A tufted perennial herb of damp, ungrazed mountain ledges, wet, shaded gullies and the sides of gills and streams. In Scotland it sometimes descends to near sea level along streams, but usually occurs above 150 m, reaching 1190 m on Ben Lawers (Mid Perth).
There has been no change in distribution of O. digyna since the 1962 Atlas, and it is probably still present in many of the more remote 10-km squares in Scotland for which there are only pre-1970 records.
Circumpolar Arctic-montane element.
Light (Ellenberg): 7
Moisture (Ellenberg): 6
Reaction (Ellenberg): 5
Nitrogen (Ellenberg): 3
Salt Tolerance (Ellenberg): 0
January Mean Temperature (Celsius): 1.7
July Mean Temperature (Celsius): 12.1
Annual Precipitation (mm): 1940
Height (cm): 30
Perennation - primary
Life Form - primary
Clonality - primary
Count of 10km squares in Great Britain: 311
Count of 10km squares in Ireland: 24
Count of 10km squares in the Channel Isles: 0
Atlas Change Index: -0.71
Weighted Changed Factor: -18
Weighted Change Factor Confidence (90%)
Atlas text references
1986. Atlas of north European vascular plants north of the Tropic of Cancer. 3 vols.
Jalas & Suominen (1979)
1981. Docks and knotweeds of the British Isles. Botanical Society of the British Isles Handbook no. 3.
1965. Vergleichende Chorologie der zentraleuropäischen Flora. Volume 1. 2 vols.