This is one of my favourite grasses. It is among the first grasses I learned to identify and one of the easiest. Its flowers are arranged in an exquisite delicate panicle and they dance and shimmer in the softest breeze. But its leaves are armed with tiny teeth on the upper surface; they can saw into human skin.
One distinguished grass authority said this was ‘A coarse worthless grass of wet and badly-drained soils..’ (Hubbard 1968). Worthless? No-one would use such a word these days – but he was referring to its value as food for cattle. He may have been wrong (see below).
It is a tall grass (50-200 cm), forming tussocks of many connected individuals (‘tillers’ is what the individual units are called). Tussock-forming grasses like this make new tillers every year, each one capable of producing a flower and often withering once its job is done. The tussock can become very large, and many grasses form large tussocks which can be very old, perhaps 100 years in some species.
Panicles of Deschampsia cespitosa. Photo: John Grace
In well-grown plants there are 1000-2000 spikelets, each bounded by two purplish bracts (‘glumes’); there are two flowers within each one. Anthers emerge on the early morning. They are also purplish but the stigmatic surface (like a miniature bottle brush) is pure white. Pollen is dislodged in even the slightest breeze and in a dense sward like the one shown below the pollen grains are captured by the stigma of another plant (cross pollination is the norm).
Flowers of D. cespitosa, showing anthers and ‘bottle-brush’ stigma. Photo: John Grace
The leaves have sharp spines on the upper surface giving the leaf a very rough feel when rubbed from tip to base. This is a very useful character for identification. Another good character is the ligule. It is exceptionally large (4-8 mm), and jagged at the edges.
Ligule of D. cespitosa. Photo: John Grace
This is a common native plant, widespread in rough grassland, marshes, meadows, woodland and moorland; often on badly drained soils, waysides and ditches. It is not in the ‘top ten’ most frequent of grasses but sometimes it becomes locally dominant. Last year I came upon such a site, in the Pentland Hills near Edinburgh. I went back in the last few days to have a closer look. The site has large areas of this species, alternating with another well-known grass, Yorkshire Fog (Holcus lanatus). The Hills were designated as a Regional Park in 1984, and managed as upland pasture for sheep and recreation (walking, mountain-biking). I knew the site very well before that time but I am sure there was never so much D. cespitosa. The increase may be attributed to the reduction in grazing. Vegetation does change when the grazing regime is altered, but it happens over decades. I remembered a set of articles on this topic from work at Moor House, in the Pennines of northern England.
View of Pentland Hills, showing large areas of a field dominated by D. cespitosa. Photo: John Grace
At Moor House, the site was a rather species-rich and much-grazed grassland. Rawes (1981) reported that D. cespitosa initially occupied just 3 % of the cover. But after 24 years of being fenced to keep out sheep it changed markedly – large clumps of vegetation formed and D. cespitosa increased to 23 %. Rather similar results have been found in the Welsh hills.
This result is however somewhat perplexing, as the leaves of D. cespitosa are well-armed to repel any would-be grazers. In the words of one author ‘The reason cattle avoid it becomes clear on looking at the transverse section of the leaf; it is sharply ridged and each ridge is crowned by a knife-edge of fibres’ (Arber 1934). Despite these defences, tussocks are eaten by horses and may be closely cropped by rabbits (Davy 1980). In a very old paper Hansteen (1896) considered D. cespitosa to be good fodder grass in Norway. I suspect sheep and other grazers eat just the young leaves in the spring. What are the sheep eating at present?. Definitely not these huge tussocks which I struggle to cut with a pen-knife. I should try following one of them with binoculars.
Leaf blade, upper surface, showing ridges topped with tiny spines. Magnification x3. Photo: John Grace
Several grass species have been shown to tolerate soils contaminated with toxic metals (including lead, zinc and copper). Much research on this topic was carried out by Janis Antonovics, Anthony Bradshaw and students at Liverpool University. In one project they examined grasses growing under electricity pylons. These structures are coated with zinc, which slowly washes off and ends up in the soil. Populations from under pylons were tested for zinc tolerance against ‘control’ plants dug up away from the pylons. All five grass species (Agrostis capillaris, Agrostis stolonifera, Anthoxanthum odoratum, Deschampsia cespitosa and Festuca ovina) showed a strong tolerance to zinc, but the most tolerant of all was Deschampsia cespitosa. This work sparked interest in how such rapid evolution could possibly occur over the relatively short period during which the pylons had been standing (about 30 years), and why would one species evolve tolerance more rapidly than others.
Over 90,000 of these pylons (left) carry high voltage electricity across Britain. They are made of steel and coated with zinc. The rain slowly washes zinc into the soil below creating a zone where plant growth is visibly inhibited (right). Some species have developed resistance to zinc toxicity.
Several forms of Deschampsia cespitosa have been recorded. Stace (2019) recognised three subspecies: alpina, cespitosa, parviflora. The most common is ssp. cespitosa, whilst parviflora is found in woods of lowland Britain and alpina is found in mountains. The key in Stace (2019) should enable the subspecies to be distinguished as long as the plant is flowering.
D. cespitosa sometimes produces new plants by vivipary (the germination of seeds in situ without a resting period). This is common in the alpine subspecies, presumably as an adaption to a short season of growth as in many alpine species generally.
Chromosome counts in D. cespitosa ssp. cespitosa show that some indiviuals have 2n = 26, others have between 31 and 44 (more or less triploid) and some are tetraploid (52). This is a perplexing situation but not without precedent in the plant kingdom.
The general ecological attributes of the species are summarised by Grime et al (1988). The plant occurs on a wide range of soils (pH from 4 to 8), shaded or unshaded, with a preference for permanent pastures rather than arable land, limestone rather than acidic substrates, and often occurs on wasteland. Its altitudinal range is 0 – 1130 metres above sea level. In short, it is quite a generalist.
The species is found in all parts of the British Isles. Globally, it is found in all cool-temperate locations: in the northern hemisphere it is widespread and there are scattered records in the southern hemisphere. Its distribution suggests it is limited by the 20 degree June isotherm (Davy 1980).
Global distribution of Deschampsia cespitosa, from GBIF.
As for its name: the genus Deschampsia is named after the French physician/naturalist Louis Auguste Deschamps (1765–1842). The spelling of the species name can be either ‘cespitosa’ or ‘caespitosa’. The meaning of this word is ‘growing in dense tufts, forming mats’.
As for uses: (i) there are many decorative varieties which are available commercially for ornamental use (ii) used for thatching in former times, see http://apps.kew.org/herbcat/getImage.do?imageBarcode=K000674147
References
Arber A (1934) The Gramineae. Cambridge University Press.
Davy AJ (1980) Biological flora of the British Isles: Deschampsia caespitosa. Journal of Ecology, 68, 1075-1096.
Grime JP, Hodgson JG and Hunt R (1988) Comparative Plant Ecology. Unwin Hyman.
Hansteen, B (1896) Studien uiber Weiden und Wiesen in den norwegischen Hochgebirgen. Sonderabdruck aus dem Biologischen Centralblatt, 16, 81-84. (cited by Davy 1980).
Hubbard CE (1968) Grasses. Second Edition. Penguin Books.
Rawes M (1981) Further Results of Excluding Sheep from High-Level Grasslands in the North Pennines Journal of Ecology, 69, 651-669.
Stace CA (2019) New Flora of the British Isles, 4th Edition. C&A Floristics.
©John Grace
Botany in Scotland 