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Castanea sativa Mill., Sweet Chestnut

Account Summary

Introduced, neophyte, deliberately planted and rare or very occasional. European temperate, also cultivated and widely naturalised in Europe.

17 September 1986; McMullin, A.S. & Corbett, P.; Mullynacoagh Td shore, Upper Lough Erne.

January to November.

Growth form and preferred habitats

This is potentially a very large deciduous tree, up to 30 m with a wide, broad crown. Older trees have deeply fissured bark on the trunk, the longitudinal fissures often spirally curved, allowing the species to be easily recognised at any time of year. Ecologically, C. sativa can tolerate most soils, although it thrives best on moist, acidic, sandy ones (T.D. Dines, in: Preston et al. 2002). In season, the leaf canopy casts a heavy shade, while the deep, persistent leaf-litter creates a mor humus, often with a pH of 4 or under (Rackham 1980, p. 332). In Fermanagh, conspicuous, distinctive and often very large old trees of this species are almost always associated with parkland or tree collections (arboreta) in landed estates such as Castle Coole, Crom or Colebrooke. Unlike the quasi-native chestnut woods in Kent, E Essex and SE Suffolk described by Rackham (1980, pp. 332-9) which are or were coppiced every 12-14 years for small timber, in Ireland C. sativa never formed woodland stands. A possible reason for this is the more recent date of introduction and plantation of the tree in Ireland, probably sometime before the 17th century – although nobody really knows a definite date (Nelson & Walsh 1993, p. 105).

Flowering reproduction

Trees flowering in June and July, the minute flowers being borne on long catkins held erect at the tips of shoots. Individual catkins are 10-20 cm long, with female flowers at their base and more numerous male flowers on the remainder of the catkin length. Various insects pollinate the flowers and the characteristic prickle-covered green chestnuts develop until the autumn. In most of Ireland, the vast majority of ovules abort and it is doubtful if any of the chestnuts produced in northern counties are fertile and capable of germination as self-sown trees are very rare or totally absent. I expect that the partially developed chestnuts are eaten by birds and small mammals as they do not seem to accumulate, and in my experience they quickly are taken.

European region of origin

C. sativa is a native species of the more humid areas of eastern Mediterranean countries. However, selected cultivated forms, some of them grafted with superior fruiting scions, have long since been introduced into more northerly regions of Europe, and the tree and its edible nuts and other products has been present in Britain since Roman times (Zohary & Hopf 2000, p. 189). Despite the familiar 18th century English common name 'Spanish Chestnut' and the present day frequency of the tree in the Pyrenees, the species is unlikely to be native as far west as Spain (Rackham 1980, p. 329). The native range of C. sativa is controversial. The editors of Flora Europaea took a conservative view, regarding it as indigenous in the Balkans (Albania, Greece, Jugoslavia) and Turkey, and less probably in SC Europe (Tutin et al. 1993). It is common in Italy as well as in southern France and Calabria, where it is extensively coppiced (Rackham 1980, p. 332).

British and Irish occurrence

The New Atlas hectad map demonstrates that C. sativa is much more thinly scattered in Ireland than in Britain, and especially so when compared to S England and Wales. The tree flowers and fruits readily, and in suitable, warmer conditions in S England, if not elsewhere at present, the nuts germinate in the spring after their production. Unlike Beech and Oaks, losses due to seed predation appear rare in England. As it cannot regenerate under its own shade, transport of the large seed into gaps, or to sites under other tree species is necessary, the most likely vectors being rooks (Rackham 1980, pp. 334-5).

Fermanagh occurrence

This is a rare or very occasional tree in Fermanagh, having only been recorded in 15 tetrads, 2.8% of those in the VC. It is confined to estate parks and woodland plantations, plus a few outliers nearby. Only one or two of the records occur on the margins of the demesnes mentioned above and, although I greatly doubt it, these might just be self-sown trees. However, in all our years of field recording RHN and I have never found either seedlings or saplings of Sweet Chestnut anywhere in Fermanagh.

In truth, the reproductive biology and local behaviour of the exotic (ie non-native) trees and shrubs in N Ireland have had almost no attention paid to them. In many cases, it is not known whether they can successfully set seed, disperse and establish in this part of the world, as many of them undoubtedly do in S England (T.D. Dines, in: Preston et al. 2002).

A well-known English tree expert, the late Alan Mitchell, suggested that only a few exotic, introduced trees "plant themselves" in Britain and Ireland. He highlighted one very obvious exception 'that proves the rule', as Acer pseudoplatanus L. (Sycamore). Mitchell went on to list Sweet Chestnut along with several introduced conifers that he believed could produce natural seedlings, although he reckoned these were likely to be "very local" (A. Mitchell, in: Milner 1992, p. 158).

In Fermanagh, as elsewhere, in the autumn it is certainly possible to find shiny chestnuts inside the leathery, green or brown, heavily-spined husks which split into four valves beneath the tree. However, it is very doubtful if they contain viable seed in Ireland as far north as Fermanagh. This contrasts with the situation in Essex and Kent where Rackham (1980) found C. sativa regenerating successfully, and probably even capable of invading woodland of other species. A study of the ability of exotic, non-native trees to regenerate or not, would be another example of a feasible school project, where a very little study could fill a gap in our knowledge regarding the performance and the local behaviour of long-introduced plants.

Uses

The tree is valued for its nut crop. For many generations it formed an important part of the traditional diet of farming communities, and it was also fed to stock animals.

Names

In S England, Sweet Chestnut survived throughout the Dark Ages, and acquired an Anglo-Saxon name, 'cyst' or 'cisten', the latter form (pronounced 'chisten'), being a derived survival from the Classical Latin name, 'Castanea'. The tree name then made the transition to a word element in at least a few English place names, for instance, 'Cystewde' of 1272, which is today's 'Chest Wood' near Colchester (Rackham 1980, p. 330).

Threats

None.