Olea europaea subsp. europaea (European olive)
- Summary of Invasiveness
- Taxonomic Tree
- Notes on Taxonomy and Nomenclature
- Distribution Table
- History of Introduction and Spread
- Risk of Introduction
- Habitat List
- Biology and Ecology
- Latitude/Altitude Ranges
- Natural enemies
- Notes on Natural Enemies
- Means of Movement and Dispersal
- Impact Summary
- Environmental Impact
- Risk and Impact Factors
- Similarities to Other Species/Conditions
- Prevention and Control
- Links to Websites
- Distribution Maps
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PicturesTop of page
IdentityTop of page
Preferred Scientific Name
- Olea europaea subsp. europaea L.
Preferred Common Name
- European olive
Other Scientific Names
- Olea alba Lam. ex Steud.
- Olea amygdalina Gouan
- Olea angulosa Gouan
- Olea argentata Clemente ex Steud.
- Olea atrorubens Gouan
- Olea bifera Raf.
- Olea brevifolia Raf.
- Olea cajetana Petagna
- Olea cayana Raf.
- Olea communis Steud.
- Olea communis Steud.
- Olea craniomorpha Gouan
- Olea ferruginea Wall. ex Aitch.
- Olea gallica Mill.
- Olea hispanica Mill.
- Olea lancifolia Moench
- Olea longifolia Steud.
- Olea lorentii Hochst.
- Olea obliqua Steud.
- Olea oblonga Gouan
- Olea odorata Rozier ex Roem. & Schult.
- Olea officinarum Crantz
- Olea oleaster Hoffmanns. & Link
- Olea pallida Salisb.
- Olea polymorpha Risso ex Schult.
- Olea praecox Gouan
- Olea racemosa Gouan
- Olea regia Rozier ex Roem. & Schult.
- Olea sativa Weston
- Olea sphaerica Gouan
- Olea sylvestris Mill.
- Olea variegata Gouan
- Olea variegata Gouan
- Olea viridula Gouan
- Phillyrea lorentii Walp.
International Common Names
- English: olive tree
- Spanish: aceituna; oliva; olivo
- French: olivier
- Arabic: az-zeitoun
- Chinese: mu xi lan
- Portuguese: oliveira
Local Common Names
- French Polynesia: orive
- Germany: Oelbaum; Olivenbaum
- Israel: zayit
- Netherlands: Olijfboom
- Sweden: olivtraed
- USA/Hawaii: ‘oliwa; ‘oliwa haole
Summary of InvasivenessTop of page
O. europaea subsp. europaea, the cultivated olive, is native to Africa and temperate Asia as well as southern Europe. It was introduced into Australia and Hawaii, USA for cultivation and production of its fruits and has since naturalized. This species can form dense monocultures which can increase the likelihood of fires (due to the high levels of oil in the foliage and wood) and decrease the biodiversity of an area by shading and competing with native species. Although less aggressive than the closely related subspecies O. europaea subsp. cuspidata, it has the potential to become invasive and in Australia it is declared an environmental weed. A PIER (2016) risk assessment for the Pacific region however, gives this taxa a low score of 3.
Taxonomic TreeTop of page
- Domain: Eukaryota
- Kingdom: Plantae
- Phylum: Spermatophyta
- Subphylum: Angiospermae
- Class: Dicotyledonae
- Order: Oleales
- Family: Oleaceae
- Genus: Olea
- Species: Olea europaea subsp. europaea
Notes on Taxonomy and NomenclatureTop of page
The cultivated olive, Olea europaea, belongs to Oleaceae, a medium-sized family of approximately 25 genera and 688 species distributed throughout temperate and tropical regions of the world (The Plant List, 2013). Plants in this family are primarily trees and bushes along with a number of vines, many of which produce essential oils in their flowers or fruits (Janick and Paull, 2008).
The genus Olea contains 35 accepted species including O. europaea. There are many and differing opinions as to nomenclature and hierarchies within both the genus and the species. Among the terms most commonly associated with the cultivated olive, either on a subspecies or variety level, are sativa and communis. A thorough revision of the genus (Green, 2002) proposes a broad O. europaea complex of six subspecies, which extends through Macronesia, Mediterranean, African and Asian regions. Within this complex, the cultivated olive is designated as O. europaea subsp. europaea.
However, there are disagreements with this revision. ITIS (2016) accepts only two subspecies – O. europaea subsp. europaea L. and O. europaea subsp. cuspidata (Wall. ex G. Don) Cif., rejecting the taxa O. africana Mill., O. chrysophylla Lam., O. europaea subsp. africana (Mill.) P. Green, O. ferruginea Royle, O. verrucosa (Willd.) Link. as pseudonyms of O. europaea subsp. cuspidata. In contrast to this, The Plant List (2013) and ISSG (2016) accept five subspecies with different distributions. These include O. europaea subsp. cerasiformis G.Kunkel & Sunding, native to Madeira, O. europaea subsp. cuspidata (Wall. & G.Don) Cif., native to eastern Africa to southern Asia, O. europaea subsp. guanchica P.Vargas et al., native to the Canary Islands, O. europaea subsp. laperrinei (Batt. & Trab.) Cif., native to Sahara and O. europaea subsp. maroccana (Greuter & Burdet) P.Vargas et al., native to Morocco.
Closely related to the cultivated olive is the wild type, generally referred to oleaster or sylvestris. The wild olive is characterized by shrubby growth, smaller leaves and smaller fruit than the cultivated olive. Hybridization between cultivated and wild populations has played an important role in the evolution of olive cultivars (Janick and Paull, 2008). Although self-incompatibility is the norm in olive cultivars, cases of self-fertility are known.
DescriptionTop of page
The olive is a long-lived evergreen tree. Its dimensions and shape vary with climatic conditions, soil fertility, cultivar and cultural practices. Trees growing in the wild exhibit a shrub habit of growth and can reach a height of 10 m. Although when pruned, cultivated olive could reach 15 m. It is able to develop suckers and roots from temporary buds generated by neoplasm formation in the base of the trunk just below the soil surface. These formations are known as 'ovules' and are of considerable importance in conserving the tree as they continue to form and grow as the tree becomes old. The root system is extensive; depth and lateral spread of the root system depends on soil type and depth, aeration and water content.
Seedlings have taproots, which develop downwards, but after first growth of the tree a new adventitious root system develops which replaces the deeper taproots. Trunk usually simple and 1 or 2 m tall, solid, with clearly defined several main branches, which form the canopy of the tree. The leaves are opposite, elliptical, oblong or lanceolate, dark green on the upper side, but silvery on the underside. The inflorescences or flower cluster are formed in the axils of leaves on the previous year's shoots. The number of flowers per inflorescence will vary from 10 to 40 depending upon the cultivar, but they generally set only one fruit per cluster (Bongi and Palliotti, 1994). Only a few cultivars with small fruits (for example, cvs ‘Koroneiki’ and ‘Arbequina’) may set more than three fruits per panicle. The flowers are small, white, fragrant and perfect, consisting of four sepals, four petals, two stamens and two carpels. The calyx has four shallow divisions and is persistent. The corolla to which the petals are attached is three times larger than the calyx and it has four round oval lobes. The two stamens, which lie over the corolla, have short filaments, and the anthers have two lobes. The ovary is unattached, and has two compartments, each containing two anatropic ovules. The style is short and the stigma is extended and forked. Olives are wind pollinated, thus flowering during rain, high temperatures and dry wind conditions are deleterious to good fruit set (Griggs et al., 1975). Mature olive trees produce huge numbers of flowers, but the fruit set is normally below 5% (Lavee, 1986; Martin et al., 1994). Most olive orchards are set in a monocultivar culture. However, they benefit greatly from cross-pollination (Lavee, 1986) in case of geographical isolation (Camposeo et al., 2012).
The fruit is fleshy, elliptical drupe with a stone. Its shape varies with the variety but is normally oval-shaped. When ripe, the olive is brownish-black in colour. The endocarp (or stone) is long, pointed at the apex and very hard. It is divided into two unequal compartments and contains one seed, which has oily albumen. The epicarp remains firmly attached to the mesocarp (or pulp) and is fleshy when ripe. The epicarp and mesocarp contain the olive oil and form the edible part of the fruit. At maturity the fruit contains 10-35% oil, depending on the cultivar.
DistributionTop of page
The European olive tree (O. europaea subsp. europaea) was one of the first cultivated by Mediterranean civilisations some 6000 years ago and is thought to have originated in Asia Minor (Syria and Palestine). Early civilisations of the Mediterranean basin depended on several temperate fruit and nut products such as grapes, olives, figs, almonds, dates and carobs. This area remains active both in the consumption and commerce of these crops. Olive trees were distributed throughout the Mediterranean basin by the Romans and the Arabs. In the 18-19th centuries it was introduced into South and North America, Australia, South Africa and, during the last 30 years, into China (Rugini and Lavee, 1992). Today about 97% of the world supply of olives is produced in Spain, Italy, Greece, Portugal, Turkey, Tunisia, Morocco, Syria, Algeria, France, former Yugoslavia, Jordan, Cyprus, Israel, Libya and Egypt. The remainder is produced in Argentina, USA, Chile, Peru, Mexico, Australia, South Africa and Japan. It is grown between 30 and 45° latitude, both in the northern and southern hemispheres, in areas below sea level in the Jordan Valley, Israel, and areas up to 2000 m high in Argentina. Wild olives (O. europaea subsp. oleaster) occur in many places around the Mediterranean basin.
O. europaea subsp. europaea is native to parts of Africa, temperate Asia and Europe. It has been intentionally introduced into a number of countries outside of its native range for cultivation. However, it is reported to have become invasive Australia, New Zealand and Hawaii, USA (USDA-ARS, 2016).
Records of O. europaea in Africa, outside of the Mediterannean zone are likely to represent the subspecies O. europaea subsp. cuspidata. Unlike the temperate species O. europaea subsp. europaea, O. europaea subsp. cuspidata is distinct and can reproduce in tropical environments.
Distribution TableTop of page
The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.
|Continent/Country/Region||Distribution||Last Reported||Origin||First Reported||Invasive||Planted||Reference||Notes|
|Afghanistan||Present||Introduced||IRIN, 2016||Subspecies not specified|
|Iran||Present||Introduced||International Olive Council, 2016||Subspecies not specified|
|Israel||Present||Native||USDA-ARS, 2016||O. europaea subsp europaea|
|Jordan||Present||Native||USDA-ARS, 2016||O. europaea subsp europaea|
|Saudi Arabia||Present||Native||USDA-ARS, 2016||Subspecies not specified|
|Singapore||Present||Introduced||PIER, 2016||Subspecies not specified|
|Taiwan||Present||Introduced||PIER, 2016||Subspecies not specified|
|Turkey||Present||Native||USDA-ARS, 2016||O. europaea subsp europaea|
|Yemen||Present||Native||USDA-ARS, 2016||Subspecies not specified|
|Algeria||Present||Native||USDA-ARS, 2016||O. europaea subsp europaea|
|Libya||Present||Native||USDA-ARS, 2016||O. europaea subsp europaea|
|Morocco||Present||Native||USDA-ARS, 2016||O. europaea subsp europaea|
|-Canary Islands||Present||Native||USDA-ARS, 2016||O. europaea subsp europaea|
|Tunisia||Present||Native||USDA-ARS, 2016||O. europaea subsp europaea|
|USA||Present||Present based on regional distribution.|
|-Hawaii||Present||Introduced||Invasive||USDA-ARS, 2016||O. europaea subsp. europaea|
|Bolivia||Present||Introduced||Encyclopedia of the Nations, 2016||Subspecies not specified|
|Chile||Present||Introduced||PIER, 2016||Subspecies not specified|
|Ecuador||Present||Introduced||PIER, 2016||Subspecies not specified|
|Albania||Present||Native||USDA-ARS, 2016||O. europaea subsp europaea|
|Cyprus||Present||Native||USDA-ARS, 2016||O. europaea subsp europaea|
|France||Present||Native||USDA-ARS, 2016||O. europaea subsp europaea|
|Greece||Present||Native||USDA-ARS, 2016||O. europaea subsp europaea|
|Italy||Present||Native||USDA-ARS, 2016||O. europaea subsp europaea|
|Portugal||Present||Native||USDA-ARS, 2016||O. europaea subsp europaea|
|-Madeira||Present||Native||USDA-ARS, 2016||O. europaea subsp europaea|
|Spain||Present||Native||USDA-ARS, 2016||O. europaea subsp europaea|
|Yugoslavia (former)||Present||Native||USDA-ARS, 2016||O. europaea subsp europaea|
|Australia||Present||Introduced||Invasive||USDA-ARS, 2016||O. europaea subsp europaea|
|-New South Wales||Present||Introduced||Invasive||Queensland Government, 2016||O. europaea subsp europaea recorded as an environmental weed|
|-Queensland||Present||Introduced||Invasive||Queensland Government, 2016||O. europaea subsp europaea recorded as an environmental weed|
|-South Australia||Present||Introduced||Invasive||Queensland Government, 2016||O. europaea subsp europaea recorded as an environmental weed|
|-Victoria||Present||Introduced||Invasive||Queensland Government, 2016||O. europaea subsp europaea recorded as a significant environmental weed|
|-Western Australia||Present||Introduced||Invasive||Queensland Government, 2016||O. europaea subsp europaea recorded as an environmental weed|
|French Polynesia||Present||Introduced||PIER, 2016||Subspecies not specified|
|Guam||Present||Introduced||PIER, 2016||Subspecies not specified|
|New Zealand||Present only in captivity/cultivation||Introduced||Invasive||Webb et al., 1988||Subspecies not specified|
|Tonga||Present||Introduced||PIER, 2016||Subspecies not specified|
History of Introduction and SpreadTop of page
Details of the movement of olives (species of Olea) can be found in International Olive Council (2015; 2016c) and Cape Olive Route (2016). This however, does not specify the subspecies involved.
O. europaea subsp. europaea was introduced and has since naturalized on the islands of Maui and Hawaii (Starr et al., 2003). On Hawaii, Wagner et al. (1999) say that this subspecies is ‘apparently spreading rapidly’, but on Maui plants are only occasionally scattered. Starr et al. (2003) stress that although this subspecies is known to spread in Hawaii, it does not seem to be as aggressive or widely planted as O. europaea subsp. cuspidata.
A study by Besnard et al. (2007) investigated the likely origins of both O. europaea subsp. europaea (cultivated) and O. europaea subsp. cuspidata (wild) in Australia and Hawaii, using eight nuclear DNA microsatellites, plastid DNA markers and ITS-1 sequences. They found that east Australian and Hawaiian populations of O. europaea subsp. cuspidata originated in southern Africa, whilst South Australian populations of O. europaea subsp. europaea were mostly derived from western or central Mediterranean cultivars.
Where stated, records in the Distribution Table represent O. europaea subsp. europaea. Other records represent O. europaea and the specific subspecies is not provided.
Risk of IntroductionTop of page
As an attractive crop, O. europaea subsp. europaea has been intentionally introduced into a number of countries. It is likely that it will continue to be introduced into new countries and grown as a crop where it is likely to naturalize.
HabitatTop of page
O. europaea subsp. europaea is often found in semi-arid to sub-humid warm-temperate regions, usually with winter-dominant rainfall and hot, relatively dry summers and can occur on a wide range of soils (Parsons and Cuthbertson, 1992). As an escapee from cultivation, it is often found in recreational parklands soils (Parsons and Cuthbertson, 1992) but is also found in grassland, woodland and riparian habitats (PIER, 2016). In its native range, this species grows in woods, scrub and dry rocky places up to 3000 m elevation. The growth form ranges from stunted shrubs to tall trees (PIER, 2016).
Habitat ListTop of page
|Terrestrial – Managed||Cultivated / agricultural land||Present, no further details|
|Rail / roadsides||Present, no further details|
|Terrestrial ‑ Natural / Semi-natural||Natural forests||Present, no further details|
|Natural grasslands||Present, no further details||Harmful (pest or invasive)|
|Natural grasslands||Present, no further details||Natural|
|Natural grasslands||Present, no further details||Productive/non-natural|
Biology and EcologyTop of page
Growth and Development
The annual development cycle of the olive tree is closely linked to the climatic conditions of the growing area, which is normally a Mediterranean type climate (Pansiot and Rebour, 1960). In the Northern Hemisphere, vegetative growth starts in the spring. Both apical buds and a limited number of lateral buds, which developed in the previous seasons, will start to grow. Temperatures above 12°C are needed to re-induce growth in the spring. The time of flowering is influenced by photoperiod and temperature, but it typically takes place in spring on branch segments formed during the previous season, with 50-80% of leaf axils developing inflorescences (van der Vossen et al., 2007). Most cultivars of O. europaea subsp. europaea need a period of vernalisation for 6-11 weeks below 9°C which ends 40-60 days before anthesis.The initial elongation growth is rapid, particularly in the warmer growing regions. At temperatures above 30°C in mid-summer (mid-July), the vegetative growth rate drops. When there is enough moisture in the soil or under irrigated conditions, a short second period of growth could occur in the autumn with the reduction in daily temperatures. Thus, different types of growth curves of olive trees have been recorded in accordance with the thermal conditions in the summer. In most regions the bearing olive tree has a double peak growth curve (Lavee, 1996). O. europaea subsp. europaea is strong biennial bearer and a heavy fruit load in one year inhibits adequate shoot extension necessary for the following year’s bearing wood and vice versa. In non-bearing trees a continuous but uneven flush of growth takes place along the whole March-October period (Rallo et al., 1994).
The reproductive process leading to spring flowering starts in the preceding summers. The young buds present in the axial of each leaf on sprouts born in spring are undifferentiated. In summer, environmental factors interact with the tree physiology to start the floral induction process (Rallo and Martin, 1991). Once induction is under way, floral initiation only occurs by the end of autumn, after which flower parts form. Eventually, these can be seen with a microscope. The buds not induced become vegetative buds. Unlike deciduous fruits with a short induction-to-initiation cycle, induction in olive may occur as early as July or about 6 weeks after full bloom, whereas initiation is not easily seen until 8 months later in February. Floral differentiation takes place between late December and bloom in May-June when the formation of each flower part occurs in the inflorescence. The pollination of the olive is carried out mainly by wind.
Growth and fruit development in olive also depends on climate, beginning in September and normally ending in November. Olives are picked late in autumn or winter, as the oil content and fruit characteristics change with ripening. Environmental variability may be more important than genetic variability for several traits, including oil content and quality (Bongi and Palliotti, 1994). The chemical components (for example, polyphenols, aliphatic alcohols, triterpenic alcohols, sterols and fatty acids) that determine oil quality vary according to cultivar and year of cultivation. Rainfall is one of the predominant factors affecting oil quality. Irrigation may also affect the variability in oil quality (Uceda and Hermoso, 1997).
A chromosome number of 23 (2n = 46) has been recorded for O. europaea subsp. europaea. Besnard et al. (2007) found strong evidence for hybridization between O. europaea subsp. europaea and O. europaea subsp. cuspidata in early introduction sites in Australia, both in New South Wales and South Australia. It is thought that this may have helped reduce the negative effects due to a loss of genetic diversity and also helped populations adapt better to new environments.
Pollination of the olive is carried out mainly by wind. Some olive cultivars are self-incompatible and, thus, cross-pollination is obligatory (Lavee, 1986). Despite optimal conditions of pollination and initial fruit set, only 1-5% of the flowers will develop into ripe fruit due to severe early (up to 50%) and late physiological fruit abscission, water stress, diseases and pests (van der Vossen et al., 2007). Fruit development takes 6.5-7 months from anthesis to harvesting, the last 20-40 days being essential for oil formation in the mesocarp. Seeds germinate within 25-50 days of sowing but seed viability is generally low, so that the majority of cultivated trees are grown from clonal cultivars (van der Vossen et al., 2007). Commercially, olives are propagated primarily by cuttings, truncheons or by budding seedling rootstocks. The propagation methods used vary with the environmental conditions of the country or region in which the crop is grown. Since the olive tree easily develops new roots from its semi-ligneous tissue, cuttings are normally taken from one-year-old branches near the bottom of selected superior trees. The olive trees propagated by rooting semi-hardwood cuttings come into bearing within three to four years of planting. This method is most efficient and economical and reduces the heterogeneity of an olive grove (Brousse, 1991).
According to Van der Vossen et al. (2007) the commercial lifespan of an olive tree is 50 years, but individual trees can become very old (hundreds of years).
O. europaea subsp. europaea thrives best in places with a Mediterranean climate with wet winters and hot, dry summers such as California, South Africa, Australia and other places around the world. The crop requires an average daily temperature between 15-20°C for adequate growth and development. However, frost in spring can damage young shoots and flowers and in late autumn can damage the ripening fruits (van der Vossen et al., 2007). Trees are frost-hardy in winter and can tolerate -8 to -12°C. It has been reported that optimum temperatures for shoot growth and flowering are 18-22°C and that temperatures above 30°C in spring can damage flowers (van der Vossen et al., 2007). It is possible for trees to withstand much higher temperatures during the summer.
This species can grow on a wide variety of soils but perform best on well-drained, well-aerated deep soils containing adequate organic matter and well supplied with available nutrients. However, normally trees will grow on rocky hillsides with poor soils. Saline or alkaline soils are tolerated, as well as those with a high lime content. The shallow root system is relatively shallow and will not tolerate waterlogged soils. Soils of pH 5-8 are tolerated, but the most favourable is pH 5.5-7.5. It grows well between latitudes of 30 and 45°, both in the northern and southern hemispheres and from sea-level up to 1200-2000 m altitude (Civantos, 1998).
O. europaea subsp. europaea is considered a drought-resistant species because it thrives in areas where water stress is frequent (Mediterranean climate). It has been postulated that the minimum water requirement for olive is 500 mm of annual rainfall to obtain good crops, mainly during flowering and fruit setting in late spring and again in the summer as the fruit size increases (Tous, 1990). High atmospheric humidity is not beneficial for the olive tree because it facilitates the development of diseases.
ClimateTop of page
|Cf - Warm temperate climate, wet all year||Tolerated||Warm average temp. > 10°C, Cold average temp. > 0°C, wet all year|
|Cs - Warm temperate climate with dry summer||Preferred||Warm average temp. > 10°C, Cold average temp. > 0°C, dry summers|
|Ds - Continental climate with dry summer||Tolerated||Continental climate with dry summer (Warm average temp. > 10°C, coldest month < 0°C, dry summers)|
Latitude/Altitude RangesTop of page
|Latitude North (°N)||Latitude South (°S)||Altitude Lower (m)||Altitude Upper (m)|
RainfallTop of page
|Parameter||Lower limit||Upper limit||Description|
|Mean annual rainfall||500||800||mm; lower/upper limits|
Natural enemiesTop of page
Notes on Natural EnemiesTop of page
In Greece, its native range, birds can be a major source of fruit loss and will dispersing seeds to new locations (Bigler and Delucchi, 1981; Spenneman and Allen, 2000b).
In Australia, the Australian native olive lace bug (Frogattia olivinia) has been reported as a pest on this subspecies (Cuneo and Leishman, 2006).
A large list of serious pests and diseases which can damage O. europaea subsp europaea trees or their fruit is available.
Means of Movement and DispersalTop of page
Fruits of O. europaea subsp. europaea which fall from trees could disperse locally and germinate to form new plants.
Frugivorous birds are a major vector for dispersal of seeds (Spenneman and Allen, 2000b). A study by Perea and Gutiérrez-Galán (2016) suggested that Columba palumbus (pigeon) play an important part in seed dispersal and that the rate of germination was increased after injestion. It has been suggested that in Australia, sheep, cattle, rabbits and mice may also aid in seed dispersal, although smaller birds and mammals are unlikely to disperse seeds very far from the parent plants (Spenneman and Allen, 2000b).
O. europaea subsp. europaea is likely to be intentionally introduced into countries for they are a lucrative crop and the plants themselves make attractive and unusual garden or landscape specimens.
Impact SummaryTop of page
|Environment (generally)||Positive and negative|
ImpactTop of page
Published reports often confound impacts of O. europaea subsp. europaea and those of O. europaea subsp. cuspidata. For example, several Australian reports do not always clarify which subspecies is being referred to in the many cases they report both in Australia and elsewhere. Spennemann and Allen (2000a), however, stress that ‘As long as there is an olive industry, either at a commercial or a cottage level, there will be a threat of olives becoming a woody weed with a major impact on remnant bushland.’
Environmental ImpactTop of page
Invasions of O. europaea subsp. europaea may increase the fire hazard of dry woodland environments since it is an inflammable species with a high oil content (ISSG, 2016).
Impact on Biodiversity
Invasion of O. europaea subsp. europaea in South Australia led to a reduction in native species richness and abundance and also altered the canopy structure a woodland (Spenneman and Allen, 2000a). The reduction in light infiltration brought about by the dense canopy of O. europaea subsp. europaea prevents the regeneration of native species and decreases biodiversity in an area. O. europaea subsp. europaea was found to have a significant impact on grey box (Eucalyptus microcarpa) woodlands, areas of conservation significance and were also found to have an impact on golden wattle (Acacia pycnantha) and sticky hop-bush (Dodonaea viscose) (Crossman, 2002).
Risk and Impact FactorsTop of page Invasiveness
- Invasive in its native range
- Proved invasive outside its native range
- Has a broad native range
- Abundant in its native range
- Benefits from human association (i.e. it is a human commensal)
- Long lived
- Reproduces asexually
- Has high genetic variability
- Ecosystem change/ habitat alteration
- Reduced amenity values
- Reduced native biodiversity
- Competition - monopolizing resources
- Competition - shading
- Competition - smothering
- Highly likely to be transported internationally deliberately
- Difficult/costly to control
UsesTop of page
O. europaea subsp. europaea has, for hundreds of years, been the source of olive oil, an essential part of what has become known as the Mediterranean diet. As such this species has been introduced widely around the world where it is grown either as a crop or as ornamental plants. The approximately 2000 cultivars grown as crops can be divided into three groups: cultivars for oil, table olives and for the dual-purpose of oil and table olives. In 2014/15 the world production of olive oil for the 2014/15 crop year was provisionally assessed at 2,444,000 t, down by 25% from 2013/14 (International Olive Council, 2015). For table olives the estimated (projected) total world production was 2,470,500 t in 2014/15 (International Olive Council, 2016b).
Olive fruits are used for two main purposes: table olives and olive oil. The Mediterranean countries have a multitude of typical dishes in which olives, olive oil or a combination of the two, are basic ingredients. This distinctive cuisine is the culinary expression of the increasingly more widespread and popular 'Mediterranean diet'. One of its main characteristics is that an important part of the fats consumed comes from olive oil, and abundant cereals, vegetables and pulses, with their high fibre content, take the place of animal fat (Civantos, 1998).
Table olives are popular as part of the Mediterranean gastronomy and more recently an integral part of the take away pizza market. The latter has been a major market for preserved olives in the USA. To make olives edible fermentation, salt treatment or drying is needed to remove the bitterness due to polyphenolic compounds, in particular 'oleuropein'. Olive fruits are rich in oil and therefore high in energy. They are a good source of protein and b-carotene and contain other useful nutrients such as sugars, vitamins B, C and E, iron and other minerals (calcium and potassium) and nutraceutical compounds (Boskou, 2015a). Olives are a feature of many of the dishes prepared in the producer areas. They impart taste and colour to salads, stuffing, gravy and sauces; they are used as a garnish for an endless array of foods and drinks, as well as a condiment and appetiser. The multitude of styles: green, turning colour, black, stuffed with anchovies, pimiento, almonds, in pastes with other ingredients, bruised and split, offer a whole range of culinary opportunities. Moreover, in southern Italy there are so-called 'sweet olives' which come from two or three cultivars bearing fruits that sweeten naturally, without any treatment after harvesting (Boskou, 2015b).
Olive oil is obtained by pressing or centrifuging the crushed fruit including the seed. All olive oils obtained from olives are classified as Virgin Olive Oils with the highest quality being 'extra virgin olive oil'. This category is high in monounsaturated fatty acid (60 to 80% oleic acid), medium in polyunsaturated fatty acid (4 to 20%), and small amounts of polyphenols, tocopherols, sterols, and many aromatic compounds (Montedoro and Garofolo, 1984; Mataix and Martinez, 1988; Tous and Romero, 1993). Fatty acid proportions vary in olive oil depending on region, cultivar and year (Fiorino, 1996; Uceda and Hermoso, 1997). Around 10% of the olive oil produced in the world is top quality virgin olive oil. The rest has to be refined to remove impurities which affect the flavour and aroma of the final oil (Ridgway, 1996).
Olive oil improves the taste of food, especially less fatty foods, making them much more appetising. A good fruity olive oil adds an exquisite flavour. Olive oils are excellent with all raw foods, particularly for seasoning salads, making mayonnaise and other sauces, when spread on toasted bread, for making vinaigrette, and as a dressing for hot or cold dishes such as cooked vegetables, soups, poached or broiled fish or meat, etc. Oil is well suited to preparing food at high temperatures, such as sautéed food, hearty soups, roasting, broiling, or frying, because of its stability. This is due to its predominantly monounsaturated fatty acid structure and to the antioxidant, protective effect of the tocopherols and polyphenols it contains. Animal fats oxidize quickly because of the lack of antioxidant substances; the same is true for seed oils, owing to their more unsaturated components. Olive oil's biological and therapeutic value is related in many aspects to its chemical structure mentioned above, particularly in the digestive system, in the critical stages of life (infancy and old age) and the circulatory system. For further information on olive oil composition, its medical and biological uses and the characteristics of virgin olive oils, see Christakis et al. (1982), Tiscornia et al. (1982), Fiorino (1996) and Viola (1997).
The Mediterranean diet is a modern nutritional concept said to promote a long and vigorous life. Originally based on the foods eaten by the people of Greece, southern Italy and Spain, this was first proposed by the American scientist Ancel Keys in 1955. The idea was based on the premise that animal fats were bad for heart disease but that unsaturated plant fats or oils promoted good health. To make olives edible fermentation, salt treatment or drying to remove the bitterness due to polyphenolic compounds and in particular 'oleuropein' modify the fruit flesh. Olive fruits are rich in oil and therefore high in energy. They are a good source of protein and b-carotene and contain other useful nutrients such as sugars, vitamins B, C and E, iron and other minerals (calcium and potassium). For further information on olive oil composition, its medical and biological uses and the characteristics of virgin olive oils, see Christakis et al. (1982), Tiscornia et al. (1982), Fiorino (1996) and Viola (1997). Olive oil is obtained by pressing or centrifuging the crushed fruit including the seed. All olive oils obtained from olives are classified as Virgin Olive Oils with the highest quality being 'extra virgin olive oil'. This category is high in monounsaturated fatty acid (60 to 80% oleic acid), medium in polyunsaturated fatty acid (4 to 20%) and small amounts of polyphenols, tocopherols, sterols and many aromatic compounds (Montedoro and Garofolo, 1984; Mataix and Martinez, 1988; Tous and Romero, 1993).
O. europaea subsp. europaea also has a great number of subsidiary uses. Mature trees are used for animal feed (leaves and olives that have fallen to the ground). Crop processing residues such as pomace are used for fuel and compost. Olive tree is widely planted as an ornamental and shade tree on the streets of several countries. The timber is durable and is used for furniture, kitchen utensils and decorative items. It also has been recommended for planting as a windbreak around orchards.
Olives have a very long and distinguished symbolic history. The olive branch was (and still is) a symbol of abundance, glory and peace. The leafy branches of the olive tree were ritually offered to deities and powerful figures as emblems of benediction and purification and they were used to crown the victors of friendly games and bloody wars. Today, olive branches and olive oil are still used in many religious ceremonies. Olive trees played important roles in Greek and Roman stories and are mentioned in the Torah, the Bible and the Quran.
Similarities to Other Species/ConditionsTop of page
The closest relative is of course O. europaea subsp. cuspidata, from which O. europaea subsp. europaea was probably derived many centuries ago (Mabberley, 2002). O. europaea subsp. cuspidata differs in its smaller fruit and its leaves, which have pale greenish-brown undersides and prominently hooked tips (Queensland Government, 2016).
Queensland Government (2016) lists a number of Australian native species that can be confused with O. europaea subsp. europaea. These include O. paniculata which has oppositely arranged leaves with paler green hairless undersides and its fleshy fruit are only about 10 mm long. The northern olive (Chionanthus ramiflora) also has oppositely arranged leaves with paler green hairless undersides and its fleshy fruit are relatively small (10-25 mm long). The mock olives (Notelaea spp.) also have oppositely arranged leaves and the undersides can be either hairy or hairless. The flowers are borne in unbranched clusters and again their fleshy fruits are relatively small at 5-20 mm long.
Prevention and ControlTop of page
Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.
Good husbandry making sure crops are kept clean and tidy would help prevent the spread of O. europaea subsp. europaea, as would the use of netting to protect the crop from bird predation. Other methods such as appropriate orchard design and operations (for example using decoy crops of non-commercially harvestable fruit or berry trees or shrubs which ripen as the same time as olives) should take place and abandoned olive groves should be destroyed (Spennemann and Allen, 2000a).
In South Australia O. europaea subsp. europaea is regarded as a significant environmental weed and it is recorded as an environmental weed across all Australian territories. It has been listed as a priority environmental weed in at least one Natural Resource Management region (Queensland Government, 2016). In Tasmania a number of measures such as an olive register, a code of practice, risk assessment and education of both commercial growers and home gardeners have been put in place to prevent further spread (ISSG, 2016)
Cultural Control and Sanitary Measures
Low intensity fire is likely to kill seedlings up to 1 m high (von Richter et al., 2005) however, this method is ineffective towards older plants which can regenerate readily from a lignotuber structure at the base of the trunk (Cuneo and Leishman, 2006),
Young seedlings (10 cm or less) can be hand-pulled and this is best done when the soil is moist (Cuneo and Leishman, 2006). However, cutting down existing bushes and grubbing the stump and roots usually results in heavy regeneration of seedlings (Parsons and Cuthbertson, 1992).
Mature plants are best controlled by cut-stump or basal bark treatments, using undiluted picloram + triclopyr, triclopyr or 2,4-D ester applied over the whole stump for the cut-stump treatment, or triclopyr + diesel oil applied to the bottom 50-60ncm of the tree trunk (Parsons and Cuthbertson, 1992). Young seedlings can be treated with 2,4-D amine or glyphosate (the latter should not be used in a grassy sward) and seedlings between six months and two years old can be treated with triclopyr or triclopyr + picloram (Parsons and Cuthbertson, 1992). Plants can also be treated using a cut stump treatment with undiluted glyphosate or by foliar and basal bark sprays (Cuneo and Leishman, 2006). Whist chemical control is readily achieved, the plants removed must be replaced as soon as possible with useful species, often utilizing a vigorous well-maintained pasture (Parsons and Cuthbertson, 1992).
Control by Utilization
Parsons and Cuthbertson (1992) recommend increased grazing pressure as a way of readily getting control of infestations.
ReferencesTop of page
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ContributorsTop of page
25/05/2016 Original text by:
Ian Popay, Landcare Research, New Zealand
Distribution MapsTop of page
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