A biennial or short-lived perennial herb of glades in or margins of deciduous woodland, usually Fagus or Quercus; sometimes also occurring in hedge banks. It is found mainly on calcareous, freely-draining, loamy soils. Lowland.
The marked decline of this species before 1930 was shown in the 1962 Atlas. The reasons for it are unclear, but it may be more apparent than real as many old records appear to have been of transient populations. Further sites have been lost since 1930, but the great storm of 1987 opened up its woodland habitats, and since then huge populations have been recorded in Surrey.
European Temperate element, with a continental distribution in W. Europe.
Count of 10km squares in Great Britain: 50
Count of 10km squares in Ireland: 0
Count of 10km squares in the Channel Isles: 0
Atlas Change Index: -0.52
RDB Species Accounts
Cynoglossum germanicum Jacq. (Boraginaceae)
Green hound's-tongue, Tafod y Bytheiad Gwyrdd-Ddail
Status in Britain: VULNERABLE. WCA Schedule 8.
Status in Europe: Not threatened.
C. germanicum is native in glades in deciduous woodlands usually in hilly regions. It is persistent in these sites as, for example, in the beech woods of Norbury Park in Surrey, where it has been plentiful since the seventeenth century (Merrett 1666), but the actual populations, varying from a few to several hundred plants, shift about as gaps in the canopy open and gradually close over. Similar localities occur nearby on White Hill, where this species is known to have persisted for 50 to 150 years.
In Surrey the species grows most vigorously and abundantly on moist, freely draining, shallow loamy soils over chalk. The tree canopy is dominated by beech, with ash, sycamore and field maple in the gaps and yew under the main canopy. The ground may be almost bare or with patches of Mercurialis perennis, but dense M. perennis can shade out the first year rosettes of C. germanicum. Other typical associates include Arum maculatum, Brachypodium sylvaticum, Circaea lutetiana, Daphne laureola, Geum urbanum, Rubus vestitus and Viola reichenbachiana. It has, however, become extinct in a few localities of this type, probably because of changes in the woodlands such as cessation of coppicing or conversion to uniform-aged plantation. C. germanicum has also colonised sites which are clearly man-made. Three of its remaining localities are in oak woodlands, where it grows besides roads or tracks which contain, at least in their foundations, lime-rich materials (chalk, hard limestone or concrete) but the natural soil is acid and has been shown experimentally to be unsuitable. Many of its old records seem to have been transient where the species was acting almost as a wayside weed. It appears frequently but briefly in such sites around its main localities in Surrey. At the Oxfordshire site, C. germanicum grows in mixed deciduous, mainly oak-ash woodland with Brachypodium sylvaticum, Galium aparine, Geranium robertianum, Glechoma hederacea and Urtica dioica.
Surrey has long been the stronghold for this species in Britain, where several thousand plants were recorded at some sites in good years. The 1987 storm created much open ground, and since then the plant has been recorded at numerous locations in fourteen 1 km squares, mostly in woods around Mickleham. In 1997, an estimated 130,000 plants were recorded. Outside Surrey it appears to be extant at only three sites, one each in Gloucestershire, Oxfordshire and Kent. In Gloucestershire, the population is very small, with only 20-33 plants occurring between 1977 and 1987 (Taylor 1990a), and 33 in 1989 and 1993 (I.Taylor, pers. comm.). The Oxfordshire site held at least 200 plants in 1985, but only about twenty in 1994. C. germanicum has not been seen for several years at a second site in Oxfordshire which held several hundred plants in the 1950s and 100 in 1980 (Everett 1988). The small colony in Kent was established from deliberately sown seed (Rose 1960), and has persisted for 40 years.
C. germanicum is a biennial or sometimes a short-lived perennial, and the dark green glossy rosettes persist through the winter when the shoots of Mercurialis perennis have died down. The winter leaves maintain low rates of photosynthesis in mild weather and thus benefit from the leafless state of the tree canopy. The leaves are poisonous (Mattocks & Pigott 1990) and are avoided by deer, rabbits and molluscs, but young plants are defoliated by bank voles. The large rosettes develop a thick tap-root, then flower freely in the second summer and set abundant fruit. Much of the fruit remains on the shoots for many months and is not distributed. Beside paths, however, it is carried away by larger mammals including man and dogs. In fine hair and on woollen clothing the fruits tangle and are probably lost from the whole area. On coarse hair, particularly that of roe deer, the fruits become attached but are easily detached. The great increase in the roe deer population in the last 30-50 years has resulted in the appearance of many new colonies of C. germanicum in central Surrey and an explosive spread after the storm of 1987.
Seeds require several weeks of low temperature before they germinate in early spring, but they then have no dormancy in most conditions beyond the first year. This is a key factor in the ecology of the species. In contrast to most species of glades, seeds of C. germanicum do not lie dormant in the soil. When a gap is created, fruits must be transported into it, and the probability of this occurring depends on the surrounding abundance of the species. Once the overall population becomes restricted, the chance of dispersal into gaps decreases and eventually, as the woodland changes, the species dies out. Such small populations can be maintained only artificially.
Outside Britain, it occurs in France and Germany, and in the deciduous woodland zone of the mountains of southern-central Europe. It is rare and declining in several countries.
C. D. Pigott
PLANTATT - Attributes of British and Irish plants. (.zip 1455KB) This dataset was compiled and published in 2004, and last updated in November 2008. Download includes an Excel spreadsheet of the attributes, and a PDF explaining the background and nomenclature. Note that the PDF version is the booklet as published, whereas the Excel spreadsheet incorporates subsequent corrections. A hardcopy can be purchased from the Centre for Ecology and Hydrology.