An evergreen, procumbent perennial herb of heaths and moors, where it typically grows on well-drained, sandy, often skeletal soils in dwarf Calluna heath. In Scotland its sites are usually Calluna-Arctostaphylos heath. Between 270 m (Canisp, W. Sutherland) and 960 m (Lochnagar, S. Aberdeen).
The map shows only confirmed records, as many old records are based on abnormal D. alpinum. Burning and grazing of heaths may have caused the extinction of D. complanatum in lowland England but it may be under-recorded in montane areas.
Circumpolar Boreal-montane element, with a continental distribution in western Europe.
Light (Ellenberg): 6
Moisture (Ellenberg): 4
Reaction (Ellenberg): 1
Nitrogen (Ellenberg): 2
Salt Tolerance (Ellenberg): 0
January Mean Temperature (Celsius): 1
July Mean Temperature (Celsius): 12.5
Annual Precipitation (mm): 1465
Count of 10km squares in Great Britain: 10
Count of 10km squares in Ireland: 0
Count of 10km squares in the Channel Isles: 0
RDB Species Accounts
NOTE: The account below is for the sub-species. Closely related species and sub-species may have separate accounts listed elsewhere in the Online New Atlas
Diphasiastrum issleri (Rouy) J.Holub (Lycopodiaceae)
Diphasiastrum complanatum ssp. issleri (Rouy) Jermy, Lycopodium issleri (Rouy) Domin
Yellow cypress clubmoss
Status in Britain: LOWER RISK - Near Threatened.
Status in Europe: Not threatened.
This taxon is found on mountainsides in rather open communities of dwarf shrubs on shallow skeletal soils over acid country rock. It is usually associated with shrubby Arctostaphylos alpinus, Calluna vulgaris, Vaccinium myrtillus, V. vitis-idaea together with Molinia caerulea, and occasionally Diphasiastrum alpinum.
Although some spore abortion has been recorded, many fertile spores are formed and there is no biological reason why the species cannot spread naturally.
Its early records in Britain (in 1866) were from lowland heath at Bramshott, Hampshire, later to be found in Worcestershire and, in 1881, at Woodchester Park, Gloucestershire. It has long since disappeared from these sites along with the habitat. The Woodchester plant was described by Boswell-Syme (as var. decipiens) and botanists such as Edward Marshall began recording the variety from dwarf shrub heaths on Scottish mountains. For the next fifty years the taxon was taken to be a form of D. alpinum and not recorded until A.G.Kenneth discovered a fine colony on Canisp, West Sutherland. Others found it in Strath Nethy and Glen Quoich in the Cairngorms (Jermy 1989). D. issleri was re-found in 1991 on Geal Charn, above Glen Feshie, nearly a hundred years after it was first recorded there by J.A.Wheldon and A.Wilson, and at the 810 metre altitude originally recorded.
The presence of this plant in Britain has been well documented because of its taxonomic interest, and around which there is still some nomenclatural uncertainty. It appears to be intermediate between D. alpinum and D. complanatum, and may have arisen through hybridisation of those species (Jermy & Camus 1991). Whatever its origin the same taxon is found across central Europe from central France to the Czech Republic and Poland.
The known sites in Britain, especially those above 600 metres, are unlikely to be burnt and no special conservation efforts are needed. The lowland sites have long since changed in character or disappeared completely.
A. C. Jermy
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.
Atlas text references
1986. Atlas of north European vascular plants north of the Tropic of Cancer. 3 vols.
Jalas & Suominen (1972)
1989. The history of Diphasiastrum issleri (Lycopodiaceae) in Britain and a review of its taxonomic status. Fern Gazette. 13:257-265.
1978. Ferns and their allies. The Island of Mull: a survey of its flora and environment. :12.1-12.7.
1965. Vergleichende Chorologie der zentraleuropäischen Flora. Volume 1. 2 vols.
1997. The ferns of Britain and Ireland, edn 2.
1999. British Red Data Books. 1. Vascular plants, edn 3.