A pseudobulbous herb of boggy areas where the water is usually acidic but subject to some lateral movement. Typically it grows amongst saturated Sphagnum, but also on peaty mud and among grasses on the edges of runnels and flushes. 0-500 m (Llyn Anafon, Caerns.).
Drainage of bogs, particularly in the lowlands, has caused a dramatic decline of this species, especially before 1930. Overgrazing may have caused losses in the uplands. It is inconspicuous and under-recorded in some areas; intensive searches in others have shown it to be more frequent than previously thought.
Circumpolar Boreal-montane element, with a disjunct distribution.
Light (Ellenberg): 9
Moisture (Ellenberg): 9
Reaction (Ellenberg): 2
Nitrogen (Ellenberg): 1
Salt Tolerance (Ellenberg): 0
January Mean Temperature (Celsius): 2.9
July Mean Temperature (Celsius): 13.3
Annual Precipitation (mm): 1615
Height (cm): 8
Perennation - primary
Life Form - primary
Clonality - primary
Clonality - secondary
Count of 10km squares in Great Britain: 302
Count of 10km squares in Ireland: 44
Count of 10km squares in the Channel Isles: 0
Atlas Change Index: -0.32
Scarce Atlas Account
Hammarbya paludosa (L.) Kuntze
H. paludosa is found in boggy areas where the drainage water is moderately acidic. It frequently grows in sphagnum and can also be found on peaty mud and among grasses on the edges of runnels. In most sites it is associated with some water movement. Associated species are numerous but often include Carex echinata, Drosera rotundifolia, Erica tetralix, Molinia caerulea, Nardus stricta and Rhynchospora alba. In some sites Vaccinium oxycoccos is quite frequent. In Merioneth, and perhaps elsewhere, it tends to occur where bogs are flushed with water from base-rich rocks, growing with base-demanding sphagna such as S. contortum, S. teres and S. warnstorfii. H. paludosa is generally a lowland species, though it has been recorded up to 500 metres on Millfore and at Llyn Anafon.
H. paludosa is a perennial with a long flowering season: there may be plants in flower in one colony from the end of June until the second half of September. Though seed is often set, this species also reproduces vegetatively by means of bulbils which develop on the leaf tips and which, having become detached, develop into new plants (Summerhayes, 1951).
The drainage of bogs has brought about a dramatic decrease in the number of recorded sites, especially in lowland England. In lowland mires systems such as the New Forest the species depends on grazing to maintain open runnels, flushes and Molina-free mires in which it grows. The tiny, shallow-rooted plants are vulnerable to nearby trampling which can cause them to pop out of the ground. However, there are many areas in Scotland where H. paludosa could well be thriving unseen. More sites arc known in Cumbria, for example, than at any time in the past simply as a result of recent intensive recording.
H. paludosa is most frequent in northern and central Europe, but it is also recorded at scattered localities in the boreal zone of Asia and North America. It is considered to be under threat in Europe as a whole.
Because of its small stature (sometimes under 3 cm in height), sporadic appearance and pale coloration, H. paludosa is notoriously difficult to find and may often escape detection. It could well be holding its own in the more western and northern parts of Great Britain.
M. S. Porter
Atlas text references
Allan & Wood (1993)
1988. The Irish Red Data Book. 1. Vascular Plants.
1986. Atlas of north European vascular plants north of the Tropic of Cancer. 3 vols.
1965. Vergleichende Chorologie der zentraleuropäischen Flora. Volume 1. 2 vols.
1994. Scarce plants in Britain.