Grass and Grassland

The need for maximum self-sufficiency in terms of home-grown feeding-stuffs has placed greater and greater emphasis on the production of more and better grass and upon its more efficient utilisation by grazing and conservation. A greater cattle population has thus been maintained at a higher level of output of both milk and beef, and there has been a marked revival in the sheep industry.

CHAPTER 3 (#ulink_13de4614-1cf9-50d2-b0c5-5dcae21d4a93) THE GRASS PLANT AND ITS VALUE TO MAN

In this chapter I shall begin with a brief description of the various parts of a grass plant, emphasising the features that are of importance to agriculture. A fuller and more detailed account may be found in Dr. Hubbard’s excellent Penguin volume Grasses (1954).

To the non-botanist all grasses look very much like one another at first sight. On closer inspection, however, differences in habit and form of growth and particularly of inflorescence are very apparent. There are grasses which are Lilliputian in size, contrasting violently with the largest members of the family, the bamboos, bearing great masses of blooms on spikes or panicles a foot or more long. Grasses, too, display an immense capacity for adapting themselves to their environment, some making their home in water or along the banks of streams and rivers, while others survive the scorching heat of the desert and or the intense cold of the polar regions. Some grasses are annual and complete their life cycle in one year, such as the very common annual meadow grass (Poa annua). Others like the soft brome grass (Bromus mollis) are biennial, the seed germinating in late summer or autumn and the plant flowering and seeding the following year. Finally, there are vast numbers of perennials, like perennial ryegrass (Lolium perenne) and couch grass (Agropyron repens), which are potentially immortal, producing new shoots or new lengths of rhizomes for ever if conditions allow. A bamboo may survive for thirty or forty years or even longer. Unlike the annuals and biennials, which bear flower-heads on all or most of the shoots, in the perennials the flowering shoots are accompanied by vegetative shoots, the number of which depends upon the duration of the grass.

These vegetative and flowering shoots are not different in origin. Both shoots start off as a vegetative structure—a very short-jointed stem bearing two ranks of leaves, one leaf at each of its closely-spaced joints or nodes and arranged alternately along the stem, which is constantly producing new leaves at its tip; thus there is a continuous sequence of growth. As each leaf reaches full size the older ones die away, to be replaced by fresh leaves. Meanwhile the stem remains extremely short, but branching often takes place. Buds in the axils of the leaves grow out to form a new short-stemmed leafy shoot, and these in turn produce further shoots in the axils of their leaves, so that a dense tuft is quickly built up. This process of increase in the number of shoots, without any marked lengthening of the stem, is particularly noticeable in young cereal plants during the first few months of growth, and has been given the special name of “tillering,” each shoot being referred to as a “tiller.” Obviously tillering capacity in the cereals means that less seed per acre needs to be sown than would be the case were only a single shoot formed from each seed. If each tiller produced an ear to be harvested flowering would be spread over a long period, hence ripening would be very uneven and farming operations complicated; but the normal wheat-field is sown thickly so that only one or two of the earliest-formed tillers on each plant are able to flower, which ensures that all the ears of grain are ready for cutting at the same time. Pastures, on the other hand, produce more stock food since the grasses cover the ground more rapidly to form a sward or turf, and recover from mechanical damage comparatively quickly because of this characteristic.

A turf of vegetative shoots may be a foot or more in height, but it consists almost entirely of leaf. The stems are still extremely short and completely hidden, so that in a typically tufted grass at this stage of growth all the stems and buds are within about half an inch of the ground. It is only in exceptionally tall-growing grasses, such as the bamboos, that long, upright vegetative stems are produced at an early stage. In the case of creeping grasses there may be some elongated stems but these are horizontally directed and spread along or through the ground as stolons or rhizomes. By way of contrast, the lower internodes of some grasses may become swollen with plant food, and these grasses are known as “bulbous.”

This characteristic of the grasses—the growth-buds remaining close to the ground—determines their value as food for grazing animals. If an upright-growing plant, like kale or a young tree seedling, is grazed off to within an inch or two of the ground it will have lost the greater part of its stem, together with its apical bud and most of its axillary buds. It may recover by the development of new shoots from the base of the stem, but it is unlikely to survive many such grazings. In marked contrast to this a vegetative grass plant grazed

in this way suffers very much less damage. It is clear that unless the grazing is exceptionally close as a result of many animal mouths to the acre or continuous stocking, only the leaves will be removed and all the stems and buds will be left intact and able to continue their growth with comparatively little check. Grasses can therefore withstand repeated grazing and treading by stock. In the face of such grazing, grasses obviously have a great advantage over other taller-growing plants; indeed, except where drought or extreme exposure prevents the growth of taller plants, grassland exists mainly because of grazing. If there were no grazing animals there would be, in a climate like that of Britain, very little grassland, only scrub and forest.

Grass shoots do not, however, remain indefinitely in this vegetative stage; eventually they change to the flowering condition. When this occurs the stem apex ceases to produce new leaves and instead forms a rudimentary inflorescence. Once this change has taken place in a shoot, it produces no more new leaves and no more axillary shoots or tillers; the inflorescence develops, the stem elongates to bring it up above the level of the leaves, the flowers are pollinated, the fruit ripens and is shed, and the whole shoot dies. Growth of the plant is then continued by other tillers which are still in the vegetative state. The change from the vegetative stage to the flowering stage is usually a response to length of day; most British grasses are “long day plants” and so these changes take place in them as the days lengthen from spring to early summer.

The tiller must, however, have reached a certain size before it can respond to the increasing hours of daylight and this size varies in different grasses. If a small tiller can respond, then all the tillers will reach the necessary size during the year, before the days become too short again. In this case therefore all tillers will flower and die. Thus there will be no vegetative tillers left to continue growth and the plant behaves as an annual. If, however, the tiller cannot respond until it has reached a larger size, it will not flower until the late summer (aftermath flowering) or it may not flower that year. If, as is true of some grasses, a period of low temperature is necessary before response can take place, flowering will be delayed until the following spring. Meantime, the tiller, while still in the vegetative condition, will have produced further tillers so that the plant behaves as a long-lived perennial. Such plants produce some flowering shoots each year but always remain sufficiently vegetative to ensure continued growth.

With few exceptions grasses have fibrous roots—in some species they are tough and cord-like—which arise adventitiously from the lowermost node or nodes of the stem. This capacity of grasses to produce numerous fibrous roots is of prime importance for it means that grasses, unlike plants with a main tap root, have great powers of recovery after injury. When the main tap root of such a plant is injured the plant probably dies; root injuries to grasses on the other hand may even stimulate new growth. Thus severe harrowing of an old pasture with heavy spiked harrows, which cut into the turf, tears out much of the matted growth, increases aeration, and brings about rejuvenation, with the result that the pasture “freshens up” with new growth. Similarly the groundsman, using “pruning” machines on the sports turf or lawn, encourages new, strong root and leaf development.

The roots of different species vary in length and are equipped with a very great number of root hairs. In some cases, like couch grass, underground, scaly, whitish or brownish creeping stems or rhizomes are formed and both roots and scale leaves are produced from the nodes of these rhizomes. In other cases, like creeping bent (Agrostis stolonifera) and rough-stalked meadow-grass (Poa trivialis), thin, greenish or purplish, surface-creeping stems or stolons, like strawberry runners, are formed from the nodes, from which fibrous roots and green leaves are produced. Thus rhizomes and stolons are really modified stems, and grasses with such rooting, mat-forming systems cover the ground very rapidly in consequence. Such a characteristic is not always desirable and in some cases it presents serious problems. Any bud-bearing portion of a rhizome which is broken off from the root system can start a new and independent plant. Thus couch grass which can be a very serious weed on some types of arable land, becomes a menace by the very speed with which it reproduces itself. The small pieces of rhizome broken and dispersed in the course of cultivation give rise to new colonies of plants and it is not unknown for the growth of couch to be so great that the intended crop is smothered. Moreover, the diversion of food materials to the formation of such non-photosynthetic and inedible structures as stolons and rhizomes has the effect of reducing the maximum yield, and such grasses as bent and couch are, therefore, most unproductive. The highest yielding agricultural grasses, such as the ryegrasses, cocksfoot and timothy, are tufted, non-creeping species.

The flowering stems (“culms”) of the grasses are usually cylindrical and hollow except at the nodes or joints, where the stem is firm and solid and from where the leaves emanate. Culms vary not only in size, rigidity and number of nodes but may grow erect, prostrate or arise from a curved or prostrate base. The stems are usually smooth and highly polished. The leaves are parallel-veined and arranged in two rows alternating one with another on the stem. Each leaf is composed of a lower portion known as the “sheath” which may form a cylindrical tube enclosing the stem, or may be split, with the margins overlapping one another. Near the ground, the sheath may be coloured red, purple or brown which is constant for each species and constitutes an aid to identification. In some species, only the veins are coloured. The upper portion of each leaf is called the “blade”; this may be flat, rolled up and bristle-like, or folded about the mid-rib with the upper surface inwards, while the blades may be erect, drooping, or at right angles to the sheath. The blade, usually long and narrow with parallel sides or tapering to a pointed or blunt tip, often widens out at its base to form either a ledge or ear-like projections or teeth called “auricles,” which clasp the stem. Where the blade joins the sheath there is usually a membranous outgrowth, called the “ligule,” which may be pointed, blunt or ragged, long or short, or may be represented by a line of hairs. These characteristics afford still further means of identification. The leaves of some grasses are hairy, others free from hairs (glabrous); if present, the hairs may be most abundant on the sheath, on the upper or lower surfaces of the leaf blade or, in some instances, confined to the ribs or margins.

This key to the identification of the commoner pasture grasses by means of their vegetative characters has been compiled to enable the enthusiast when walking over a farm to distinguish the chief species making up the swards. It has been made as simple as possible and deals with only a few of the better known grasses. Readers who wish to identify a much wider range of species should consult Hubbard’s Grasses (1954).

KEY FOR IDENTIFICATION OF COMMON GRASSES WHEN NOT IN FLOWER

The inflorescence varies widely in the different genera and, if present, is the easiest means of identification. It is made up of a varying number of “partial” inflorescences called spikelets, each of which is composed of one or more flowers, each with two enveloping protective structures, the lemma and the palea. In most cases the grass flowers bear both stamens and pistil but in maize (Zea mays), for instance, the male flower is produced in the “tassel” and the female on the “cob” with its greatly thickened axis. Very rarely male and female flowers may be borne on different plants, as in buffalo grass (Buchloe dactyloides). The form of inflorescence is determined according to the way spikelets are arranged on the stem. The spikelets may be borne directly on the main axis to form a spike as in the ryegrass or couch grass; they may be borne on simple branches to give a raceme, as in false brome (Brachypodium spp.), or, as in the majority of grasses, borne on secondary, tertiary or even more sub-divided branches to give a panicle. The length and stoutness of the branches provide a wide variety of panicles between the extremes of an erect, close inflorescence, superficially resembling a spike, as in foxtail (Alopecurus spp.) or timothy, and one which is long and drooping, loose and spreading, like the bromes.

Flowering usually takes place from May to July, although in mild winters a number of species develop flower-heads in December or even January. Annual meadow grass, on the other hand, can generally be seen in bloom throughout the year. The first grass to flower in the spring is holy grass (Hierochloë odorata), which is in bloom about the end of March, but this species is very rare in the British Isles, and is confined to three Scottish counties and one Irish. Meadow foxtail (Alopecurus pratensis) and sweet vernal grass may flower in April, the ryegrasses in May, cocksfoot and the fescues in June, and timothy in July. Woodland and mountain species are somewhat later in flowering than species of the same genera growing in more open habitats or at lower altitudes. The early-flowering grasses are usually those in which only a comparatively short day is required for flower initiation; the later are those needing a longer day.

Since the actual flowers of grasses are very simple and show comparatively little variation, classification and identification have to depend largely on the structure and arrangement of the spikelets. Each true flower consists only of a single pistil with (usually) two styles, and (usually) three stamens, plus, in most grasses, a pair of minute scales which are known as “lodicules” and which have been regarded as representing very reduced sepals. Each flower is protected by two much larger structures, the inner, usually two-keeled, palea and the round, single-keeled, lemma. The lemma and palea fit closely together over the flower and are only separated for a short time when the lodicules swell up temporarily, pressing them apart, and allowing the styles and stamens to protrude and wind-pollination to take place.

Each true flower plus its lemma and palea is known as a “floret” and the spikelet consists of from one to about twenty florets. At its base there are two (occasionally one or none) protective structures, the glumes. Both the lemmas and the glumes may be furnished with bristles (awns), which are useful features for identification.

The following key will enable the more important species to be identified in the flowering stage.

KEY FOR IDENTIFICATION OF COMMON GRASSES WHEN IN FLOWER

Grasses show an amazing tolerance to external conditions. For instance sheep’s fescue, which grows down to sea level in this country, has also been recorded on the highest mountains in Britain and at nearly 18,000 ft. in the Himalayas. Then again, many grasses from low-lying habitats in temperate regions adapt themselves to high altitudes in tropical countries. Others survive wide differences of climate, the classic example of adaptability being perhaps sweet vernal grass, which flourishes from sea level to above the snow line, is equally at home on sand, loam or clay, and is found in many countries of the world with vastly different climates, ranging from North Africa to Siberia.

A number of other grasses are on the other hand very specialised in their habitats. Moor mat grass is usually associated with the margins of peat moors, not because it will not grow elsewhere, but because it grows better under such conditions than any other. A number of grasses can endure strong salt water, such as marram grass (Ammophila arenaria), the salt marsh grasses (Puccinellia spp.), and sea lyme grass (Elymus arenarius), and these are confined to our coasts. Marram and sea lyme are used for stabilising wind-blown sand, while the salt marsh grasses and rice grass (Spartina townsendii) are mudbinding plants of salt marshes.

Other grasses adapt themselves well to a high water content in the soil, and “water meadows,” where periodic and controlled flooding was carried out, were in use until quite recent times. To a limited extent this is still practised in Wiltshire and Dorset. The operative phrase is “controlled flooding” for good drainage of the soil is imperative for the growth of the best types of grasses useful to the farmer. Under waterlogged conditions the deficiency of an adequate air supply to the plant roots spells failure for the ryegrasses, cocksfoot, timothy, rough stalked meadow grass, and similar productive species. Under such conditions tussock grass (Deschampsia caespitosa), rushes (Juncus spp.) and sedges (Carex spp.), which are inedible for livestock, become dominant.

The true seed of grasses is not normally seen, since the fruit-coat is very thin and firmly attached to the single seed. This type of fruit is known as a caryopsis: a wheat grain is a good example. Most grass “seeds” consist of a single grain tightly enclosed within the lemma and palea; attached to the base is generally a small portion of the axis of the spikelet. In the case of Yorkshire fog, meadow foxtail, and a number of other grasses the “seed” is, however, an entire spikelet and consists of the two glumes, and the lemma, palea and grain of one or more flowers, while in the case of the brown “seed” of timothy and most wheats the grain is shed free from its lemma and palea. The bulk of timothy seed, however, is the silver grey “seed” composed of the caryopsis complete with lemma and palea. These examples illustrate how the grass “seed”—that part of the plant which is actually sown either naturally or in agricultural practice—differs from the true seed.

Grasses are distributed in the main by the wind, for the caryopses with their enclosing glumes are light and capable of being carried long distances. Some seeds are plumed, others possess tufts of hairs which doubtless increase their buoyancy. Gales and whirlwinds are likely to exert a great influence in conveying seeds from one place to another. In Lincolnshire, for instance, a whirlwind has been known to tear up a tuft of couch grass by the roots and carry it for over twenty miles, and it has been suggested that since gale force winds are common during the period July to September, when many grasses are seeding, they must be a very important means of dispersal and probably of greater influence than normal wind-drift.

One must not overlook the influence of water in carrying grass seeds long distances. Their buoyancy in the air is equalled in many cases by their facility in floating on water, while the upper peduncles act as sails to assist them in their passage across estuaries and round coasts. In addition too, it is not unknown for whole plants to be transported by the sea and it is recorded that the sugar cane on Cocos Keeling Island was derived from a clump from Java, seven hundred miles away. Bamboos have also been known to be moved from place to place. Drifting rhizomes in rivers and in the sea also bring about dispersal and in Europe, Puccinellia maritima, Elymus arenarius and Ammophila arenaria are known to be dispersed by these means. Tufts of annual meadow grass are often carried long distances by rivers and indeed, of all grasses this is perhaps the most determined to establish itself by some means or another. At Seale Hayne it is regularly removed from the roof gutters and spoutings thirty feet above ground level. It springs up between cobblestones and flags in the heart of our largest industrial cities and I have found it growing in birds’ nests in late autumn after the nests have been abandoned and are well soaked with rain. This is particularly the case in thrushes’ nests which are mud-lined. It has also been found 12,000 feet up in the Himalayas where it was concluded that man or his yak must have been the means of conveyance. The glumes of some grasses bear stiff reflexed spines which help the seeds to cling to clothing, to the wool or fur of animals, or to the feathers of birds. In the Belgian Congo termites store large quantities of a species of Cynodon in their nests and when these are abandoned the grass is established. I heard of a most interesting case when in New Zealand, where man quite unwittingly was the means of introducing red-top. Emigrants before leaving Nova Scotia filled their mattresses with hay which included red-top. They travelled to the Cape of Good Hope, thence to Australia, and finally settled in New Zealand where the mattresses were abandoned; the grass seeds germinated and thus an American grass became established in a strange country!

The farmer classifies a grass as useful or useless according to its particular value to him. There are over a hundred and fifty different species of British grasses but of these no more than twenty are of real agricultural value and indeed, on the majority of farms, considerably fewer are regarded as of consequence.

The value of grass to the farmer depends upon (a) productivity, or yield, (b) feeding value or chemical composition, (c) palatability, (d) persistency, (e) winter greenness and (f) earliness. To the groundsman, however, it is obvious that such factors as (a) slowness of growth, and (b) wearing capacity and ability to recover from harsh treatment, are of much more importance, while the landscape gardener must also look for very different qualities in grasses to form ornamental lawns or for foliage work in border and greenhouse. Quite naturally, in the case of both groundsman and gardener, the species used are often different from those used in agriculture, and in these pages I have concentrated on the latter.

The yield of herbage produced by any grass, which is the farmer’s first consideration in making a selection, depends upon its tillering capacity, the facility with which it recovers from cutting or grazing, and the duration of growth each season. An excellent illustration is obtained by comparing perennial ryegrass and bent grass. The former tillers freely and grows steadily from early spring until late in the autumn and indeed, in the mild wet south-west of England it grows all the year round. In contrast to this, bent grass grows for a short period only and yields comparatively little bulk, and in consequence is discarded by the farmer as being of no value. To him it is in fact a weed.

Then the ability of a grass to recover from cutting or grazing is also of great importance, defoliation being more favourable to the development of young tillers in some species than in others. Recent work has tended to stress the importance of the influence of intensity of defoliation on the yielding capacity of grasses. It appears that by leaving some growth—say one to two inches—when cutting or grazing a sward, more rapid recovery of growth follows, and hence more bulk or weight of grass over the whole season is obtained, than when animals are allowed to graze tightly to the ground or the mowing machine blades are set as closely as possible to the bare earth. The full answer is not yet known, for species vary in this respect and are also subject to seasonal variations.

While most grasses are palatable if eaten in the early stages of growth, quite a number develop harsh or hairy leaves, or even spines on the leaf margins, as they grow older, and hence are rejected by stock. A grass which may be highly valuable in all other respects can be rendered useless by this factor; Yorkshire fog and the coarser forms of tall fescue are typical examples. In practice it is not always possible to utilise a field at the ideal stage of growth, when the grass is most palatable to stock, and thus grasses which retain their palatability over a long period are particularly valuable. Yield and feeding value are complementary factors, the one without the other being useless to the farmer. In this connection the structure of the grass is important, for species with a high proportion of leaf to stem are much more valuable than stemmy ones, since the leaves are more palatable and contain more protein than the stalks. Grasses become coarse and stemmy with a corresponding reduction in feeding value as they reach the seeding stage. Plant breeders of recent years have endeavoured, therefore, to produce strains of grasses with a high proportion of leaf to stem and with a natural reluctance to produce flowering heads.

From the farming angle as well as the ornamental, a capacity to remain green during the winter months is important. This extends the grazing season and reduces the need for expensive artificial feeding of livestock. Certain varieties of meadow foxtail and red fescue, for instance, have been bred to produce leafage during February and March.

In the last thirty years a great deal of attention has been paid to variations of type within each grass species. Perennial ryegrass, for example, may be tufted, stemmy and short-lived or it may be leafy and persistent. Some types are very prostrate in growth whilst others are erect. Some are very palatable, others less so. The same comments are applicable to all the important species of commercial value such as cocksfoot, timothy, and meadow fescue, and these are classified into what are technically known as “cultivars” (but more familiarly as varieties or strains), and multiplication by division and seed of these strains is carried out on a large scale.

It is very evident there can be no simple answer to the question, “Which is the best grass?” Quite apart from the great variations which we have seen exist within the grasses themselves, the complexity of the problem is magnified by varying systems of management whether for grazing or conservation, by the use of different seeds mixtures, by fertiliser and herbicidal treatment, by disease and insect pest, and by the varying requirements of sheep and cattle. The whole fascinating study is unfolded in the following chapters.

CHAPTER 4 (#ulink_f1f89a5d-3a1e-50cd-b0b3-6e832840a61c) TYPES OF BRITISH GRASSLAND

Centuries of biotic influence have brought about the formation of our so-called natural types of grassland, for even the wild stretches of hill and moorland, which to most people epitomise natural grassland, owe their existence to the influence of countless generations of grazing animals, particularly sheep. Without man’s influence heather, bracken, and scrubby growth soon colonise the land to act as the forerunners of bush, pine and rowan until a dense forest growth occupies the countryside. Let us, therefore, be precise and speak of uncultivated and cultivated grassland. The former group includes moors, downs, wolds, heaths and fens, broadly termed rough grazings, while the latter includes the rich permanent pastures and meadows which are “cultivated” by regular mechanical treatment with harrows and rollers and receive periodic applications of the essential plant nutrients though the turf is left undisturbed. Included in this group is the ley or short duration grassland which is ploughed periodically. The subdivisions are clearly seen in table 4:

TABLE 4. SUBDIVISIONS OF GRASSLAND

The transition from ley to permanent pasture or meadows, thence to rough grazing and scrub, and finally to forest, is an orderly, gradual process, the different phases being clearly recognisable yet merging one with another. The great areas of rough grazings are known to all countrymen and townsmen alike and a brief outline of the different types of grassland in this group will give added interest to the countryside.

The soil of our moorland areas, including those of Scotland and the Lake District, the Pennines, the Yorkshire moors of the north-east, the Welsh mountains, and the moors of Cornwall, Devon and Somerset, is acid or “sour” and a marked lime shortage is invariably associated with a deficiency in phosphate and potash. Under such conditions our useful grasses and clovers cannot survive and the flora is very restricted and specialised, the degree of acidity, the rainfall and the drainage determining the specific type of herbage found in any particular stretch of moor. Free-draining land is often in close proximity to bog, but in the majority of cases the sterile condition of the soil has resulted in an accumulation of undecomposed vegetation, “mat,” near the surface and the grassland is said to be “matted.”

On the wetter soils the dominant species is often flying bent (Molinia), the long straws of which were once used by country people for making stiff carpet brushes. Should the peat be waterlogged then cotton grass, deer grass, heath or square-stemmed rush will be found in varying amounts. If the peat is well drained, as on hill sides and knolls, the soil still being very acid, then the dominant grass is matgrass, so named because it grows in dense matted tufts, the hard bristle-like wiry leaves being much too tough for cattle or sheep to eat. Often associated with matgrass will be sheep’s fescue, bilberry and heather. On really deep soil, which is fundamentally good land, bracken is frequently dominant, and when this land is cultivated it yields excellent crops of potatoes and oats. So runs the old adage, “Copper under Heather, Silver under Gorse, Gold under Bracken,” which proved so true in the wartime ploughing-up campaign of 1939–45. Heather land yielded poor crops, even with generous fertiliser treatment, for the soil was too hungry and lacked body, whereas surprisingly good crops followed the ploughing in of bracken. Gorse land gave results somewhere between the heather and the bracken.

Heather moor is primarily sheep country and normally carries about one ewe to four or five acres. Hardy cattle, such as the Galloway, may sometimes be seen in association with sheep on the best moors. The periodic burning of the heather prevents the development of scrub and encourages new growth and, in late winter especially, young heather shoots are valuable in providing adequate sustenance for the sheep. When the burning is too slow, i.e. the fire does not sweep rapidly over the heather and the roots are damaged in consequence, bilberry frequently replaces the heather which represents the next phase in the succession.

The most valuable of the moorland or hill pastures contain sheep’s fescue, red fescue and bent as the dominant species and although these grasses are at the bottom of the nutritional scale as we shall see, they have the advantage of demanding the minimum of attention from the farmer in order to keep a stable sward. Bracken is generally the most serious intruder but this can be kept in check with regular attention. On the moors of Cornwall and Devon rough uncultivated pastures contain Agrostis setacea