possible of the removals should be of branches which have borne the preceding year, especially those which have made little new growth. Injured or ill-placed branches are removed and the fruiting surface spread as uniformly over the tree as possible. Vigorous trees should be pruned less than those which are weak and removals made in such a way that light and air reach every part of the bearing wood. Thorough clean cultivation is needed by the olive and is practised as with other orchard-trees in California. The olive will live with less water than most orchard-trees, but for the production of good crops of large fruit an abundant water-supply is necessary- When the moisture is inadequate, the blossoms do not set well and the fruit is small. Most of the paying orchards are irrigated. Frequent and shallow irrigations are unfavorable to the health and bearing of the tree. Heavy winter and spring irrigations followed by thorough summer cultivation are usually sufficient, though a supplementary watering just before blossoming time (March to May) and one when the fruit is almost of full size are useful in many soils and locations. Diseases mid insects. The only serious disease which attacks the olive in California is the "olive- knot." This disease is characterized by numerous knots or tumors on the leaves, twigs, branches and trunk, varying in size from ⅛ inch to 1 or occasionally 2 inches (Figs. 2573, 2574). When badly attacked, the tree is much weakened and, in extreme cases, killed or rendered unprofitable. The disease is infectious and caused by specific bacteria (Bacterium savastanoi). Though found in several widely scattered districts, few orchards have been seriously injured and it seems probable that its spread can be controlled by quarantine. It is most harmful to young trees and in rich moist soils of the warmer districts. Eradication by means similar to those used for pear blight seems possible. A fungous disease of the leaves (Cycloconium oleaginum) occurs, but is not important. Rarely, susceptible varieties are slightly weakened by an unusually heavy attack. Fungous decays of roots and stem have been noted, but do little damage as a rule. Old olive trees in Europe often bear satisfactory crops even after a great part of the interior of the trunk has decayed (Fig. 2575). The black scale (Saissetia oleae) is very injurious to the olive in the moister regions of the coast ranges, in some parts being so prevalent as to prevent the profitable growing of the tree. In the dry summer air of the ulterior the scale is absent or not injurious. The noxious olive-fly and olive-moth of Europe do not exist in California. Harvesting. The stage of maturity at which the olives are harvested depends upon the use that is to be made of them. For green pickles, they should be gathered as soon as or just before they have reached full size and before they show the slightest change of color. Only at this stage is it possible to preserve the clear yellowish green which the consumer demands and which insures the best price. In ripe pickles, the consumer demands a deep uniform shade as nearly black as possible. Different varieties of olives vary considerably in the amount of coloring matter they contain, but in all varieties it develops its full intensity only at full maturity. As the olives on a tree do not all ripen together, it is customary to wait until nearly all have developed a good black color. If gathered too soon, many will bleach to yellow or red in the pickling process; if left top long many will become too soft. Both these difficulties can be over-come to a large extent by modifications in the methods of pickling. When used for oil-making, the quality and quantity of the oil will vary according to the degrees of ripeness of the fruit, when gathered. The maximum quantity is obtained by harvesting the olives when they are completely mature and soft. There is an increase in the percentage of oil afterward, due to a partial drying of the fruit, but no increase in the total quantity of oil. The finest and most highly prized oil is made from olives gathered just before they begin to soften. In gathering olives for any purpose, they must be picked from the tree by hand and all bruising of the fruit avoided. Cloth bags or lined buckets hung over the shoulders of the pickers are used. Knocking the olives off the trees with rods and gathering from the ground is never practised for pickling olives; nor is it advisable for oil olives, as the mechanical injuries to the fruit promote rotting and molding which much depreciate the quality of the oil. Beating the trees also destroys much of the best fruit wood and tends to promote the spread of the olive-knot disease. Where oil olives can be marketed immediately, they may be gathered by means of special rakes with wooden teeth. Pickling olives. When pickles are made, the olives should be cleaned and sized as soon as possible after gathering. The sizing is done by mechanical graders which sort the olives into three or more sizes. The larger sizes are each pickled separately and the smallest used for oil. The grader should be such that the fruit is bruised as little as possible. The cleaning is accomplished by a blower which removes leaves and similar light materials and by running the olives into water which removes the dust. The pickling process consists in removing the bitterness by means of soda or potash lye and water, then hardening and preserving the olives with a solution of common salt. The nature of the lye treatment will depend on the variety, size and degree of ripeness of the fruit. For this reason, each variety and grade should be treated separately. The effect of the lye is partially to destroy the bitterness and to make the skin more pervious to the pickling solutions. Some varieties of olives are extremely bitter or thick-skinned and require two or three times as much lye as other varieties. If too little lye is used, the extraction of the bitterness will be very slow and often incomplete; if too much is used, the olives will become soft, the flavor will be injured and the nutritive value impaired by saponification of some of the oil. Average olives are placed in a solution composed of two ounces of potash lye to one gallon of water. They are left in this solution from four to not more than twelve hours. When the lye has penetrated nearly to the pit as shown by a darkening of the flesh, the olives should be removed to a bath of pure water. With very bitter olives, a second treatment with lye is often necessary. Stronger lye is likely to soften the fruit too much. With very ripe or soft olives, it is necessary to use salt from the beginning in the lye solution. Equal quantities of salt and lye may be used and more time is needed for neutralization owing to the hardening effect of the salt. Some picklers prefer to use a 1 per cent lye for all olives and to repeat the treatment two or three times. The next step is to remove the excess of lye from the olives. If the olives are firm, this is most economically and rapidly accomplished by soaking in pure water which is changed twice a day. If the olives are soft, the water should contain 2 per cent of salt. As soon as no taste of lye remains in the olives, they are placed in a brine composed of four ounces of salt to one gallon of water. This brine is replaced in about two, seven and twenty-one days with brines of six, ten and fourteen ounces to the gallon. This gradual increase of the strength is necessary to prevent shrinkage and shriveling of the olives. Great care should be taken not to allow the olives to come in contact with anything that will injure their flavor. The vats or other receptacles used for pickling should be perfectly clean, odorless, and tasteless. Concrete is the best material, but wooden receptacles thoroughly treated with boiling water and soda until they are sterilized and all taste of the wood removed, may be used. The vats should be provided with a removable wooden grating, fastened 1 or 2 inches from the bottom, and a close-fitting, floating wooden cover to keep all olives submerged. Each vat should be provided at the bottom with a wooden spigot for drawing off the solutions. The thickness of the layer of olives should not be more than 2 feet, or less with soft varieties. In pickling green olives, when a light color is desirable, the fruit should be exposed as little as possible to the air, especially during the extraction of the bitterness. In pickling ripe olives, on the contrary, when a uniform dark color is desired, the action of the air is beneficial. A great improvement in this respect can be obtained by leaving the olives exposed to the air for twenty-four hours when making the various changes of lye and salt solutions. However carefully the processes of pickling are carried out, the olives will keen only for a limited time. They usually remain in good condition for about six months when kept in a strong brine, and the best may last in fair condition for a few months longer. Few olives are good when kept in the ordinary way for twelve months, but by heating them in sealed cans or bottles, they can be kept indefinitely with as great facility as any other food-product. The heating does not injure the flavor and the texture, but, on the contrary, improves them. Olives preserved by heating do not require such strong brine, and it is only necessary to add as much salt as the palate requires. Olive oil. The best oil is made by working the olives as soon as they are gathered, but it is usual to dry them partially first to facilitate crushing and pressing. The drying is accomplished by spreading the fruit in layers not over 3 inches deep on wooden trays which are spread out in a well-aerated shed or loft. The olives must be turned daily and prevented from molding. In cool, moist weather this is very difficult, and artificial driers constructed on the same principles as those for fruit and hops are sometimes used. The heat of these driers should be between 120° and 130° F. Higher temperatures produce rancidity of the oil. Artificial drying requires about forty-eight hours; natural drying one to two weeks. The dried olives may be stored in a cool, dark, dry place for some time before crushing, but the sooner they are used the better the oil; especially when dried by artificial heat. The olives are first passed through a crusher consisting usually of corrugated rollers which disintegrate the flesh without breaking the pits. The crushed mass is then put under a press of moderate power. To facilitate the escape of the oil and water, the crushed olives are placed in layers of 3 to 4 inches, inclosed in strong cloth and separated by gratings. After this pressing, the pulp is thoroughly ground, usually with the pits, in an "edge-runner" mill. The ground pulp is then pressed a second tune. The second pressing requires a very powerful press and very strong cloth to contain the pulp. The first pressing may be omitted when the olives are dried. The liquid which comes from the press contains oil, water and various impurities both solid and dissolved in the water. If allowed to stand, the oil, owing to its light specific gravity, will come to the top and may be skimmed off and freed from floating solid matters by screening. The separation, however, is very slow and imperfect and is facilitated by the process known as "washing." There are various devices for this purpose but they all consist in mixing the press liquids with a stream of pure water with continued gentle agitation. Some of the devices are continuous and the oil rising to the top flows off into the oil vats and the water and impurities escape at the bottom. The oil thus obtained is more or less cloudy owing to the presence of minute particles of solid matter and must be made perfectly bright before it is merchantable. Perfect clarification of the oil may be accomplished by several successive settlings and decantations. The settling vats may be of tin or concrete. Drawing off after a settling of twenty-four to forty-eight hours removes most of the solid matter. The remainder is removed by two or three drawings-off, each after a settling of about a month. Filtration is usually used to hasten clarification. The most commonly used filtering materials are cotton, pure sand and filter paper. Filtering must be practised with moderation as it tends to diminish the flavor. Only 50 per cent to 65 per cent of the oil js recovered by the methods now in use in California. The pulp with the retained oil is wasted or used as pig feed. A somewhat large percentage of the oil can be recovered by means of a centrifugal machine and the troublesome pressing and press cloths done away with. This method, however, has never been adapted to an industrial scale. Pressing is also done away with in the "Acapulco" method by which the oil is extracted by a partial vacuum. This method is said to be used successfully in several mills in Spain and Italy. Varieties. A very large number -of olive varieties have been introduced into California, including the principal varieties of Spain, France and northern Italy. Many of these, especially the Italian varieties, are too small to make acceptable pickles and have been in great part abandoned or grafted over with larger varieties.' Most of the recent plantings have consisted of Mission, Ascolano, Manzanillo and Sevillano, though about ten or twelve varieties are still found in commercial quantities. Short descriptions of the chief of these are given. Mission (Fig. 2576).—The fruit of the common or broad-leaved Mission is typically olive-shaped, slightly oblique and pointed. Its deep color when ripe makes it suitable for ripe pickles. It ripens rather late and does not fruit nor mature well in the cooler sections. It varies in size from small to large according to soil, climate and cultural conditions. The ripe fruit is very bitter but it is firm and easy to pickle. It is one of the best oil olives among the large varieties, both as regards quantity and quality. More than half of the olives of California are of this variety. Ascolano (Fig. 2576).—This variety, the largest of all the olives grown in California, comes from Italy, where it is grown in the province of Umbria. It is regularly ellipsoidal in shape and has a very small pit. It is sometimes called the "white olive of Ascoli" because it has very little color even when perfectly ripe. This is considered a defect for ripe pickles but by proper aeration during pickling, it can be made sufficiently dark and the color has the advantage of being very uniform. It maintains its size under most conditions and bears good crops in all the sections where it has been tried. It contains very little bitterness and requires very moderate lye treatment. Its flesh is somewhat tender and this and its large size make special care and skill necessary in preparing the ripe pickles. Many picklers have failed in this respect, out by the proper use of salt from the beginning and careful use of lye, success is not difficult and the pickles when well made command the highest price. Plantings of this variety have been heavy for several years and limited only by the scarcity of nursery trees. Manzanillo, Number 1 (Fig. 2576).—This olive is of Spanish origin and, as its name indicates, it is apple- shaped. It is deeply colored and bitter when ripe and requires treatment with strong lye, but as it softens easily in pickling great care is needed. It ripens several weeks earlier than the Mission. It is on the average a little larger than the Mission though the largest samples of both varieties do not differ much. Its oil is somewhat inferior to that of Mission both in quantity and quality. Manzanillo, Number 2 is the variety usually pickled in Spain. It is of excellent quality but too small for the Californian market. Sevillano (Fig. 2576).—This is the variety from which the largest "Queen" olives of Spain are made. The largest specimens excel the Ascolano in size but it is less uniform. It is of typical olive-shape. It has a large pit and is deeply colored like the Mission. It is particularly suited for making both green and ripe pickles, but its large size makes special care necessary in the process. It is a good bearer in good, rich soil in warm localities but its range of adaptation seems more limited than that of the Ascolano. Macrocarpa and Polymorpha, which seem to be synonyms, arc very large and suitable for ripe pickles but are liable to a disease causing a spotting or softening of the flesh which much decreases their value. Among other large-fruited varieties which have been tried and which have given good results in some sections are Obliza, Salonica, Regalis, Empeltre, and Columbella. These are not being largely planted now, as they are excelled in most respects by the four preferred varieties. Among smaller varieties which under favorable conditions produce fruit large enough for pickling are the Nevadillo bianco, Oblonga, Pendulina and Uvaria. The Nevadillo (Fig. 2576) especially was planted largely at one time and under suitable conditions is one of the best oil olives. It is, however, sensitive to cold, subject to dry-rot of the fruit and in many sections an unreliable bearer. The Picholine, a variety used in France for "olives farcies" gives excellent fruit in California but has been little planted. The so-called Redding Picholine (Fig. 2576), which was largely planted some years ago under the impression that it was the true French Picholine, is a seedling whose fruit is very small and useless. Frantoio (Fig. 2576) is a type of Italian oil olive which does well in California, but is not profitable, as the fruit is too small for pickling. Literature. See publications of the Agricultural Experiment Station, Berkeley, California, especially Report for 1896, Bulletin Nos. 120, 123, 129, 137, and 158; also Reports of the Horticultural Commission, Sacramento, California, especially the Proceedings of the Olive- Growers' Conventions. Also Bleasdale, "The Olive Tree and Its Products," 1881; Calkins, "Gleanings in Olive-Culture," 1892; Cooper. "A Treatise on Olive- Culture," 1882; Flamant, "A Practical Treatise on Olive-Culture, Oil-making and Olive-pickling." 1887; Lelong, "The Olive in California," 1888; Marvin, "The Olive," 1888. Frederic T. Bioletti. The above text is from the Standard Cyclopedia of Horticulture. It may be out of date, but still contains valuable and interesting information which can be incorporated into the remainder of the article. Click on "Collapse" in the header to hide this text.

This article is about the tree; for its edible fruit, see Olive (fruit); for other uses, see Olive (disambiguation).

"Olive tree" redirects here; for other uses, see The Olive Tree.

? Olive
Olea europaea, Dead Sea, Jordan
Plant Info
Scientific classification
Kingdom: Plantae Division: Magnoliophyta Class: Magnoliopsida Order: Lamiales Family: Oleaceae Genus: Olea Species: O. europaea
Binomial name
Olea europaea L.

19th century illustration

The Olive (Olea europaea) is a species of small tree in the family Oleaceae, native to coastal areas of the eastern Mediterranean region, from Syria and the maritime parts of Asia Minor and northern Iran at the south end of the Caspian Sea. Its fruit, the olive, is of major agricultural importance in the Mediterranean region as the source of olive oil.

Description

The Olive is an evergreen tree or shrub native to the Mediterranean, Asia and parts of Africa. It is short and squat, and rarely exceeds 8-15 meters in height.

The silvery green leaves are oblong in shape, measuring 4-10 cm long and 1-3 cm wide. The trunk is typically gnarled and twisted.

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

The fruit is a small drupe 1-2.5 cm long, thinner-fleshed and smaller in wild plants than in orchard cultivars. Olives are harvested at the green stage or left to ripen to a rich purple color (black olive). Canned black olives may contain chemicals that turn them black artificially.

History

Template:See also The olive is one of the plants most cited in recorded literature. In Homer's Odyssey, Odysseus crawls beneath two shoots of olive that grow from a single stock. The Roman poet, Horace mentions it in reference to his own diet, which he describes as very simple: "As for me, olives, endives, and smooth mallows provide sustenance." Lord Monboddo comments on the olive in 1779 as one of the foods preferred by the ancients and as one of the most perfect foods.

Old trees

Pliny the Elder told of a sacred Greek olive tree that was 1600 years old. Several trees in the Garden of Gethsemane (from the Hebrew words "gat shemanim" or oil press) in Jerusalem are claimed to date back to the time of Jesus. Some Italian olive trees are believed to date back to Roman times, although identifying progenitor trees in ancient sources is difficult.

However, the age of an olive tree in Crete, claimed to be over 2,000 years old, has been determined on the basis of tree ring analysis. Another, on the island of Brijuni (Brioni), Istria in Croatia, a well-known olive tree has been calculated to be about 1,600 years old. It still gives fruit (about 30 kg per year), which is made into top quality olive oil. The olive tree is one of the symbols of Athena, the Greek goddess, and is frequently mentioned in the Bible and the Qur'an.

Cultivation and uses

An example of black olives.

The olive has been cultivated since ancient times as a source of olive oil, fine wood, and olives for consumption. The fruit, naturally bitter, typically subjected to fermentation or cured with lye or brine to make it more palatable.

Green olives and black olives are soaked in a solution of sodium hydroxide and washed thoroughly in water to remove oleuropein, a naturally bitter carbohydrate.

Green olives are allowed to ferment before being packed in a brine solution. American black ("California") olives are not fermented, which is why they taste milder than green olives.

It is not known when olives were first cultivated for harvest. Among the earliest evidence for the domestication of olives comes from the Chalcolithic Period archaeological site of Teleilat Ghassul in what is today modern Jordan.

The plant and its products are frequently referred to in the Bible, the Qur'an and by the earliest recorded poets. Farmers in ancient times believed olive trees would not grow well if planted more than a short distance from the sea; Theophrastus gives 300 stadia (55.6 km) as the limit. Modern experience does not always confirm this, and, though showing a preference for the coast, it has long been grown further inland in some areas with suitable climates, particularly in the southwestern Mediterranean (Iberia, northwest Africa) where winters are milder.

Olive plantation in Andalucia, Spain.

Olives are now cultivated in many regions of the world such as South Africa, Australia, New Zealand, Mediterranean Basin and California. Considerable research has been accumulated supporting the health benefits of consuming olives and olive oil (see external links below for research results).

The olive tree provides leaves, fruit and oil. Olive leaves are used in medicinal teas.

Subspecies

There are at least five natural subspecies distributed over a wide range:

• Olea europaea subsp. europaea (Europe)
• Olea europaea subsp. cuspidata (Iran to China)
• Olea europaea subsp. guanchica (Canaries)
• Olea europaea subsp. maroccana (Morocco)
• Olea europaea subsp. laperrinei (Algeria, Sudan, Niger)

Cultivars

Small Olive Tree

Large Olive Tree

Olive Tree Leaves

Olive Tree Trunk

Olive Flowers

A young olive plant, germinated from a seed

Monumental tree in Apulia Region - Southern Italy

There are thousands of cultivars of the olive. In Italy alone at least three hundred cultivars have been enumerated, but only a few are grown to a large extent. The main Italian cultivars are 'Leccino', 'Frantoio' and 'Carolea'. None of these can be safely identified with ancient descriptions, though it is not unlikely that some of the narrow-leaved cultivars most esteemed may be descendants of the Licinian olive. The Iberian olives are usually cured and eaten, often after being pitted, stuffed (with pickled pimento, onion, or other garnishes) and jarred in fresh brine.

Since many cultivars are self sterile or nearly so, they are generally planted in pairs with a single primary cultivar and a secondary cultivar selected for its ability to fertilize the primary one, for example, 'Frantoio' and 'Leccino'. 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.

Some particularly important cultivars of olive include:

• 'Frantoio' and 'Leccino'. These cultivars are the principal participants in Italian olive oils from Tuscany. Leccino has a mild sweet flavour while Frantoio is fruity with a stronger aftertaste. Due to their highly valued flavour, these cultivars have been migrated and are now grown in other countries.
• 'Arbequina' is a small, brown olive grown in Catalonia, Spain. As well as being used as a table olive, its oil is highly valued.
• 'Empeltre' is a medium sized, black olive grown in Spain. They are used both as a table olive and to produce a high quality olive oil.
• 'Kalamata' is a large, black olive, named after the city of Kalamata, Greece, used as a table olive. These olives are of a smooth and meatlike taste.
• 'Koroneiki' originates from the southern Peloponese, around Kalamata and Mani in Greece. This small olive, though difficult to cultivate, has a high oil yield and produces olive oil of exceptional quality.
• 'Pecholine' or 'picholine' originated in the south of France. It is green, medium size, and elongated. Their flavour is mild and nutty.
• 'Lucques' originated in the south of France (Aude département). They are green, of a large size, and elongated. The stone has an arcuated shape. Their flavour is mild and nutty.
• 'Souri' (Syrian) originated in Lebanon and is widespread in the Levant. It has a high oil yield and exceptionally aromatic flavour.
• 'Nabali' is a Palestinian cultivar also known locally as 'Baladi', which along with 'Souri' and 'Malissi' are considered to produce among the highest quality olive oil in the world.
• 'Barnea' is a modern cultivar bred in Israel to be disease resistant and to produce a generous crop. It is used both for oil and for table olives. The oil has a strong flavour with a hint of green leaf. Barnea is widely grown in Israel and in the southern hemisphere, particularly in Australia and New Zealand.
• 'Maalot' is another modern, disease-resistant, Eastern Mediterranean cultivar derived from the North African 'Chemlali' cultivar. The olive is medium sized, round, has a fruity flavour and is used almost exclusively for oil production.
• 'Mission' originated on the California Missions and is now grown throughout the state. They are black and generally used for table consumption.

Growth and propagation

Olive trees show a marked preference for calcareous soils, flourishing best on limestone slopes and crags, and coastal climate conditions. They tolerate drought well, thanks to their sturdy and extensive root system. Olive trees can be exceptionally long-lived, up to several centuries, and can remain productive for as long, provided they are pruned correctly and regularly.

The olive tree grows very slowly, but over many years the trunk can attain a considerable diameter. A. P. de Candolle recorded one exceeding 10 m in girth. They can possibly reach great age and the trees rarely exceed 15 m in height, and are generally confined to much more limited dimensions by frequent pruning. 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.

The olive is propagated in various ways, but cuttings or layers are generally preferred; the tree roots easily in favourable soil and throws up suckers from the stump when cut down. However, yields from trees grown from suckers or seeds are poor; it must be budded or grafted onto other specimens to do well (Lewington and Parker, 114). Branches of various thickness are cut into lengths of about 1 m and, planted deeply in manured ground, soon vegetate; shorter pieces are sometimes laid horizontally in shallow trenches, when, covered with a few centimetres of soil, they rapidly throw up sucker-like shoots. In Greece, grafting the cultivated tree on the wild form is a common practice. In Italy, embryonic buds, which form small swellings on the stems, are carefully excised and planted beneath the surface, where they grow readily, their buds soon forming a vigorous shoot.

Occasionally the larger boughs are marched, and young trees thus soon obtained. The olive is also sometimes raised from seed, the oily pericarp being first softened by slight rotting, or soaking in hot water or in an alkaline solution, to facilitate germination.

Where the olive is carefully cultivated, as in Languedoc and Provence, the trees are regularly pruned. The pruning preserves the flower-bearing shoots of the preceding year, while keeping the tree low enough to allow the easy gathering of the fruit. The spaces between the trees are regularly fertilized. The crop from old trees is sometimes enormous, but they seldom bear well two years in succession, and in many instances a large harvest can only be reckoned upon every sixth or seventh season.

A calcareous soil, however dry or poor, seems best adapted to its healthy development, though the tree will grow in any light soil, and even on clay if well drained; but, as remarked by Pliny, the plant is more liable to disease on rich soils, and the oil is inferior to the produce of the poorer and more rocky ground.

Fruit harvest and processing

Most olives today are harvested by shaking the boughs or the whole tree. Another method involves standing on a ladder and "milking" the olives into a sack tied around the harvester's waist. Using olives found lying on the ground can result in poor quality oil. In southern Europe the olive harvest is in the winter months, continuing for several weeks, but the time varies in each country, and also with the season and the kinds cultivated. A device called the oli-net wraps around the trunk of the tree and opens to form an umbrella like catcher to catch fruit that is picked. Workers can then harvest the fruit without the weight of the load around their neck. Another device, the oliviera, is an electronic tool that connects to a battery. The oliviera has large tongs that are spun around quickly, removing fruit from the tree. This method is used for olive oil variety olives. Table olive varieties are more difficult to harvest, as workers must take caution not to damage the fruit in any way. Picking baskets that hang around the worker's neck are used.

The amount of oil contained in the fruit differs greatly in the various cultivars; the pericarp is usually 60-70% oil. Typical yields are 1.5-2.2 kg of oil per tree per year.

Olive Oil History

Homer called it "liquid gold." In ancient Greece, athletes ritually rubbed it all over their body. Drops of it seeped into the bones of dead saints and martyrs through holes in their tombs. Olive oil has been more than mere food to the peoples of the Mediterranean: it has been medicinal, magical, an endless source of fascination and wonder and the fountain of great wealth and power. The olive tree, symbol of abundance, glory and peace, gave its leafy branches to crown the victorious in friendly games and bloody war, and the oil of its fruit has anointed the noblest of heads throughout history. Olive crowns and olive branches, emblems of benediction and purifiation, were ritually offered to deities and powerful figures: some were even found in Tutankhamen's tomb.

Traditional fermentation

Olives freshly picked from the tree contain phenolic compounds and a unique glycoside, oleuropein, which makes the fruit unpalatable for immediate consumption. There are many ways of processing olives for table use. Traditional methods use the natural microflora on the fruit and procedures which select for those that bring about fermentation of the fruit. This fermentation leads to three important outcomes: the leaching out and breakdown of oleuropein and phenolic compounds; the creation of lactic acid, which is a natural preservative; and a complex of flavoursome fermentation products. The result is a product which will store with or without refrigeration.

One basic fermentation method is to get food grade containers, which may include plastic containers from companies which trade in olives and preserved vine leaves. Many bakeries also recycle food grade plastic containers which are well sized for olive fermentation; they are 10 to 20 litres in capacity. Freshly picked olives are often sold at markets in 10 kg trays. Olives should be selected for their firmness if green and general good condition. Olives can be used green, ripe green (which is a yellower shade of green, or green with hints of color), through to full purple black ripeness. The olives are soaked in water to wash them, and drained. 7 litres (which is 7 kg) of room temperature water is added to the fermentation container, and 800 g of sea salt, and one cup (300g) of white vinegar (white wine or cider vinegar). The salt is dissolved to create a 10% solution (the 800 g of salt is in a 8 kg mixture of salt and water and vinegar). Each olive is given a single deep slit with a small knife (if small), or up to three slits per fruit (if large, eg 60 fruit per kg). If 10 kg of olives are added to the 10% salt solution, the ultimate salinity after some weeks will be around 5 to 6% once the water in the olives moves into solution and the salt moves into the olives. The olives are weighed down with an inert object such as a plate so they are fully immersed and lightly sealed in their container. The light sealing is to allow the gases of fermentation to escape. It is also possible to make a plastic bag partially filled with water, and lay this over the top as a venting lid which also provides a good seal. The exclusion of oxygen is useful but not as critical as when grapes are fermented to produce wine. The olives can be tasted at any time as the bitter compounds are not poisonous, and oleuropein is a useful antioxidant in the human diet.

The olives are edible within 2 weeks to a month, but can be left to cure for up to three months. Green olives will usually be firmer in texture after curing than black olives. Olives can be flavored by soaking them in various marinades, or removing the pit and stuffing them. Herbs, spices, olive oil, feta, capsicum (pimento), chili, lemon zest, lemon juice, garlic cloves, wine, vinegar, juniper berries, and anchovies are popular flavorings. Sometimes the olives are lightly cracked with a hammer or a stone to trigger fermentation. This method of curing adds a slightly bitter taste.

Pests and diseases

A fungus Cycloconium oleaginum can infect the trees for several successive seasons, causing great damage to plantations. A species of bacterium, Pseudomonas savastanoi pv. oleae induces tumour growth in the shoots, and certain lepidopterous caterpillars feed on the leaves and flowers, while the main damage is made by the olive-fly attacks to the fruit. In France and north-central Italy olives suffer occasionally from frost. Gales and long-continued rains during the gathering season also cause damage. Another pest which spreads through olive trees is the black scale bug. Black scale is a small black beetle that resembles a small black spot. They attach themselves firmly to olive trees and reduce the quality of the fruit. The main predator of black scale is wasps.

Economy

Olive output in 2005

Production

Olive is the most extensively cultivated fruit crop in the world. Its cultivation areas has tripled in the past 44 years, passing from 2.6 to 8.5 million of hectares.

The first ten countries of production, as per FAO, all located in the Mediterranean region, represent together 95% of the world production of olives.

Main countries of production (Year 2003)

Rank	Country/Region	Production (in tons)	Cultivated area (in hectares)	Yield (q/Ha)
—	World	17,317,089	8,597,064	20.1
1	Spain	6,160,100	2,400,000	25.7
2	Italy	3,149,830	1,140,685	27.6
3	Greece	2,400,000	765,000	31.4
4	Turkey	1,800,000	594,000	30.3
5	Syria	998,988	498,981	20.0
6	Tunisia	500,000	1,500,000	3.3
7	Morocco	470,000	550,000	8.5
8	Egypt	318,339	49,888	63.8
9	Algeria	300,000	178,000	16.9
10	Portugal	280,000	430,000	6.5
11	Lebanon	180,000	230,000	4.5

Olive as an invasive weed

Since its first domestication, Olea europaea has been spreading back to the wild from planted groves. Its original wild populations in southern Europe have been largely swamped by feral plants.

In some other parts of the world where it has been introduced, most notably South Australia, the Olive has become a major woody weed that displaces native vegetation. Its seeds are spread by the introduced Red Fox and by many bird species including the European Starling and the native Emu into woodlands where they germinate and eventually form a dense canopy that prevents regeneration of native trees.

See also

• Oil-tree
• Olive (fruit)
• Phytonutrient
• Polyphenol antioxidant

External links

• The Olive Tree World
• Olive germplasm
• Plants for a Future: Olea europaea
• International Olive Oil Council Includes studies on health benefits
• The history and gastronomy of the olive and olive oil in Spain
• Greek Olives and Olive Oil: History, cultivation, production and marketing
• How to pickle olives
• Pickling Olives the Mediterranean Way