 | | Cirsium palustre in bloom, Saaremaa, Estonia fen meadow |  |
Marsh Thistle
Cirsium palustre
C. Michael Hogan PhD
October 16, 2009
Cirsium palustre is a beautiful clustered head thistle, although unpalatable for livestock. Its modern distribution and habitat appears to be a consequence of the post-Neolithic evolution of human agriculture from Siberia to the British Isles, since it is well adapted to marshy soils not conducive to intensive agriculture, but it and its characteristic associates thrive in management schemes varying from low intensity grazing to occasional mowing and alternating neglect. Its vast seedbank yields only a fraction of germinating seeds per year, providing a long term reservoir of future individuals. While this herbaceous species is not threatened, the damp habitats which it inhabits are in ongoing danger of fragmentation, jeopardising the survival of many rarer associates that are within these fen meadow ecosystems. C. palustre is a monocarpic species, whose seeds are chiefly wind dispersed.
DISTRIBUTION
C. palustre occurs from Lake Baikal in Siberia west to the Baltics and Scandinavia and south through Eastern Europe and as far southwest as the Iberian Peninsula. Disjunctively the species is found in parts of northern Algeria. Specific countries of distribution include Russia, Ukraine, Belarus, Estonia, Latvia, Lithuania, Moldova, Finland, Sweden, Norway, Denmark (including the Faroe Islands), United Kingdom, Ireland, Netherlands, Belgium, Germany, Austria, Poland, Hungary, Romania, Czechoslovakia, Yugoslavia, Albania, Switzerland, Italy, France, Spain and Portugal.
 | | Close-up of Cirsium palustre flowerheads, Ravalen, Uppland, Sweden. Photographer: Mats Björkqvist | |
MORPHOLOGY
C. Palustre is very spiny and may attain a height of up to two metres. Erect ribbed stems are robust and sturdy, with moderately dense concentrations of spines. The narrow spiky leaves are conspicuously lobed, especially the uppermost; moreover, leaves are near glabrous above, whilst long hairy beneath. Lowest leafs are narrow and elliptical, but uppermost leaves are lanceolate. Basal rosettes in a colony are so high that they may crowd out competing flora. The species is sexually dimorphic. Marsh Thistle is considered biennial; (Halevy) however, flowering in some habitats does not commence until the plant is five to seven years of age, having strengthened its vegetative stem structure. Moreover, flowering may occur after the first year of vegetative growth. The species is not necessarily a strict biennial, and often does not complete its life cycle until the second year once blooming has started.
The discoid flowerheads are one to two centimetres in diameter and appear most commonly from June to early September. Typically a cluster of heads terminate upper stems, with egg-shaped or cylindric involucres being slightly longer than one centimetre. Flower colour exhibits polymorphism, with purple being the most common manifestation; however, white flowering specimens are not uncommon particularly with increasing elevation (Richards) such as in the Swiss Alps. Outer bracts are frequently sticky and exhibit a pointed spine. Buff coloured achenes are adorned with a luminous apical collar. Each plant may produce up to 2000 seeds, and seeds may result from self or cross-pollination. Interestingly the cross-pollinated seeds can travel up to ten times further due to their different pappus design; presumably, this adaptation allows the cross pollinated seeds to colonise areas further from the mother plant. Pollinators, particularly known from butterfly studies, prefer the purple to white flowers for their visits. (Mogford)
ECOLOGY
Throughout Western Europe a common plant association is the Juncus subnodulosus/ Cirsium palustre fen meadow. (Rodwell) Flora constant to this habitat include Filipendula ulmaria, Equisetum palustre, Holcus lanatus, Lotus pedunculatus and Mentha aquatica. This sedge and rush dominated ecosystem achieves a natural canopy height of 60 to 90 centimetres in swampy fen expanses. The J. subnodulosus/C. palustre fen meadow appears to be co-evolutionary with mid Holocene agriculture, since its species content is encouraged by low intensity grazing or sporadic mowing; moreover, the greatest species richness appears correlated with a lack of intensive grazing. Often the unit is a relict of surrounding more intensive agriculture adapted to higher, better drained ground. The importance of this fen meadow habitat is thus appreciated as the sole habitat extant for many wetland wildlife species. In England the most frequent occurrences are in Anglesey, East Anglia and north Buckinghamshire. Juncus inflexus is a common, but not essential, member of the association. Carex disticha and C. actiformis are frequent sedge associates to the habitat. Frequently the J. subnodulosus/C. palustre fen meadow will transition to a tall herb Phragmitetea community which usually incorporates Calamagrostis canescens and Pharlaris arrundinacea. In the lowlands of south England the J.subnodulosus/C. palustre fen meadow is typically a peaty, mineral rich soil regime, although a wide variety of soil types and textures may be found.
A common subcommunity is the Briza media/Trifolium association, which typically includes Juncus inflexus and J. artiulatus. Rumex acetosa and Deschampsia cespitosa. This floristically rich subcommunity often contains a gamut of herbs such as Potentilla erecta, Cardamine pratensis, Trifolium repens, Prunella vulgaris and Dactylorhiza fuchsii. Another interesting subcommunity is the Carex elata association. Here is characteristically an open upper tier, with typical flora including Hydrocotyle vulgaris, Equisetum fluviatile, Epilobium palustre, Potentill palustris and Lythrum salicaria.
The Iris pseudacorus subcommunity is sometimes found within the larger association. My observations in the Baltic countries found this subcommunity to appear in deeper more persistent marsh areas. The Iris pseudocorus association shares a number of the flora species present in the last two subcommunities discussed, but may also include Valeriana officinalis, Lysimachia vulgaris, Thalictrum flavum and less commonly Calystegia sepium and Epilobium hirsutum. Bryophytes are sparsely present and may involve Plagiomnium rostratum, Brachythecium rutabulum and Calliergon cuspidatum.
C. palustre is not shade tolerant, (Lambers) and thus is well adapted to the fen meadow associations discussed above, where it is one of the high tier flora in the habitat. Germination is enhanced after a chilling episode, (Fenner) which effect may explain the ability of the species to thrive in long, cold winter regimes. C. palustre along with its genus member C. arvensis is considered allelopathic; (Ballegaard) however, the flowerheads provide food for a wide range of wildlife (Zietz) including insects and mammals. At least 39 species of insects are known pollinators including Coleoptera, Hymenoptera and Lepidoptera. At least four species of hoverfly, have larvae that feed from C. palustre. (Rotheray) Cheilosia fraterna larvae feed upon mature rosettes and stem elements, although the larvae of Cheilosia proxima attack only the young rosettes. The univoltine larvae of Cheilosia grossa bore into the stems of C. palustre. Cheilosia albipila larvae were less aggressive, but demonstrated stem predation. The seedhead fly, Terellia ruficauda preys upon the Marsh Thistle, and is virtually the only insect being considered as a biological control agent to mitigate North American invasions. (Fraser)
The longhorn beetle Agapanthia villosoviridescens is a polyphagous species known to attack C. palustre as well as most other Cirsium members. Females pierce the stem by gnawing and oviposit in the pith channel, allowing the instar larvae ready access to pith as a food source. Epiblema scutulana larvae prey successively upon achenes, rosettes and stalks of the Marsh Thistle.
A population of C. palustre has been identified that is thought to have been relatively stable since the last major Ice Age (e.g. approximately 10,000 years before present) and studied in Jutland, Denmark. This locale near Hald is believed to have been kept in dynamic equilibrium by constant spring upwelling. Studies here revealed that seedling mortality is very high, whilst mortality at successive life stages of the plant is modest.
CONSERVATION AND HUMAN ASSOCIATION
As discussed above, C. palustre appears to have thrived throughout the Holocene, as Western European agriculture advanced. Seed germination studies may provide a clue to this relative accession to dominance in a period where most wild plant species are in decline. The seedbank of Marsh Thistle is actually stimulated by occasional ploughing, creating an interval of exposure to surface light, when the plant canopy has been thinned and conditions for germination are favourable. This phenomenon explains why C. palustre is commonly found in abundance in marginal areas not regularly cultivated, but which plots are near more upland regularly ploughed and mowed fields. Such damp plots were in clear evidence to me on parts of the island of Saaremaa in Estonia. In North America, however, the Marsh Thistle is not native and is viewed as a noxious weed.
However, the marshy fen meadow habitats so well populated by C. palustre are subject to ongoing degradation by conversion to agricultural uses, as crop failures increase in Asia and Africa and greater production pressure is placed upon European areas where water supply is more reliable; China's grain productivity appears to have peaked about 1995, and, due largely to groundwater overdrafting on the North China Plain, China has become a major importer of cereals. In Africa, not only is desertification and warfare contributing to agricultural decline, but the burgeoning population is placing increasing pressure on other world regions such as Europe to mitigate mass starvation.
REFERENCES
* C. Correns. 1916. Untersuchungen uber Gesclectes bestimmung bei Distelarten, Sber. Preuss. Akad. Wiss., 20, 448-478
* J. S. Rodwell. 1998. British Plant Communities, Cambridge University Press, 640 pages
* Abraham H. Halevy. 1989. Handbook of Flowering, CRC Press, 776 pages, v. 6
* A. J. Richards. 1997. Plant breeding systems, Chapman and Hall, 529 pages
* D. J. Mogford. 1974. Flower colour polymorphism in Cirsium palustre: Pollination, Heredity, 33, 257-263
* Sigurd Håkansson. 2003. Weeds and weed management on arable land: an ecological approach, CABI publishers, Wallingford, United Kingdom 274 pages
* Hans Lambers, Francis Stuart Chapin III, Francis Stuart Chapin and Thijs Leendert Pons. 2008. Plant physiological ecology, Springer Publishers, 640 pages
* Michael Fenner. 2000. Seeds: the ecology of regeneration in plant communities, Page 399 of 410 pages
* T.K. Ballegaard and E. Warneke. 1985. Observations on autotoxic effects of Cirsium palustre from a spring area–Jutland, Denmark, on its seed germination and seedling growth, Holarctic Ecol., 8, 59-62
* H.Zietz. 1954. Neue Beitrage zur Entwicklungsphysiologie von Cuscuta gronovii Wild., Biol. Zentralbl., 73, 129-155
* Graham Rotheray. 1988. Larval morphology and feeding patterns of four Cheilosia species (Diptera: Syrphidae) associated with Cirsium palustre L. Scopoli (Compositae) in Scotland, Journal of Natural History, Volume 22, Number 1, January-February 1988 , pp. 17-25(9) Publisher: Taylor and Francis Ltd
* Nancy Fraser. 2000. Cirsium palustre (Marsh Thistle), Ministry of Forests: Forest Practices Branch, Range Section, Noxious Weeds Program, Kamloops, BC
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