A perennial herb with creeping woody stems occurring in chalk and limestone districts in two distinct habitats. Inland, it grows in woodland edges and rides, and on lanesides and banks in partial shade. On the coast, it is found amongst naturally dwarfed, open scrub on slumped cliffs, slopes and crags. It spreads by seed and from the stems rooting at nodes. It also occurs as a garden escape on roadsides and waste ground. Lowland.
The native distribution of this species seems to have been more or less stable since 1930, though some populations have been shaded out in neglected or unmanaged woodland. It has increased as an alien since the 1962 Atlas.
European Southern-temperate element.
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Light (Ellenberg): 5
Moisture (Ellenberg): 4
Reaction (Ellenberg): 7
Nitrogen (Ellenberg): 4
Salt Tolerance (Ellenberg): 0
January Mean Temperature (Celsius): 4.8
July Mean Temperature (Celsius): 16.3
Annual Precipitation (mm): 941
Height (cm): 60
Perennation - primary
Life Form - primary
Life Form - secondary
Comment on Life Form
Clonality - primary
Count of 10km squares in Great Britain: 25
Count of 10km squares in Ireland: 0
Count of 10km squares in the Channel Isles: 0
Atlas Change Index: -0.33
RDB Species Accounts
Lithospermum purpureocaeruleum L. (Boraginaceae)
Buglossoides purpureocaeruleum (L.) I. M. Johnston
Purple gromwell, Maenhad Gwyrddlas
Status in Britain: LOWER RISK - Near Threatened.
Status in Europe: Not threatened.
This plant of limestone and chalk occurs in two distinct habitats, though is principally a plant of woodland edges and rides, and of lanesides and banks in partial shade. It maintains vigorous growth where there is some protection afforded by other vegetation as, for instance, in open bushy areas or under a light coppice canopy, but it becomes weak in deep shade. Common associates include Arum maculatum, Brachypodium sylvaticum, Geum urbanum, Hedera helix, Ligustrum vulgare, Melica uniflora, Mercurialis perennis and Rubia peregrina. In Glamorgan it occurs mainly along the coast on slumped limestone cliffs, slopes and crags. In these places, it usually occurs in lightly-grazed or ungrazed naturally-dwarfed scrubby vegetation dominated by Cornus sanguinea, Crataegus monogyna, Ligustrum vulgare, Prunus spinosa or Ulex europaeus, which provide protection without too much overshading. Devon populations are in similar habitats on a chalk undercliff.
L. purpureocaeruleum is a rhizomatous perennial, flowering mainly in May, but extending into June, and readily producing seed. Decumbent non-flowering stems may root where they touch the ground, and provide another means of vegetative reproduction.
An area of wooded limestone ridges, bounded by Cheddar, Weston-super-Mare and Bristol, was historically considered to be the most important area for this species, encompassing the largest number of sites. L. purpureocaeruleum still occurs in about twenty of them, though in many the populations are now small and vulnerable. Elsewhere, the plant occurs at four sites in Devon, about eight in Glamorgan, and one in Denbighshire. Most of the Glamorgan sites have strong populations of many thousands of plants, as do the Devon coastal sites. In Denbighshire, the tiny colony, covering only a few square metres, may represent a number of independent plants, or a single one with inter-connected creeping stems (Evans & Ellis 1994b). It formerly occurred as a native plant in Kent, and has been recorded as a casual in a few places.
L. purpureocaeruleum has declined in recent years in Somerset, and colonies remain much threatened locally by changes in woodland management. In the past, regular coppicing of Corylus avellana, Fraxinus excelsior and Tilia cordata provided the necessary light for strong growth and flowering. Many woods are now overgrown and neglected, and have an impoverished ground flora. Plants of L. purpureocaeruleum may survive in a weak or depauperate vegetative state for many years under a fairly dense canopy, but will eventually succumb. Revitalisation of woodland populations should be a high conservation priority. The strong coastal colonies do not appear significantly threatened.
It is mainly a plant of southern and central Europe, common in the Balkans and Iberia, extending northwards to Britain and Poland (rare in both countries), and eastwards to the Caucasus and the Lake Baikal area.
M. J. Wigginton