Northern Ireland's Priority Species

Cirsium heterophyllum – melancholy thistle

 

Distribution map

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Cirsium heterophyllum (L.) Hill
Family: Asteraceae

This tall, large-leaved, almost prickle-free thistle of moist hay meadows and grassy river banks is a widespread but declining native perennial in most upland areas of northern Britain and is also scattered as far south as mid-Wales. Despite the high frequency of the plant in Great Britain it was not recorded in Ireland until 1949, when it was discovered growing by the Roogagh River in western Fermanagh. Melancholy thistle persists in this original Irish station, but has also been fleetingly reported (sometimes possibly erroneously), in other scattered locations in Northern Ireland during the last twenty years.

In brief

  • Probably confined to moist grassland in County Fermanagh where it was first discovered in 1949

  • The pattern of C. heterophyllum occurrence in a few widely-spaced stations in the north of Ireland is a characteristic shared by several other species of the Eurosiberian Boreal-montane geographical element occurring in the flora of Britain and Ireland. The best examples for comparison are Geranium sylvaticum , wood crane's-bill and Pyrola media , intermediate wintergreen

  • In Britain the species most often frequents calcareous or base-rich soils at altitudes between 90m and 975m above sea level, rather than in lowland situations. Despite this it is not really a 'calcicole' (that is, lime-loving species), but rather appears to grow equally well on a wide range of soils, provided adequate moisture is available

  • Initially when it flowers in July and August the heavyweight terminal flower heads droop sideways, looking rather sad on their tall, slender, white-haired stems. The melancholy appearance gave rise by the 'Doctrine of Signatures' to the herbalist use of the plant to treat depression (Grigson, 1987)

  • When mature, the large, red-purple flower heads do not droop but are held completely upright. They are visited by bees

  • Extreme rarity and isolation of a population is always a threat in itself to long-term survival of a species, making a species such as melancholy thistle more vulnerable to chance environmental damage.

Species description
The basal leaves of this perennial are very large indeed (up to 40cm long and 8cm wide), long-stalked, elliptic lanceolate, finely toothed but like the rest of the plant, not armed with spines to deter grazing animals. The leaves are heavily felted with fluffy, cottony, white hairs beneath. The flower head, usually solitary, but occasionally forming terminal clusters of 2 to 4, is borne on a bare, spineless, erect stem, and is around 3.5cm in diameter.

Life cycle
Melancholy thistle is stoloniferous and the spreading stems grow vegetatively to form clusters of the plant. In the Fermanagh population, each year many of the plants do not flower, but remain vegetative. In August the fruits are topped with a long white pappus of hairs, which like the dandelion help wind-disperse the seed.

Similar species
The only similar thistle is meadow thistle Cirsuim dissectum . The leaves of melancholy thistle are heavily felted with fluffy, cottony, white hairs beneath, so that even in the vegetative state it could not readily be mistaken for meadow thistle. The flower head of melancholy thistle is also several times bigger than that of meadow thistle, again making it unmistakable (Clapham et al. , 1987).

How to see this species
The site on which it grows in Fermanagh is privately owned. The best alternative for seeing the plant in flower is to visit northern England in mid summer. It is plentiful, for example, in the Malham limestone area of Yorkshire. In Britain, the species most often frequents calcareous or base-rich soils at altitudes between 90m and 975m above sea level, rather than in lowland situations. Despite this, it is not really a 'calcicole' (lime-loving) species, but rather appears to grow equally well on a wide range of soils, provided adequate moisture is available. Relevant access permissions should always be sought prior to visiting any sites.

Current status
Melancholy thistle was not recorded in Ireland until 1949, when it was discovered growing by the Roogagh River in western Fermanagh. Melancholy thistle persists in this original Irish station, but has also been fleetingly reported (sometimes possibly erroneously), in other scattered locations in Northern Ireland during the last twenty years. A further Fermanagh record has recently come to light from July 1976 when it was recorded in the north of the county, east of Formil forest, 'a stand of about 100 plants near a group of marsh thistle, C. palustre in a drier part of a section of wet, cut-over bog'. No voucher specimen appears to exist and it requires confirmation before it can be accepted wholeheartedly.

A couple of apparently casual occurrences of melancholy thistle have been recorded elsewhere in Ireland. One of these was by a roadside near Lough Gill in County Leitrim recorded in 1962 by the famous Scottish botanist Mary McCallum Webster. No mention of this site occurs in the Irish Red Data book of vascular plants (Curtis and McGough, 1988), and we presume it has not persisted or been refound. Another record dated 1996 exists on the Armagh side of the Fermanagh boundary near Fivemiletown, but this is regarded as planted or a garden escape.

Melancholy thistle is listed in Schedule 8, Part 1 of the Wildlife (Northern Ireland) Order 1985, which gives it special protection.

Why is this species a priority in Northern Ireland?

  • This species is rare with Northern Ireland being the stronghold in Ireland.

Threats/Causes of decline
Extreme rarity and isolation of a population is always a threat in itself to long-term survival of a species, making it more vulnerable to chance environmental damage. Essentially a hay-meadow species, it is sensitive to grazing pressure and to excessive or too-early season mowing preventing seeding. Nutrient enrichment or drainage might also oust the species due to increased competition from vigorous rival species.

Conservation of this species

Current action

  • The landowner of the Fermanagh grasslands at Roogagh maintains a regime of cutting and grazing that allows the species to persist.

Proposed objectives/actions

  • Maintain the viable population of this species.

What you can do
Records of new sites and estimates or counts of the sizes of populations are always valuable. Send information (including photographs, if obtained). Send to: The Botanical Society of the British Isles – c/o Botany Department, National Museums Northern Ireland, 153 Bangor Road, Cultra, Co. Down, BT18 0EU or to CEDaR, National Museums Northern Ireland, 153 Bangor Road, Cultra, Co. Down, BT18 0EU, Tel: 028 9039 5256, cedar.info [at] magni.org.uk.

Further information

Links
Flora of Northern Ireland

Literature
Clapham, A.R., Tutin, T.G. and Moore, D.M. (1987). Flora of the British Isles . 3rd edition. Cambridge University Press, Cambridge.

Grigson, G. (1987). An Englishman's Flora . Facsimile of the Dent 1955 edition. Phoenix House, London.

Text written by:
Dr Ralph Forbes