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Buxus sempervirens L., Box

Account Summary

Introduction, planted or naturalised, very rare. Sub-Mediterranean-Sub-Atlantic, but widely naturalised.

11 June 1988; RHN & RSF; County Bridge, south of Garrison.

April to August.

Growth form, native status in England and preferred habitats

Although still considered native in up to ten famous, long-known sites on chalk and limestone in S England, in the vast majority of its other very numerous, widely scattered sites across B & I, this distinctive, slow-growing, evergreen shrub or small tree with opposite, dark green, smooth, leathery leaves, 1.2-2.5 cm in length, is now recognised as being a naturalised introduction of garden origin (Wigginton 1999).

Biogeographically, B. sempervirens is regarded as a Sub-Mediterranean or Sub-Mediterranean-subAtlantic species, and apart from the fact that Box appears as an element in many place names in S England, the reasons for doubting its native status in England was based on three additional pieces of evidence: the quite definite lack of a fossil (pollen or macrofossil) from the early part of the current Flandrian interglacial in B & I (although it had been recorded from the two previous interglacials – the Hoxnian and the Ipswichian) (Godwin 1975); the supposed (casually assumed) absence of Box from adjacent areas of N France, except where it had obviously been planted for game cover; and because the hard, fine-grained wood has always been considered a very valuable commodity, and therefore B. sempervirens might be one of the plants introduced to Britain by the Romans on account of its usefulness (Tansley 1939).

Native status is very important and significant within the framework of biological conservation efforts, often attracting Government and private funding for preservation and enhancement of existing sites. Research by Pigott & Walters (1953) showed that B. sempervirens remains present and appears perfectly native in numerous sites in N France that in geography and habitat conditions closely mirror existing Box sites in S England, and therefore no discontinuity whatsoever exists between English stands and those on the near continent. It is noted that several French local Floras have treated B. sempervirens as native in places around Paris and E, W & S Normandy (Pigott & Walters 1953). On account of the value of the wood, planting of Box-groves over several centuries has certainly augmented native stands in both France and England, but the evidence of Anglo-Saxon place names involving the element 'box' from the 8th century onwards indicates impressive antiquity to the stands of the plant.

After glacial ice melted, 10,000 BP, plants migrated back into B & I. Pigott & Walters (1954) suggest that, even with forest cover increasing (at first Betula and Pinus, later Quercus and Ulmus) chalk and limestone scarp slopes in southern Britain remained free of trees for a longer period into the post-glacial, due to removal by solifluction of pre-glacial soils, than did the neighbouring clay and plateau areas. These sites would have favoured the colonization by Buxus therefore and enabled the plant to spread over southern Britain on the chalk and northwards on the oolite, reaching the Carboniferous Limestone of the Lake District by the climatic optimum, 3,000 years after entering Britain. With an increasing forest cover, the Buxus distribution would have become fragmented, and the deterioration of the climate in the Sub-Atlantic Period restricted the range of the species until, in Neolithic to Roman times, it was confined to southern England, where it still occurs today (Staples 1970).

Box might therefore be native in at least a small number of southern localities, such as Box Hill in Surrey (VC 17), on unstable limestone landslip at Noar Hill, Hampshire (VC 12) (Brewis et al. 1996), and along ancient trackways, for instance the Fleam and Devil's Dyke in the Chilterns and Cotswolds, and this proposition is widely accepted today. Part of the argument hinges on archaeological finds of probable Box charcoal in association with Neolithic camps on the South Downs 2,000 years before the Roman invasion, suggesting (since Stone Age farmers are not considered to have been planters or importers), that B. sempervirens grew wild in S England at that time (Marren 1992).

B. sempervirens usually grows as an understorey tree or dense shrub in woodland on limestone (usually with Beech or Yew), or as a major component in woodland canopy, on chalk in S England or on oolitic limestone in Gloucestershire. Nowadays, it is often most prominent on steep slopes where the roots of larger forest trees cannot maintain those species on the shallow soils (Staples 1970; Wigginton 1999).

Box has a reputation for long persistence after plantation (deliberate or bird-sown) in woods and slope thickets, estate pleasure grounds and gardens and it may also occur in hedges or in other shady sites near habitation after 'jumping the garden wall'. Box can also survive and establish as a discard from cultivation, often dumped in less appropriate waste or derelict ground habitats, but also surviving in long abandoned gardens or in other neglected, unmanaged ground around ruins. Since Roman times, Box has been a traditional hedging and topiary subject and, in a dwarf form, it remains a very popular edging plant for beds in both decorative and kitchen gardens.

Flowering reproduction

Although it will flower when not in deep shade and does so early in the year in April or May, the blossom is small, yellowish green and insignificant in appearance, attracting little attention. Each small cluster in a leaf axil contains both male and female flowers, usually 5-8 males and a solitary female. Pollination involves insect visitors and the subsequent fruit does not ripen until October. The fruit is an ovoid, white, papery capsule or pod containing up to six shiny, hard, black seeds that are released explosively when it eventually splits (Edlin 1964; Sell & Murrell 2009). Each seed possesses an elaiosome or nutritive oil body in the form of a caruncle, developed from the lips of the ovule micropyle. The food body attracts ants which assist local dispersal of the seed, although this is only active and positive over a few metres at most (Ridley 1930, p. 524). Only vigorous bushes in the more open parts of woods or gardens produce viable seed (Pigott & Walters 1953).

British and Irish occurrence

As mentioned above, B. sempervirens is considered native in just ten sites scattered across S England. For instance, in parts of Berkshire (VC 22), Box stands appear to be well grown and are said to often give rise to self-sown individuals (Crawley 2005). However, seed production in Ireland at least is poor, so that self-sown seedlings are rare or very rare, with only eight sites from four VCs listed in Cat Alien Pl Ir, in Cos Waterford (H6), Cavan (H30), Tyrone (H37) and Armagh (H38). The New Atlas hectad map, in comparison, plots records of the most recent date class (1987-99) from 14 Irish VCs. Three of the four Co Tyrone records are associated with major landed estates in the VC where the plant is undoubtedly planted (McNeill 2010) and all eight records from Co Wexford are of planted sites, the majority from around ruins of past habitation (Green 2008).

Fermanagh occurrence

There are just six widely scattered Fermanagh stations for B. sempervirens. In addition to the first record above, the details are: lane approaching cliffs, Tiranagher Beg Td, 24 April 1994, RHN & RSF; Druminiskill, 26 April 1995, RHN; Old Crom Castle, 3 July 1995, RHN & RMHN; Bigwood Td, Lower Lough Erne, 13 August 1996, RHN, RSF & Don Cotton; Kilcoo Crossroads, 4.5 km SE of Garrison, 8 September 2010, RHN & HJN.

European and world occurrence

B. sempervirens is regarded as a member of the Sub-Mediterranean-Sub-Atlantic biogeographical element and is considered native in SW & WC Europe and in the mountains of NW Africa (Sell & Murrell 2009). It is widely cultivated and naturalised beyond its native range (T.D. Dines, In: Preston et al. 2002).

Toxicity

All parts of the plant are EXTREMELY POISONOUS, containing a complex group of steroidal alkaloids. The plant gives off a disagreeable smell and has a bitter taste, so fortunately animals avoid it. Horses and other large stock animals have died of respiratory failure after browsing it or eating clippings (as little as 750 g of consumed foliage is sufficient to kill a horse) (Cooper & Johnson 1998).

Threats

None.