A tuberous perennial herb of dry chalk soils, most frequent in arable fields, especially where cultivation has ceased, and sometimes dominant in arable reverting to pasture. It also grows in rough or broken turf on chalk downs, field edges, in hedgerows and scrub, on roadside verges and in quarries. Reproduction is by seed. Lowland.
There has been little change in the range of this species since the 1962 Atlas. It requires open soil for seedling establishment, but mature plants can thrive in closed swards and the tubers survive shallow-ploughing. Its absence from the North and South Downs is difficult to explain in view of its abundance in similar habitat at Boulogne (France).
Suboceanic Southern-temperate element.
Light (Ellenberg): 7
Moisture (Ellenberg): 4
Reaction (Ellenberg): 9
Nitrogen (Ellenberg): 4
Salt Tolerance (Ellenberg): 0
January Mean Temperature (Celsius): 3.3
July Mean Temperature (Celsius): 16.3
Annual Precipitation (mm): 633
Count of 10km squares in Great Britain: 13
Count of 10km squares in Ireland: 0
Count of 10km squares in the Channel Isles: 0
Atlas Change Index: 0.14
RDB Species Accounts
Bunium bulbocastanum L. (Apiaceae)
Status in Britain: LOWER RISK - Near Threatened.
Status in Europe: Not threatened.
This species is a plant of calcareous soils, and is one of the few which, in Britain, are confined to the chalk (Ratcliffe 1977). It is mainly a plant of arable fields, especially where cultivation has ceased, but is also frequent in rough or disturbed downland and open scrub. Road verges, quarries, tracksides and hedgerows are other habitats. It is very rare in established downland, but even there, past disturbance is often suspected (Dony 1953). Associated species in these communities include Arrhenatherum elatius, Bromopsis erecta, Centaurea nigra, Chaerophyllum temulentum, Crataegus monogyna, Dactylis glomerata, Festuca rubra, Galium mollugo, Heracleum sphondylium, Knautia arvensis and Medicago sativa. On arable land it occurs most frequently with Sinapis alba, and on rough or broken downland with Anthyllis vulneraria (Dony 1953).
B. bulbocastanum is a glabrous perennial up to a metre tall, flowering in June and July at about the same time that the leaves wither. It grows from a globose tuber which is said to be edible (Tutin 1980). The plant requires patches of bare ground into which to seed, and is often abundant in the early seral stages of grassland development. However, once established, it can persist for many years in more mature and closed swards. It is probably intolerant of regular heavy grazing, being favoured in sites where there is only intermittent disturbance.
First described in Britain in 1839, B. bulbocastanum is now known from more than 50 localities, most of which are in Bedfordshire and Hertfordshire. There are a few outliers in neighbouring Cambridgeshire, but in Buckinghamshire (Ivinghoe Hills) it may now occur in just one place. However, despite its apparent local decline, there has been no significant change in its population nationally since the early days of recording. There are some colonies of several thousand plants, but most populations are smaller, some consisting of only a few plants.
In general, it does not appear to be particularly threatened, though individual populations are known to be at risk from residential development and road building, as well as from agricultural intensification. Neglect is also a factor at some sites, leading to dense scrub development. However, suitable habitat is still sufficiently frequent throughout its range such that it is likely to persist, particularly where there is a degree of disturbance.
The range of B. bulbocastanum extends from England southwards to north-west Africa and the Balearic Islands, and eastwards to central Germany and Croatia (Tutin 1980). It is rare in several countries, and legally protected in Germany.
PLANTATT - Attributes of British and Irish plants. (.zip 1455KB) This dataset was compiled and published in 2004, and last updated in November 2008. Download includes an Excel spreadsheet of the attributes, and a PDF explaining the background and nomenclature. Note that the PDF version is the booklet as published, whereas the Excel spreadsheet incorporates subsequent corrections. A hardcopy can be purchased from the Centre for Ecology and Hydrology.