Elaeagnus

Elaeagnus is a genus of about 50–70 species of flowering plants in the family Elaeagnaceae. Species of the genus are commonly known as silverberry or oleaster,

Description
Elaeagnus plants are deciduous or evergreen shrubs or small trees. The alternate leaves and the shoots are usually covered with tiny silvery to brownish scales, giving the plants a whitish to grey-brown colour from a distance. The flowers are small, with a four-lobed calyx and no petals; they are often fragrant. The fruit is a fleshy drupe containing a single seed; it is edible in many species. Several species are cultivated for their fruit, including E. angustifolia, E. umbellata, and E. multiflora (gumi). E. umbellata contains the carotenoid lycopene.

Taxonomy
The genus Elaeagnus was erected in 1754 by Carl Linnaeus, who attributed the name to Joseph Pitton de Tournefort. There is agreement that the name is based on Theophrastus's use of the Ancient Greek ἐλαίαγνος (, latinized to ) as the name of a shrub. The first part of the name, elae-, is from ἐλαία, 'olive'. Sources differ on the origin of the second part: it may be from ἄγνος, Vitex agnus-castus, the chaste tree, or from the Greek name for a kind of willow. In either case, the second part is derived from ἁγνός, meaning 'pure', 'chaste'.

Species
Elaeagnus comprises the following species:


 * 1) Elaeagnus angustata (Rehder) C.Y.Chang (China)
 * 2) Elaeagnus angustifolia L. – oleaster, Russian silverberry, or Russian olive (western Asia)
 * 3) Elaeagnus annamensis S.Moore
 * 4) Elaeagnus argyi H.Lév. (China)
 * 5) Elaeagnus bambusetorum Hand.-Mazz. (China)
 * 6) Elaeagnus bockii Diels (China)
 * 7) Elaeagnus bonii Lecomte
 * 8) Elaeagnus calcarea Z.R.Xu
 * 9) Elaeagnus caudata Schltdl. ex Momiy.
 * 10) Elaeagnus cinnamomifolia W.K.Hu & H.F.Chow (China)
 * 11) Elaeagnus commutata Bernh. ex Rydb. – American silverberry or wolf-willow (North America)
 * 12) Elaeagnus conferta Roxb. (southern Asia)
 * 13) Elaeagnus courtoisii Belval (China)
 * 14) Elaeagnus davidii Franch. (China)
 * 15) Elaeagnus delavayi Lecomte (China)
 * 16) Elaeagnus difficilis Servett. (China)
 * 17) Elaeagnus epitricha Momiy. ex H.Ohba
 * 18) Elaeagnus fasciculata Griff.
 * 19) Elaeagnus formosana Nakai (Taiwan)
 * 20) Elaeagnus formosensis Hatus.
 * 21) Elaeagnus geniculata D.Fang
 * 22) Elaeagnus glabra Thunb. (eastern Asia)
 * 23) Elaeagnus gonyanthes Benth. (China)
 * 24) Elaeagnus griffithii Servett. (China)
 * 25) Elaeagnus grijsii Hance (China)
 * 26) Elaeagnus guizhouensis C.Y.Chang (China)
 * 27) Elaeagnus henryi Warb. ex Diels (China)
 * 28) Elaeagnus heterophylla D.Fang & D.R.Liang
 * 29) Elaeagnus hunanensis C.J.Qi & Q.Z.Lin
 * 30) Elaeagnus indica Servett.
 * 31) Elaeagnus infundibularis Momiy.
 * 32) Elaeagnus jiangxiensis C.Y.Chang (China)
 * 33) Elaeagnus jingdonensis C.Y.Chang (China)
 * 34) Elaeagnus kanaii Momiy. (China)
 * 35) Elaeagnus lanceolata Warb. (China)
 * 36) Elaeagnus lanpingensis C.Y.Chang (China)
 * 37) Elaeagnus laosensis Lecomte
 * 38) Elaeagnus latifolia L. (southern Asia)
 * 39) Elaeagnus lipoensis Z.R.Xu
 * 40) Elaeagnus liuzhouensis C.Y.Chang (China)
 * 41) Elaeagnus longiloba C.Y.Chang (China)
 * 42) Elaeagnus loureiroi Champ. (southern China)
 * 43) Elaeagnus luoxiangensis C.Y.Chang (China)
 * 44) Elaeagnus luxiensis C.Y.Chang (China)
 * 45) Elaeagnus macrantha Rehder (China)
 * 46) Elaeagnus macrophylla Thunb. (eastern Asia)
 * 47) Elaeagnus magna (Servett.) Rehder (China)
 * 48) Elaeagnus matsunoana Makino
 * 49) Elaeagnus maximowiczii Servett.
 * 50) Elaeagnus micrantha C.Y.Chang (China)
 * 51) Elaeagnus mollis Diels (China)
 * 52) Elaeagnus montana Makino
 * 53) Elaeagnus morrisonensis Hayata (Taiwan)
 * 54) Elaeagnus multiflora Thunb. – cherry silverberry or gumi (eastern Asia)
 * 55) Elaeagnus murakamiana Makino
 * 56) Elaeagnus nanchuanensis C.Y.Chang (China)
 * 57) Elaeagnus obovata H.L.Li (China)
 * 58) Elaeagnus obovatifolia D.Fang
 * 59) Elaeagnus obtusa C.Y.Chang (China)
 * 60) Elaeagnus oldhamii Maxim. (China)
 * 61) Elaeagnus ovata Servett. (China)
 * 62) Elaeagnus pallidiflora C.Y.Chang (China)
 * 63) Elaeagnus parvifolia Wall. ex Royle (central Asia)
 * 64) Elaeagnus pilostyla C.Y.Chang (China)
 * 65) Elaeagnus pingnanensis C.Y.Chang (China)
 * 66) Elaeagnus pungens Thunb. – silverthorn (Japan)
 * 67) Elaeagnus pyriformis Hook.f. (eastern Himalaya)
 * 68) Elaeagnus retrostyla C.Y.Chang (China)
 * 69) Elaeagnus rhamnoides (L.) A.Nelson
 * 70) Elaeagnus rivularis Merr.
 * 71) Elaeagnus rotundata Nakai
 * 72) Elaeagnus sarmentosa Rehder (China)
 * 73) Elaeagnus schlechtendalii Servett. (China)
 * 74) Elaeagnus songarica Schltr.
 * 75) Elaeagnus s-stylata Z.R.Xu
 * 76) Elaeagnus stellipila Rehder (China)
 * 77) Elaeagnus takeshitai Makino
 * 78) Elaeagnus taliensis C.Y.Chang (China)
 * 79) Elaeagnus tarokoensis S.Y.Lu & Yuen P.Yang
 * 80) Elaeagnus thunbergii Servett. (China)
 * 81) Elaeagnus tonkinensis Servett. (southeastern Asia)
 * 82) Elaeagnus tricholepis Momiy.
 * 83) Elaeagnus triflora Roxb. (southeastern Asia, northeast Australia)
 * 84) Elaeagnus tubiflora C.Y.Chang (China)
 * 85) Elaeagnus tutcheri Dunn (southern China)
 * 86) Elaeagnus umbellata Thunb. – Japanese silverberry or autumn olive (eastern Asia)
 * 87) Elaeagnus viridis Servett. (China)
 * 88) Elaeagnus wenshanensis C.Y.Chang (China)
 * 89) Elaeagnus wilsonii H.L.Li (China)
 * 90) Elaeagnus wushanensis C.Y.Chang (China)
 * 91) Elaeagnus xichouensis C.Y.Chang (China)
 * 92) Elaeagnus xingwenensis C.Y.Chang
 * 93) Elaeagnus xizangensis C.Y.Chang (China)
 * 94) Elaeagnus yoshinoi Makino
 * 95) Elaeagnus yunnanensis Servett.

Species names with uncertain taxonomic status
The status of the following species is unresolved:


 * Elaeagnus arakiana Koidz.
 * Elaeagnus asakawana Sa.Kurata
 * Elaeagnus attenuata Nakai
 * Elaeagnus crocea Nakai
 * Elaeagnus cyanea Aiton ex Steud.
 * Elaeagnus emarginata Colla
 * Elaeagnus fasciculata (Wall. ex Steud.) A.Nelson
 * Elaeagnus fragrans Nakai
 * Elaeagnus fruticosa (Lour.) A.Chev.
 * Elaeagnus fusca Pépin ex Lem.
 * Elaeagnus higoensis Nakai
 * Elaeagnus kiusiana Nakai
 * Elaeagnus laetevirens Lindb.
 * Elaeagnus latifolia Lour.
 * Elaeagnus mayeharai Nakai
 * Elaeagnus nagasakiana Nakai
 * Elaeagnus numajiriana Makino
 * Elaeagnus oleaster L.
 * Elaeagnus pauciflora C.Y. Chang (China)
 * Elaeagnus philippinensis Perrott. – lingaro berry (Philippines)
 * Elaeagnus × pyramidalis Browicz & Bugala (E. commutata × E. multiflora)
 * Elaeagnus oxycarpa Schltdl. (China)
 * Elaeagnus rotundifolia (Parry) A.Nelson
 * Elaeagnus sativa Dippel
 * Elaeagnus undulata auct.
 * Elaeagnus utilis A.Nelson
 * Elaeagnus veteris-castelli Lepage
 * Elaeagnus yakusimensis Masam.

Hybrids
The following hybrids have been described:
 * Elaeagnus × maritima Koidz.
 * Elaeagnus × reflexa E.Morren & Decne. (E. pungens × E. glabra)
 * Elaeagnus × submacrophylla Servett. (E. macrophylla × E. pungens)

Habitat
The vast majority of the species are native to temperate and subtropical regions of Asia. Elaeagnus triflora extends from Asia south into northeastern Australia, while E. commutata is native to North America, and Elaeagnus philippinensis is native to the Philippines. One of the Asian species, E. angustifolia, may also be native in southeasternmost Europe, though it may instead be an early human introduction there. Also, several Asiatic species of Elaeagnus have become established as introduced species in North America, with some of these species being considered invasive, or even designated as noxious, in portions of the United States.

Ecology
Elaeagnus species are used as food plants by the larvae of some Lepidoptera species including Coleophora elaeagnisella and the Gothic moths. The thorny shrubs can also provide good nesting sites for birds.

Nitrogen fixation
Many Elaeagnus species harbor nitrogen-fixing organisms in their roots, so are able to grow well in low-nitrogen soils. This ability results in multiple ecological consequences where these Elaeagnus species are present. They can become invasive in many locations where they are established as exotic species. Two species (E. pungens and E. umbellata) are currently rated as category II noxious, invasive species in many world regions and by the Florida Exotic Pest Plant Council.

Cultivation
Elaeagnus species are widely cultivated for their showy, often variegated, foliage, and numerous cultivars and hybrids have been developed.

The fruit is acidic and somewhat astringent. It makes good tarts.

Notable species and hybrids in cultivation include:-
 * Elaeagnus angustifolia
 * Elaeagnus commutata
 * Elaeagnus macrophylla
 * Elaeagnus multiflora
 * Elaeagnus pungens
 * Elaeagnus × reflexa
 * Elaeagnus × submacrophylla (syn. E. × ebbingei)
 * Elaeagnus umbellata

The hybrid Elaeagnus × submacrophylla and the cultivar 'Gilt Edge' have gained the Royal Horticultural Society's Award of Garden Merit.