An annual of thin, drought-prone soils on sea-cliffs, growing around rock outcrops, on sunny banks by tracks and footpaths, and in open areas amongst scrub. In Devon, it occurs in similar habitats inland. The outlying sites in Hampshire and Kent are associated with sand- and gravel-workings. It often grows with L. subbiflorus. Lowland.
Recent surveys have shown that L. angustissimus is more widespread in Devon and Cornwall than was previously thought. However, many colonies are small and at risk from scrub encroachment. The persistent seed bank may enable it to respond to a resumption of grazing or disturbance.
European Southern-temperate element.
Light (Ellenberg): 8
Moisture (Ellenberg): 3
Reaction (Ellenberg): 4
Nitrogen (Ellenberg): 3
Salt Tolerance (Ellenberg): 0
January Mean Temperature (Celsius): 5.7
July Mean Temperature (Celsius): 16.2
Annual Precipitation (mm): 952
Count of 10km squares in Great Britain: 55
Count of 10km squares in Ireland: 0
Count of 10km squares in the Channel Isles: 12
Atlas Change Index: -0.23
RDB Species Accounts
Lotus angustissimus L. (Fabaceae)
Slender bird's-foot trefoil
Status in Britain: LOWER RISK - Nationally Scarce.
Status in Europe: Not threatened.
L. angustissimus typically occurs in grassland amongst cliff-top scrub, around rocky outcrops and on grassy banks by the sea. It is a plant mainly of short open-textured and rather 'scruffy' swards over thin drought-prone soils on sheltered slopes of a southerly or south-westerly aspect. At many of its localities cliff-slopes are now covered by dense scrub, and then it is usually confined to narrow pathside banks and verges, and old trackways. Common associates include Agrostis capillaris, Crepis capillaris, Dactylis glomerata, Hypochaeris radicata, Ornithopus perpusillus, Plantago coronopus, Rumex acetosella, Sedum anglicum and Vulpia bromoides, with patches of Ulex europaeus, Rubus fruticosus and Pteridium aquilinum rarely far away. It is often found with its nationally scarce congener L. subbiflorus; indeed, the two species may be "so interwoven ... that they cannot be separated without tearing them to pieces" (Marquand 1901). Johns (1982) observed on Alderney that "if L. subbiflorus isn't around you haven't much chance of finding L. angustissimus", and this is a useful rule of thumb when searching for it in mainland Britain too.
L. angustissimus is an annual, usually germinating in autumn (August - October) and spring (April - May) and flowering between June and October. Observations suggest that autumn-germinating plants flower in June and July, whereas those germinating in spring do not flower until August. Exceptionally, in a wet summer seed produced in June can germinate almost immediately, producing plants which, weather permitting, flower and set seed in early winter. Patches of bare soil are essential for seed germination, and scrub cutting, trampling, fire and especially drought may all be of benefit for this reason (Leach, et al. 1994). Whilst summer droughts help to keep the sward open, they may also cause spring-germinating plants to shrivel and die before they have a chance to flower. It is notoriously erratic in its appearance: one year there may be thousands of plants, whilst in the next it can be almost impossible to find. The reasons for such dramatic fluctuations are usually obscure, although timing and severity of droughts may be important, the largest numbers of plants often occurring in the two summers following a bad drought year. As with L. subbiflorus, it has a persistent bank of buried seed, enabling it to appear intermittently whenever conditions are suitable.
Most L. angustissimus populations are small, and recent surveys indicate that at some sites, particularly in West Cornwall, it may have been lost altogether. Undoubtedly it has declined as a result of scrub encroachment following the demise of traditional management practices such as grazing and burning, and a few populations may have gone owing to agricultural improvement of cliff-top grasslands. Its erratic appearance makes it difficult to assess current status, but it has been seen in 50-60 localities in Britain since 1980, mainly in Devon and East Cornwall but with a few outliers in Hampshire and Kent. The main populations are confined to three areas: Pentire Point, (200-300 plants in 1994), between Polruan and Penlee Point, (more than 600 plants, 1994), and between Prawle Point and Start Point, (more than 6,500 plants in thirteen localities in 1993/94) (Leach 1995). The last, a relatively short stretch of coastline, is currently the plant's main stronghold in Britain. There are several inland sites in South Devon, in the Teign valley and near Bishopsteignton and Dawlish. Its few extant localities in Hampshire and Kent are mostly inland, associated with sand and gravel workings. There are old records from Sussex and Caernarvonshire, unsubstantiated records from the Isle of Wight (Bevis, et al. 1978), and an erroneous report from Dorset (Good 1984).
Some of its largest populations are well protected, occurring within SSSIs and on coastlines owned by the National Trust. However, even on these sites there is a risk that L. angustissimus will continue to suffer through lack of management. Much will depend on prompt action being taken to prevent sites becoming rank and overgrown and, in particular, to limit the spread of scrub.
L. angustissimus is an oceanic-southern species. It is widely distributed in southern Europe, extending throughout the Mediterranean region, and northwards to Britain and all the larger Channel Islands, and eastwards to the Ukraine. It is found on the Azores, in northern Africa and in parts of western Asia. Generally associated with dry lowland grasslands, in parts of southern Europe it is also found in damp grassland on mountains.
S. J. Leach
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.