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Hippophae rhamnoides L., Sea-buckthorn

Account Summary

Introduction, neophyte, deliberately planted, very rare. European boreo-temperate, but widely naturalised beyond its native occurrence.

1948; MCM & D; Crom Castle Estate.

Fermanagh occurrence

This extremely thorny, much-branched, thicket-forming, root-nodule bearing, dioecious shrub, 1-11 m in height was deliberately planted on the shore of Upper Lough Erne in the Crom Castle estate, which is the solitary station for the plant in Fermanagh to date. It was recorded as still present by the staff of the National Trust sometime between 1980 and 1990.

Vegetative reproduction

H. rhamnoides, which is deciduous, has very vigorous growth and strong powers of vegetative spread by means of both a suckering rhizome and by layering, especially when growing in suitably open soils (preferably sand or gravel) and in the well-lit, wind-sheltered habitats the shrub requires (H. Ainsworth, in: Stewart et al. 1994).

Flowering reproduction

Sea-buckthorn bushes flower in the winter and early spring before the leaves appear, a feature that assists its wind-pollination. Both male and female shrubs bear their flowers on the previous year's growth (Tutin et al. 1968). The male flowers are borne in small spikes or catkins of 4-8 reduced flowers, each consisting of four stamens and two sepals borne on a short receptacle (Pearson & Rogers 1962). The female bushes produce their flowers just as the first leaves open and are borne in short axillary racemes. The solitary, sessile ovary at the base of the perigynous receptacle contains a single ovule. The fruit is a solitary seeded achene, enclosed in the orange swollen fleshy receptacle and they appear as dense clusters of 6-10 mm diameter orange berries in the autumn (Pearson & Rogers 1962). They are attractive to birds, especially those of the Thrush family and the Magpie, whenever other food is limited (Lang 1987; Snow & Snow 1988).

The size of the introduced colony of Sea-buckthorn at the Crom estate has not been ascertained by us, but the plant has the ability to spread, naturalise and become an invasive nuisance in other plant communities, as it has done in several coastal dune systems around NI (FNEI 3). On account of this its distribution should be kept under review.

An important, briefly dominant, shrubby colonist of open areas in the Late-glacial period prior to its replacement by taller, shading trees (Godwin 1975), H. rhamnoides is considered native in B & I only on some stretches of the E coast of England from Bamburgh in Northumberland (VC 67) to Hastings in E Sussex (VC 14). As the New Atlas map indicates, it is introduced in very many coastal and a much smaller number of inland sites in Britain, and to a lesser extent in Ireland, although here it is almost exclusively coastal. The most inland Irish station mapped is at Crom in Fermanagh.

Typical habitats in B & I include stabilised sand-dunes, coastal banks and sea cliffs, although in coastal situations it always grows best when sheltered from the wind. The soil reaction where it grows is always neutral or basic and the root nodules probably fix nitrogen. The fact that nettles (Urtica spp.) are very frequently associated with Sea-buckthorn stands, they being strongly nitrophilous, does suggest that N-fixation is taking place (Pearson & Rogers 1962).

European and world occurrence

Hultén & Fries (1986) describe this is a Eurasiatic species that includes as many as nine subspecies. Apart from coastal habitats, as in B & I, H. rhamnoides occurs on the continent on river gravel, alluvium and lateral moraines in mountain regions in Europe and Asia. It is considered native throughout a considerable portion of Europe from 68°N in Norway to N Spain, C Italy and Bulgaria, and from NW France to Finland and Moldavia. It is, however, local in its occurrence and absent from wide areas of the continent. At the same time, it is frequently planted for ornament in gardens and parks, or to stabilise sand or gravel and it has become naturalised in many places (Tutin et al. 1968).

The overall distribution as mapped by Hultén & Fries (1986, Map 1310) shows H. rhamnoides s.l. stretching from the Pyrenees eastwards through C Europe, the Caucasus and the C Asiatic mountains to the highlands of N China.

Threats

The colonizing ability of this introduced spiny shrub and the difficulty and expense of eradicating or controlling it mean it should be regularly monitored, which is probably not happening at present.