Olive (Olea europaea)

Description

What’s the World’s Favourite Species?

Olive fact file

• Description
• Biology
• Range
• Habitat
• Status
• Threats
• Conservation
• Find out more
• Glossary
• References
• Print factsheet

Olive description

One of the world’s oldest cultivated plants ^{(3) (4)}, the olive (Olea europaea) has shaped both the culture and the landscape of the Mediterranean for thousands of years. Economically valuable for the oil extracted from its fruits, the olive has long been a symbol of wealth, long life, abundance, power and peace, and has been enshrined in legends as well as in the symbology of major religions ^{(2) (4) (5)}.

The olive grows as an evergreen shrub or tree ^{(2) (3) (5) (6)}, with thick, leathery leaves that grow in opposite pairs along the stems ^{(2) (3) (4) (6)}. The leaves are oblong to lance-shaped ^{(3) (4) (7)} and measure around 3 to 9 centimetres in length and 0.3 to 3 centimetres in width ^{(2) (3)}. The upper surface of the leaf is usually grey-green, while the lower surface is silvery to yellowish-green ^{(2) (4) (5) (7)}. Each leaf typically grows over a period of two years before being shed ⁽⁶⁾.

The flowers of the olive grow in clusters at the base of the leaves, where the leaf meets the stem of the plant ^{(2) (3) (4) (6)}. Each cluster, or inflorescence, typically contains between 15 and 30 tiny, fragrant, white to yellowish-white flowers ^{(4) (5) (6) (7)}. The petals of the olive flower are fused, forming a short tube with four lobes ^{(2) (3) (6) (7)}.

The well-known fruit of the olive is a fleshy drupe containing a hard stone that encloses the seed ^{(2) (3) (4) (6) (8)}. The olive fruit is purple-black when ripe ^{(3) (7)} and measures between 0.5 and 4 centimetres in length ⁽³⁾.

Around six subspecies of the olive are usually recognised: Olea europaea subsp.europaea, Olea europaea subsp. cuspidata, Olea europaea subsp. laperrinei, Olea europaea subsp. maroccana, Olea europaea subsp. cerasiformis and Olea europaea subsp. guanchica ^{(2) (3)}. These differ mainly in the size and shape of their leaves and in the size of their fruits, and some have been considered to be distinct species ⁽³⁾. Other scientists recognise just two subspecies, the European olive (Olea europaea subsp.europaea) and the African olive (Olea europaea subsp. cuspidata) ⁽¹⁾.

The subspecies Olea europaea subsp.europaea is divided into two ‘varieties’. The variety europaea, the cultivated olive, is not known from the wild and has much larger, fleshier fruits than its wild relative, the variety sylvestris ^{(2) (3)}. As well as smaller fruits, the wild variety has characteristically dense, shrubby growth. The ancestry and origins of the cultivated form are unclear ^{(3) (6)}.

Also known as

African olive, European olive, olive tree.

Synonyms

Olea africana, Olea asiatica, Olea aucheri, Olea chrysophylla, Olea chrysophylla var. maderensis, Olea cuspidata, Olea europaea africana, Olea europaea subsp. africana, Olea europaea subsp. maderensis, Olea europaea var. buxifolia, Olea europaea var. cerasiformis, Olea europaea var. maderensis, Olea ferruginea, Olea indica, Olea kilimandscharica, Olea laperrinei, Olea maroccana, Olea monticola, Olea oleaster, Olea salicifolia, Olea sativa, Olea sativa var. verrucosa, Olea schimperi, Olea similis, Olea somaliensis, Olea subtrinervata, Olea verrucosa.

Size

Height: up to 15 m ^{(2) (3)}

Olive biology

The flowers of the olive usually form in spring ^{(4) (6) (7)}, and are pollinated by insects ^{(7) (8)}. Two types of flowers may be present: hermaphroditic flowers, containing both male and female reproductive parts, and unisexual flowers, containing only male reproductive parts ^{(3) (6)}.

The fruits of cultivated olives usually ripen in the autumn ^{(2) (6)}, and the seeds of this species are likely to be dispersed by birds ^{(8) (9)}. Although the fruits of the cultivated olive are widely eaten, those of its wild relatives are generally bitter and inedible ^{(4) (7)}.

The olive matures quite slowly but can be remarkably long-lived, with reports of individual trees living for over 1,000 years ^{(2) (5) (6)}.

All parts of the olive tree have been widely used by humans, and this species is said to be the Mediterranean region’s most valuable and versatile crop ⁽²⁾. The main product of the tree is olive oil, which is extracted from its fruits and used in a wide range of applications from food to medicine and fuel ^{(2) (4)}. The fruits themselves are also used for food, while various parts of the plant have been used in traditional medicine, and the wood has been used for fuel, construction and furniture ^{(2) (4) (7)}. The foliage of the olive can be used as animal feed ⁽⁴⁾.

The olive is also planted as an ornamental tree, as well as to control soil erosion and to form firebreaks ⁽²⁾.

Olive range

The olive has a wide distribution across the Mediterranean region, Africa and Asia ^{(2) (3) (9)}. The subspecies O. e. europaea occurs in the Mediterranean, while O. e. cuspidata is found from southern China, through Asia and Arabia to eastern and southern Africa. O. e. laperrinei occurs in three isolated populations in the Sahara and O. e. maroccana is found in an isolated population in the High Atlas Mountains of Morocco. O. e. cerasiformis is restricted to the island of Madeira and O. e. guanchica is restricted to the Canary Islands ^{(2) (3)}.

In addition to this widespread distribution, the olive has been introduced to many countries outside its natural range, including Australia, New Zealand, Ecuador, French Polynesia, the United States and Hawaii ^{(3) (9)}.

Olive habitat

The olive typically grows in seasonally dry Mediterranean-type habitats, as well as in bushland in the tropics ⁽²⁾.

Olive status

The olive has yet to be classified by the IUCN.

Olive threats

The olive is a widespread species and is not currently known to be threatened. In some areas, such as Australia and Hawaii, it has become an invasive weed, escaping from cultivation and forming dense stands which can shade out native vegetation and increase the fire hazard in dry habitats ^{(8) (9)}.

Although the species as a whole is not at risk of extinction, some subspecies of the olive may potentially be under threat due to their very limited distributions ⁽⁹⁾.

Olive conservation

There are not known to be any specific conservation measures currently in place for the olive. However, tests have been carried out on the storage and germination of olive seeds as part of the Millennium Seed Bank Partnership at the Royal Botanic Gardens, Kew ⁽²⁾.

In areas where the olive is invasive, management measures are sometimes in place to control it and to protect native vegetation ⁽⁹⁾.

Find out more

Find out more about the olive:

• Royal Botanic Gardens, Kew - Olea europaea:
  http://www.kew.org/plants-fungi/Olea-europaea.htm

More information on conservation in the Mediterranean region:

• Conservation International: Biodiversity Hotspots - Mediterranean Basin:
  http://www.biodiversityhotspots.org/xp/hotspots/mediterranean/Pages/default.aspx
• ARKive - Mediterranean Basin:
  http://www.arkive.org/eco-regions/mediterranean-basin/

Authentication

This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:
arkive@wildscreen.org.uk

Glossary

Drupe

Fleshy fruit with single seed enclosed in a woody covering. Cherries, peaches and plums are all drupes.

Evergreen

A plant which retains leaves all year round. This is in contrast to deciduous plants, which completely lose their leaves for part of the year.

Hermaphroditic

Possessing both male and female sex organs.

Inflorescence

The reproductive shoot of a plant, which bears a group or cluster of flowers.

Pollinate

To transfer pollen grains from the stamen (male part of a flower) to the stigma (female part of a flower) of a flowering plant. This usually leads to fertilisation, the development of seeds and, eventually, a new plant.

Subspecies

A population usually restricted to a geographical area that differs from other populations of the same species, but not to the extent of being classified as a separate species.

Variety

In taxonomy, the science of classifying organisms, variety is the rank below subspecies. Members of a variety differ from others of the same species in relatively minor ways.

References

1. Integrated Taxonomic Information System (ITIS) (December, 2011)
   http://www.itis.gov/
2. Royal Botanic Gardens, Kew - Olea europaea (December, 2011)
   http://www.kew.org/plants-fungi/Olea-europaea.htm
3. Green, P.S. (2002) A revision of Olea L. (Oleaceae). Kew Bulletin, 57(1): 91-140.
4. Bartolini, G. and Petruccelli, R. (2002) Classification, Origin, Diffusion and History of the Olive. Food and Agriculture Organization of the United Nations, Rome.
5. Therios, I. (2009) Olives. Crop Production Science in Horticulture 18. CABI, Wallingford, UK.
6. Martin, G.C. (2003) Olea europaea L. In: Woody-Plant Seed Manual. USDA Forest Service, Dry Branch, Georgia. Available at:
   http://nsl.fs.fed.us/wpsm/Olea.pdf
7. Jongbloed, M. (2003) The Comprehensive Guide to the Wildflowers of the United Arab Emirates. Environmental Research and Wildlife Development Agency, Abu Dhabi.
8. Kubitzki, K. and Kadereit, J.W. (Eds.) (2004) The Families and Genera of Vascular Plants. Volume VII: Flowering Plants. Dicotyledons: Lamiales (except Acanthaceae including Avicenniaceae). Springer-Verlag, Berlin and Heidelberg.
9. Global Invasive Species Database - Olea europaea (December, 2011)
   http://issg.org/database/species/ecology.asp?si=1585&fr=1&sts=&lang=EN