An annual of bare or sparsely vegetated habitats on oolitic limestone, found on screes, stony banks and open pastures; also found in old quarries and on broken rocks. Elsewhere it is usually a casual of waste places, although populations have persisted on railway embankments. Lowland.
T. perfoliatum has declined because of loss of open habitat due to scrub invasion, the lack of grazing or the cessation of quarrying. It has poor seed dispersal, and it has been suggested that many colonies away from the Cotswolds result from seed spread in the slipstream of trains.
Eurosiberian Southern-temperate element; widely naturalised outside its native range.
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Light (Ellenberg): 8
Moisture (Ellenberg): 4
Reaction (Ellenberg): 8
Nitrogen (Ellenberg): 2
Salt Tolerance (Ellenberg): 0
January Mean Temperature (Celsius): 3.3
July Mean Temperature (Celsius): 16
Annual Precipitation (mm): 732
Height (cm): 17
Perennation - primary
Life Form - primary
Clonality - primary
Count of 10km squares in Great Britain: 9
Count of 10km squares in Ireland: 0
Count of 10km squares in the Channel Isles: 0
Atlas Change Index: -0.94
Plantatt Conservation Status
RDB Species Accounts
Thlaspi perfoliatum L. (Brassicaceae)
Status in Britain: VULNERABLE. WCA Schedule 8.
Status in Europe: Not threatened.
Of all the species associated with limestone, T. perfoliatum is one of the rarest. It is a plant of bare, open, broken limestone in natural habitats, and in artificial sites such as quarries and railway banks. The only species with which it can be said to grow regularly is Erophila verna, but other associates are Anthyllis vulneraria, Centaurea nigra, Cerastium glomeratum, Hippocrepis comosa, Lotus corniculatus, Myosotis arvensis, Pilosella officinarum and Thymus polytrichus.
This species is an annual. It is variable in size, but often no more than 3 cm high when the first flowers open, which may be as early as late March (Rich 1991). At this time the inflorescence is more or less sessile in the leaf rosette and individual plants easily overlooked, but plants subsequently become taller and much more noticeable. Since it has no special means of seed dispersal its ability to spread is limited, and once established, must rely on continual disturbance of the soil to keep down competitors and to maintain an open habitat. The longevity of seed in the soil, and the size of seed-banks are not known (Baskin & Baskin 1979).
T. perfoliatum has been recorded from a total of 35 hectads in Britain, and considered to be native in nine of them. Within these hectads, a recent evaluation has found that it has probably been recorded in about 45 native and 37 introduced sites. Since 1986, T. perfoliatum has been recorded in only nine native (seven in Gloucestershire and two in Oxfordshire) and three introduced sites. It was extant in all nine native sites in 1996 (Rich, Lambrick, Kitchen & Kitchen, in press). Populations can vary greatly in size according to climatic and habitat conditions; a particular site may, for instance, hold a few tens of plants and many thousands in successive years. National totals in 1992, 1994, 1996 and 1997 were about 10,000, 4300, 71,000 and 8700. Most of the large increase in 1996 was accounted for by 50,000 plants at a site not counted in 1994 and 1995. However, every site showed an increase in 1996, this being attributed to the long summer drought of 1995 which reduced competitors and created open ground for germination (Rich, Alder, et al. 1996). There are few records of T. perfoliatum away from its main area, and these are generally of non-persistent colonies in ruderal habitats. However, colonies on railway banks in Somerset and Rutland have persisted for more than twenty years (Rich, Kitchen & Kitchen 1989).
Losses in the past have been due to habitat destruction and degradation, including agricultural improvement, herbicides, ploughing, grubbing up of hedges, and invasion of scrub. The maintenance of open communities with areas of dry, open, broken soil is essential for the survival of T. perfoliatum. In some sites, grazing by domestic livestock or rabbits achieves this, but in the absence of grazing, other conservation management is essential. At some sites, it is necessary to disturb the ground more or less annually to remove potential competitors and provide suitable conditions for germination. Some populations are under threat because of the lack of appropriate management.
It occurs widely in southern Europe, becoming less common as it reaches its northern limits in Belgium and central Germany. There are scattered populations further north in southern Sweden and on the Baltic coast. It also occurs in North Africa and the Near East, and as an introduction in North America.
A. J. Showler
Atlas text references
1986. Atlas of north European vascular plants north of the Tropic of Cancer. 3 vols.
Jalas & Suominen (1996)
1965. Vergleichende Chorologie der zentraleuropäischen Flora. Volume 1. 2 vols.
Lambrick et al (1998)
1999. British Red Data Books. 1. Vascular plants, edn 3.