• Family: Oleaceae
• Genus: Olea
• Species: europaea
• Varieties
• Sweet Olive
• Russian Olive
   

Classification varies with different schemes.  After a century of languishing, taxonomy is currently a hot scientific field with the advent of gene sequencing. According to classical taxonomy:

According to the tree of life:

Known as the Olive Family, it comprises 600 species in 24 genera (one extinct) and occur on all continents. Other Genera in the family Olieaceae are: Ligustrum (Privet), Syringa (lilac), Fraxinus (ash) and Olea (olive).  From Johnson 1957:

Habit and leaf form. Trees and shrubs, or lianas (sometimes). Self supporting, or climbing; the climbers tem twiners, or scrambling; Jasminum twining anticlockwise. Leptocaul. Mesophytic. Leaves deciduous often), or evergreen; opposite (nearly always), or alternate; in Jasminum, spiral; petiolate; non-sheathing; imple, or compound; when compound ternate, or pinnate. Lamina when simple dissected, or entire; innately veined; cross-venulate. Leaves exstipulate. Lamina margins entire, or serrate, or dentate. egetative buds scaly. Leaves without a persistent basal meristem. Domatia recorded (6 genera and numerous pecies); represented by pits, or pockets, or hair tufts.

Leaf anatomy. Stomata usually anomocytic. Hairs present. Complex hairs present; usually peltate.

The mesophyll with sclerencymatous idioblasts (often), or without sclerenchymatous idioblasts. Minor leaf veins without phloem transfer cells (7 genera).

Stem anatomy. Cork cambium present; initially deep-seated (rarely), or superficial. Nodes unilacunar. Internal phloem absent. Secondary thickening developing from a conventional cambial ring. ‘Included’ hloem absent. Xylem with tracheids, or ithout tracheids; with fibre tracheids, or without fibre tracheids. Vessel end-walls scalariform, or scalariform and simple (with few cross bars). Vessels with vestured pits, or without vestured pits. Wood parenchyma paratracheal (typically), or potracheal (occasionally diffuse, or absent).

Reproductive type, pollination. Plants hermaphrodite (usually), or polygamomonoecious.

Inflorescence, floral, fruit and seed morphology. Flowers solitary, or aggregated in ‘inflorescences’. The terminal inflorescence unit cymose. Inflorescences racemes, panicles or fascicles. Flowers bracteate, or ebracteate; often fragrant; regular; usually 2–6 merous; tricyclic, or tetracyclic. Free hypanthium absent. Hypogynous disk present (around G), or absent; intrastaminal.

Perianth with distinct calyx and corolla (usually), or sepaline (the corolla sometimes lacking); typically 8; 2 horled (usually), or 1 whorled; isomerous. Calyx 4(–15); 1 whorled; gamosepalous; entire, or lobulate, or lunt-lobed, or toothed (sometimes obsolete); regular; valvate. Corolla when present (i.e. usually) 4(–12); 1 whorled; polypetalous (rarely, more or less), or gamopetalous; imbricate, or valvate (or induplicate-valvate), or contorted; regular.

Androecium 2 (usually), or 4 (rarely). Androecial members adnate (to the corolla), or free of the perianth; ree of one another; 1 whorled. Androecium exclusively of fertile stamens. Stamens 2(–4); reduced in number relative to the adjacent perianth; oppositisepalous; filantherous, or with sessile anthers. Anthers dorsifixed, or basifixed; dehiscing via longitudinal slits; introrse. Endothecium developing fibrous hickenings. Microsporogenesis simultaneous. The initial microspore tetrads tetrahedral, or isobilateral, or T-shaped, or linear. Anther wall initially with one middle layer, or initially with more than one middle layer. Tapetum glandular. Pollen grains aperturate; (2–)3(–4) aperturate; colpate, or colporate colporoidate, occasionally rupate); 2-celled, or 3-celled.

Gynoecium 2 carpelled. Carpels reduced in number relative to the perianth. The pistil 2 celled. Gynoecium syncarpous; synovarious to eu-syncarpous; superior. Ovary 2 locular. Gynoecium median, or transverse, or oblique; stylate. Styles 1; pical. Stigmas 2 lobed; dry type; papillate, or non-papillate; Group II type. Placentation axile. Ovules (1–)2(–50) per locule (usually two, but Jasminoideae with 1, 4 or ‘many’); pendulous, or ascending; with dorsal raphe; usually collateral; non-arillate; anatropous, or amphitropous; unitegmic; tenuinucellate. Endothelium differentiated. Embryo-sac development Polygonum-type, or Allium-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed; 3; not proliferating;

ephemeral. Synergids hooked. Endosperm formation cellular. Embryogeny caryophyllad, or solanad (?).

Fruit fleshy, or non-fleshy; dehiscent, or indehiscent, or a schizocarp. Mericarps when schizocarpic, 2; samaroid. Fruit when non-schizocarpic, a capsule, or a berry, or a drupe. Capsules loculicidal. Fruit 1–4 eeded. Seeds endospermic, or non-endospermic. Endosperm oily. Embryo rudimentary at the time of seed release (in Fraxinus excelsior), or weakly differentiated to well differentiated (?). Cotyledons 2. Embryo achlorophyllous (5/12); straight.

Seedling. Germination phanerocotylar, or cryptocotylar.

Physiology, biochemistry. Not cyanogenic. Alkaloids present (commonly), or absent. Iridoids detected; Route I’ type (normal and seco). Verbascosides detected (4 genera). Cornoside detected (Forsythia). Proanthocyanidins absent. Flavonols resent, or absent; quercetin, or kaempferol and quercetin. Ellagic acid absent (8 genera, species). Arbutin absent. Ursolic acid present. Saponins/sapogenins present, or absent. Aluminium accumulation not found. Sugars transported as oligosaccharides + sucrose, or as sugar alcohols + oligosaccharides + sucrose (and sucrose nowhere predominating, in the 6 genera sampled). C3. C3 physiology recorded directly in Ligustrum, Syringa.

Peculiar feature. The funicles not as in Acanthaceae.

Geography, cytology. Temperate to tropical. Cosmopolitan, save in frigid regions. X = 10, 11, 13, 14, 23, 24.

Taxonomy. Subclass Dicotyledonae; Tenuinucelli. Dahlgren’s Superorder Gentianiflorae; Oleales. Cronquist’s Subclass Asteridae; Solanales. APG (1998) Eudicot; core Eudicot; Asterid; Euasterid I; Lamiales. Species 900. Genera about 25; Abeliophyllum, Chionanthus, Comoranthus, Fontanesia, Forestiera, Forsythia, Fraxinus, Haenianthus, Hesperelaea, Jasminum, Ligustrum, Linociera, Menodora, Myxopyrum, Nestegis, Noronhia, Noronhia, Notelaea, Nyctanthes, Olea, Osmanthus, Phyllyrea, Picconia, Schrebera, Syringa Tessarandra.

Johnson 1957.

Economic uses, etc. Edible fruit and edible and medicinal ‘olive oil’ from Olea europaea, cultivated trees and shrubs, timber trees (Jasminum, Osmanthus, Forsythia, Syringa, Ligustrum, Fraxinus, etc.

L. Watson and M. J. Dallwitz (1992 onwards). The Families of Flowering Plants: Descriptions,

Illustrations, Identification, and Information Retrieval. Version: 14th December 2000. ttp://biodiversity.uno.edu/delta/’. Dallwitz (1980), Dallwitz, Paine and Zurcher (1993, 1995, 2000), and Watson and Dallwitz (1991)

There is only one species in this genus; europaea, which produces the edible olives and oil commonly consumed. There are about 40 other species in S. Africa, S. Asia, E. Australia and New Caledonia:

Olea brachiata
Olea capensis
Olea caudatilimba
Olea europaea
Olea exasperata
Olea guangxiensis
Olea hainanensis
Olea laxiflora
Olea neriifolia
Olea paniculata
Olea parvilimba
Olea rosea
Olea salicifolia
Olea tetragonoclada
Olea tsoongii
Olea undulata

There are many varieties of this species. Some, such as Ascolano and Sevillano are large with small pits and low oil content which are used  for making table olives. Others such as Frantoio, Argequina and Lucca are small but have a high oil content and are used for making olive oil.  For a large list of common varieties go to: Varieties

The Russian Olive or Oleaster

The Russian Olive is not used to make olives or olive oil. Elaeagnus angustifolia  is only remotely related to the olive tree. They share the same class, Magnoliopsida (Dicotyledons) but different order, species etc. There is evidence of cross-reactivity between olive, ash, privet, and Russian olive tree pollen allergens. (Annals of Allergy 69(6): 493-496) so if you are allergic to olive pollen don't plant Russian olive. Russian olive is a native of southern Europe and western Asia. It was introduced into the United States in the early 1900's and has now escaped cultivation and is extensively naturalized in 17 western states. According to the US forest service, once established, Russian-olive is hard to control and nearly impossible to eradicate. Control efforts have included mowing, cutting, burning, spraying, girdling, and bulldozing, most with limited success. It does produce a small fruit which is nutritious to deer, cattle, birds and rodents but when Russian olive displaces natural species the resultant habitat is generally considered inferior.

The Sweet Olive Tree

The Sweet olive, (Osmanthus fragrans) also known as tea olive, fragrant olive, is in the same Family (Oleacea) as the olive oil olive.  Other Genera in the family are: Ligustrum (Privet), Syringa (lilac), Fraxinus (ash) Synonyms:Olea fragrans, Olea ovalis, Osmanthus longibracteatus, Osmanthus macrocarpus The sweet olive does not make a seed with appreciable oil and is not used for making oil. Olive oil that is late harvest and has a sweeter, more ripe flavor is sometimes referred to as "sweet olive oil" on restaurant menus, as opposed to an astringent, bitter Tuscan style oil. Bland refined olive oil is also referred to as "sweet olive oil" when it is sold in drug stores for softening earwax, etc.

References:

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