A mycorrhizal, evergreen perennial herb, spreading by rhizomes within leaf litter and bryophytes in ericaceous dwarf shrub communities of old pine plantations, rarely now in native Pinus sylvestris forests. The solitary flower is insect-pollinated, but recruitment from seed is rare and most propagation is vegetative. Lowland, reaching 300 m (Castle Grant, Moray).
Diminished by past collection, this attractive species has continued to decline through changes in land use and forest management. Much of this decline took place before 1970, but its future is dependent on sympathetic management. Most remaining populations are small and vulnerable.
Circumpolar Boreal-montane element.
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Light (Ellenberg): 4
Moisture (Ellenberg): 5
Reaction (Ellenberg): 4
Nitrogen (Ellenberg): 1
Salt Tolerance (Ellenberg): 0
January Mean Temperature (Celsius): 2
July Mean Temperature (Celsius): 13
Annual Precipitation (mm): 985
Height (cm): 4
Perennation - primary
Life Form - primary
Comment on Life Form
Clonality - primary
Count of 10km squares in Great Britain: 27
Count of 10km squares in Ireland: 0
Count of 10km squares in the Channel Isles: 0
Atlas Change Index: 0.14
Plantatt Conservation Status
RDB Species Accounts
Moneses uniflora (L.) Gray (Pyrolaceae)
One-flowered wintergreen, Glas-luibh Chùbhraidh
Status in Britain: VULNERABLE.
Status in Europe: Not threatened.
In Britain, M. uniflora is the rarest herb of pinewoods. It is predominantly a plant of the north-eastern Scottish pinewoods, although nearly all known populations occur in old established plantations rather than in the remaining fragments of native pine forest. Within the forest, M. uniflora is restricted to the most humid areas of the forest floor, rosettes being found within the moist bryophyte and litter layers. The field layer is usually a mosaic of dwarf shrubs which include Calluna vulgaris, Empetrum nigrum, Vaccinium myrtillus and V. vitis-idaea, one or other of which may be locally dominant. Besides these, the main constants are Deschampsia flexuosa and a range of common bryophytes, chiefly Dicranum scoparium, Hylocomium splendens, Pleurozium schreberi, Rhytidiadelphus loreus, R. triquetrus, and the less common Ptilium cristacastrensis. Among the associated herbs are Galium saxatile, Luzula multiflora, Potentilla erecta and Trientalis europaea, and Linnaea borealis accompanies it at a few localities. One colony of M. uniflora occurs in a sparsely wooded mire where the vegetation is dominated by Calluna vulgaris, Erica tetralix and Molinia caerulea. However, in that site M. uniflora does not appear to be very healthy, displays leaf chlorosis (not seen at any other of its sites), and is probably at the limit of its wetness tolerance.
This plant is a clonal, wintergreen herb, flowering between June and August. It spreads within the forest mainly by a network of fine, branching roots, but the production of dust-like seed provides opportunities for long distance dispersal. It is highly adapted to the nutrient-poor shaded conditions of the forest floor: its wintergreen habit allows it to photosynthesise in all seasons and in low light conditions. Unlike closely related members of the Pyrolaceae such as Orthilia secunda and Pyrola species which possess rhizomes, M. uniflora lacks such storage organs and relies on a regular and continuous supply of nutrients via its mycorrhizal associates.
M. uniflora has undoubtedly suffered a significant decline since its discovery in 1792. It is extant in three vice-counties but has formerly been recorded from nine, with doubtful records from a further three. The centre of its distribution is in Moray, and it reaches furthest west in Strathfarrar and Glen Affric. Some 80-90% of the British population, of many thousands of rosettes, occurs in one site. Most of the other populations are small, ranging from fewer than 50 rosettes, to a few hundreds.
Historically, collecting has had a major impact on its distribution and abundance, but during this century, changes in land use and land management have become the major causes for concern. The restriction and adaptation to the conditions of the coniferous forest floor microhabitat renders M. uniflora extremely vulnerable to large-scale disturbance. The plant is threatened by any activity that causes widespread disruption of the forest ground-layer resulting in increased dryness and higher light levels. Further, because of its heavy dependence on mycorrhizae for nutrition, any factor that causes a decline in the health of its fungal associates will also lead to a decline in the health of M. uniflora. The establishment of forest plantations has evidently provided areas for colonisation in the past, but modern harvesting by large-scale clear-felling could destroy many of the small extant populations. The continued survival of M. uniflora is highly dependent upon effective communication between conservationists, foresters and forest managers, not least because of the difficulty in locating the plant. Ex situ conservation is not an option at present because M. uniflora is extremely difficult to propagate in cultivation.
M. uniflora has a circumboreal distribution with its main centre in north-central Europe and Scandinavia. On the American continent it extends south to near Mexico City and in Asia it reaches the Lashai Hills of India. Little variation occurs in this monospecific genus, but one apparently poorly-differentiated variety, var. reticulata (Nutt.) Blake, has been recognised on the American Pacific coast.
P. S. Lusby
Atlas text references
1986. Atlas of north European vascular plants north of the Tropic of Cancer. 3 vols.
1978. Vergleichende Chorologie der zentraleuropäischen Flora. Volume 2. 2 vols.
1999. British Red Data Books. 1. Vascular plants, edn 3.
1999. The past and present status of Moneses uniflora (L.) Gray (Pyrolaceae) in Scotland. Watsonia. 22:343-352.