Elaeagnus is a genus of ca. 40 species, almost exclusively distributed in temperate E-Asia and with an additional species in North America (E. commutata Bernh.). None is native in Belgium. About eight species are cultivated as ornamentals in Europe (Barnes & Whiteley 1997). Some species of Elaeagnus are reputed environmental weeds.
The identification of Elaeagnus in Belgium is difficult and several species have long been confused. As a rule, collections or fieldnotes of Elaeagnus are preferably made at different stages (at anthesis, at fruiting and during winter).
The North American Elaeagnus commutata (and/or its putative hybrid with E. angustifolia, E. ‘Quicksilver’) should be looked for. Its shoots are unarmed and leaves are equally silvery whitish on upper and lower surface. It is probably cultivated in Belgium too and has been (correctly?) reported as an escape in various European countries (see for instance Clement & Foster 1994, van der Meijden 2005).
1. Evergreen shrub. Leaves coriaceous. Flowering in autumn === 2
1. Deciduous shrub or small tree. Leaves herbaceous or chartaceous. Flowering in spring or early summer === 3
2. Shoots spineless === Elaeagnus x submacrophylla
2. Shoots with scattered stout thorns === E. pungens
3. Upper side of young leaves with indumentum of dense silvery scales or stellate hairs (sometimes glabrescent with age). Ripe berries yellowish, mealy. Shoots usually spiny. Style surrounded at base by conspicuous conical disc === E. angustifolia
3. Upper side of leaves soon becoming glabrous, green. Ripe berries red, juicy. Shoots usually spineless. Style without conspicuous disc at base === 4
4. Flowers 1-7 in leaf-axils, pedicels 3-7(-12) mm long. Berry 6-8 mm long. Perigynous zone tapered at base. Upper surface of young leaves with minute scale-like hairs (soon glabrescent), diameter of the disc of the hair wider than the length of the branches === E. umbellata
4. Flowers 1-3 in leaf-axils, pedicels 15-50 mm long. Berry ca. 15 mm long. Perigynous zone abruptly constricted above ovary. Upper surface of young leaves with minute stellate hairs (soon glabrescent), branches much longer than the disc of the hair === E. multiflora var. hortensis
Barnes P.G. & Whiteley A.C. (1997) Elaeagnus. In Cullen et al. (eds.) The European Garden Flora. Vol. 5. Cambridge University Press : 245-247.
Clement E.J. & Foster M.C. (1994) Alien plants of the British Isles. BSBI, London: XVIII + 590 p.
Ohba H. (1999) Elaeagnaceae. In: Iwatsuki K. & al. (eds.), Flora of Japan, vol. IIc. Kodansha, Tokyo: 152-158.
Roloff A. & Bärtels A. (2006) Flora der Gehölze (2e Auflage). Ulmer, Stuttgart: 844 p.
Servettaz C. (1909) Monographie des Eléagnacées. Beihefte Bot. Centralbl. 25: 1-128.
Sun M. & Lin Q. (2010) A revision of Elaeagnus L. (Elaeagnaceae) in mainland China. Journal of Systematics and Evolution 48(5): 356-390. [available online at: https://www.researchgate.net/publication/261537119_A_revision_of_Elaeagnus_L._%28Elaeagnaceae%29_in_mainland_China]
Van der Meijden R. (2005) Heukels’ Flora van Nederland (23e druk). Wolters-Noordhoff, Groningen: 685 p.