A Grass For Every Month In North Craven

Judith Allinson

JOURNAL
2009

North Craven
Heritage Trust

The development of man is crucially linked with the evolution of grasses that have large seeds; these grew in the fertile triangle of the Middle East, China and what is now known as South America and were a vital constituent of his diet. It can be said that the whole of mammal evolution and human civilization depends on grasses. They continue to be vitally important, world-wide in man’s diet. These large seeded grasses are not indigenous to Britain but the greenness of North Craven is due to the 72 native grasses which grow here. Woodland is the natural vegetation for this county, but cattle, sheep and rabbits, introduced by humans, have changed our landscape to grassland.

The aim of this article is to give you a start in identifying some of these 72 native species and help you with a few obvious ones. For each month a particular grass is chosen. To help us understand something about the abundance of individual species in our area we can refer to the book ‘Plant Atlas of Mid-West Yorkshire’ by Phyl Abbott (2005). It shows maps of the distribution of plants species in this part of Yorkshire including North Craven.

There are several questions to be asked. What actually is a grass? What is the importance of grasses? What is the tallest grass in Craven? How many grasses are there in Craven and how many in the UK? Can certain grass species be used as indicators - can they tell you things about the soil, the rarity of the vegetation type, what animals you may expect to find?

The Latin name for the family of plants known as grasses is Poaceae (previously Graminae). This is the fourth most diverse plant family with 10,000 species in the world, after daisies, peas and orchids. Grasses include reeds, bamboos, maize and rice and not one of them is poisonous. Humans get three quarters of their calories from cereals - rice, sorghum, millet, maize, wheat, barley and oats. 300 years ago drovers brought their cattle down to the sweet moist pastures above Malham and they lived mostly off oat porridge. Three species provide almost two thirds of our calories; maize, wheat and rice. Cereals are not grown in the Dales now. Most crops need a minimum temperature of 6慢 and from October to April it is often below this. There are 72 native species of Poaceae growing wild in North Craven plus about 7 non-native. The Kew website says: ‘Of some 620 genera and 10,000 species of grasses found world-wide, only 54 genera and 150 to 200 species are truly native to Britain.’ There are 39 native genera plus 3 genera for non-native species in North Craven.

The recognition of grasses can seem overwhelming at first. There is a rhyme which may help with the most basic fact of how to tell a grass from other grass-like plants: “Sedges have edges and rushes are round and grasses have joints which go down to the ground.” Sedges have solid triangular stems - hence the edges. Rushes have round stems sometimes filled with pith. Grasses have hollow stems that are solid and swollen at the nodes - think of a bamboo cane - (yes, bamboo is a type of grass). Nodes are the places along the stem where the leaves arise. The grass stem often bends at the nodes so the nodes can be referred to as joints.

January

The only grass to flower all year round is Annual Meadow-grass (Poa annua). Annual plants get through their life cycle in one year. They are easily uprooted and may grow between paving stones. All Poas or Meadow-grasses have their flowers arranged on a branched structure called a panicle - and the panicles look like a spreading Christmas tree, though rather a diminished one in the case of Poa annua. In Poas, the emerging leaves are folded lengthways and have boat shaped tips. But all you have to remember is that if you find a small grass in flower in mid-winter it is likely to be Annual Meadow-grass.

February

In 2009 one grass stood out above the snow at the fen at Malham Tarn - the Common Reed (Phragmites australis) silhouetted against the winter sun. With its 2m tall stems, its now straw-coloured dead brush-like heads, and its dead brown leaves blown to one side, it is easily recognisable. The Reed is extremely rare in North Craven, (apart from one or two places where it has been planted in reed beds for septic tanks). In general reeds are grass-like plants growing in wet places. Some reeds are grasses, some reeds are not grasses.

Reeds that are grasses include: Common Reed - about 5 sites in North Craven; Reed Canary-grass (Phalaris arundinacea) which is common along river banks in Craven; the very rare Narrow Small-reed (Calamagrostis stricta), at one place at Malham Tarn, and the uncommon Wood Small-reed (Calamagrostis epigejos), about 5 places, some in limestone pavement. The club-headed rods in the pool at Helwith Bridge Moss are not grasses - they are Reed-mace (Typha latifolia) sometimes also, but wrongly, called Bulrush.

The Common Reed and the very similar Reed Canary-grass are easily recognisable, because the sheaths articulate and when it is windy the sheaths move round the stem so that all the blades point in the same direction. Both tall grasses have blades up to and over 1cm wide, growing in patches in damp places, both spreading with rhizomes (underground shoots). The Reed now grows in less than a handful of places in North Craven. The places where it would once have grown such as the glacial lakes in the flat-bottomed Ribble and Wharfe valleys have now been drained. I was told that the monks of Fountains Abbey would harvest reeds for thatching from the Wharfe near Kilnsey.

But there is a conundrum. Thirty years ago at Malham Tarn we were proud of the Reed growing in a former trout pool at Malham Tarn Fen, at 1200 ft above sea level near its altitudinal limit for so far north. In the last twelve years it has suddenly started spreading out to the surrounding parts of the fen where other rare plants grow, shading them out. It presents a management problem. Its thick rhizomes easily spear through the surrounding peat so it can travel several metres a year. Is the increase in Common Reed due to climate change?

What is the tallest wild grass in Craven? The Reed. But cultivated maize sometimes grown near Hellifield is a rival. Planted bamboos are much taller, such as the India Fountain-bamboo (Yushania anceps) planted by Reginald Farrer at Clapham.

March

My favourite grass is Blue Moor-grass. For grass to grow the temperature has to be at least 6蚓. In Craven this is not achieved in March. However one special grass is starting to put its bluey-purple head out and that is Blue Moor-grass (Sesleria caerulea). Any grass in flower in March or early April growing in limestone pavement on our limestone cliffs must be Blue Moor-grass, a Craven speciality. It does not grow in the south of England so botanists come all the way up here from London to see this special plant. Until recently, it had not been found south of Yorkshire, but now a site has been found for it in Derbyshire. It seems to grow in areas once covered by glaciers.

If you split open a Blue Moor-grass shoot in November or December you will find the baby flower inside - it is the only grass in the UK to do that. The limestone places where Sesleria grows can become very dry in summer as water sinks through the cracks in the limestone. The plant puts resources into getting the plant to flower and fruit early before there is a drought. If you would like to recognise Sesleria before it is in flower go to limestone cliffs, e.g. Winskill Stones or Gordale Scar, and look for a tufted grass that has leaves about 6mm wide and that are folded as they emerge and have slightly boat-shaped tips. There are whitish persistent sheaths at the base of the shoot. The blades curve like a scythe - sometimes upwards, sometimes downwards, and often bluish .

One other small grass-like plant which you might look out for in March, though it more normally flowers in April, is Good Friday Grass, also called Field Woodrush (Luzula campestris). It has brown flowers and long white hairs on the leaves. It grows in lawns and old meadows. Woodrushes belong to the Rush family. It is necessary to know the differences in fruit structure to distinguish grasses, sedges and rushes. This information can be found in Collins ‘Grasses, Sedges, Rushes and Ferns of Britain and Northern Europe’ by Fitter, Fitter and Farrer (reprinted 1984); the illustrations are by Annie Farrer.

April

In parts of the country that have no Blue Moor-grass, the first grass to appear is Sweet Vernal-grass (Anthoxanthum odoratum). Sweet because it smells nice, and vernal because it grows early in spring. It is the only common grass to have a smell, and it is this grass that gives the smell to hay. It is the roots that give it the smell, rather than the leaves or flowers. It smells of coumarin, coconut or creosote according to your nasal sensitivity. This grass grows in old-fashioned hay meadows and is characteristic of several vegetation communities that Natural England deem important. However Anthoxanthum can also often be found scattered in many other habitats: in woods, road verges, even as a weed in gardens.

Did you know that grasses and herbivores evolved at the same time? Grasses have a structure which allows them to grow again easily when eaten. All their buds are at the base of the plant. If the leaves get eaten, more buds grow from the base. Grass leaves consist of a sheath and a blade. The growing part of a blade is at its base - so if the blade tip gets eaten, the base of the blade continues growing. Contrast this with a young tree - most of its buds are on its branches - if the branches are eaten the buds are lost.

Mammals seemed to have started evolving about the same time as grasses. Grasses contain silica bodies (phytoliths) in their cells. Animals eating grasses wear down their teeth grinding up the grass leaves. Some of the first mammals had teeth for grinding. People once thought that grasses evolved long after the dinosaurs. But recently some fossil dinosaur droppings have been found containing phytoliths - so grasses were beginning to evolve at the end of the Dinosaur era.

May and June

Two large silvery grasses, which sparkle in the sun and have large flowers and long distinctive awns (bristles), can be used as indicators of old hay meadows. Downy Oat-grass (Helictotrichon pubescens) is very similar to Meadow Oat-grass (Helictotrichon pratense) which comes out a month later. These are two of the Indicator Species of Old Grassland used by the YDNP and English Nature in their survey of the National Park. The other two are Quaking Grass (Briza media), and Marsh Fox-tail (Alopecurus geniculatus).

Tom Lord who farms at Winskill, Langcliffe, says he gets three crops from his meadows: the first crop is sheep in April. The second crop is the hay or silage - from mid May to July he keeps the stock out and the flowers and grasses grow. In earlier days it would take quite a long time to cut the hay and bad weather might interrupt proceedings, so some years it would be quite late when the hay was cut - even October. Now with modern machinery and big bale silage it is possible to cut the crop earlier. After cutting, the field is left for a week and then cattle are put in. This third crop of grass is called the ‘fog’. His land is on limestone and if it is a dry summer, grass growth is limited far more by lack of water than by lack of nutrients.

July

North Craven has distinctive moorland and bogs. A heathery bog in May is white with Cotton-grass (a type of sedge - Eriophorum vaginatum). By July it is covered with a shiny, shimmering of Wavy Hair-grass, (Deschampsia flexuosa). Both have needle-like leaves. If the biomass of all the land designated as Heather moorland in England was cut and weighed, there would be more Wavy Hair-grass than Heather. Wavy Hair-grass grows in acid woodland such as at the top of Ingleton Glens, and in conifer plantations..

August

Common Bent (Agrostis capillaris) is a small delicate inconspicuous grass but it is one of the commonest grasses. Remember running barefoot on the garden lawn as a child? You were probably running on Common Bent, along with needle-leaved Red Fescue. It grows in nutrient-poor lawns, slightly acid grassland pastures, sandy soils and heather moorland.

At the edge of a lawn taller shoots of Common Bent escape the lawn-mower. It has an inflorescence like a spreading Christmas tree with many hundreds of tiny spikelets - tiny because each spikelet contains only one flower. Bents (Agrostis) have only one flower per spikelet, Meadow grasses (Poas) have several flowers per spikelet.

Common Bent becomes much more exciting on metal ore spoil heaps such as at Pikedaw above Malham. Here it is about the only grass present. The word Bentham (Benetain in the Domesday book) comes from the word meaning rough grass or reeds. So I like to think it could refer to Common Bent. However other grasses were once called bent - including Purple Moor-grass (Molinia caerulea) once known as White Bent which grows in abundance in white sheets on damp parts of Newby Moor and the moor south of Bentham.

September

Some grasses have recently appeared in Britain from abroad, and some grasses not normally found in Craven have spread in from other parts of Britain, especially along road verges. These can increase, and give interest to a botanist’s species list. I have seen the Hungarian Brome (Bromopsis inermis) for a long time, growing in the verge opposite what was Stainforth Youth Hostel where the Settle-Carlisle line passes underneath. This is a tall plant (1m) with a panicle of long narrow spikelets. The base of its shoots are crimson and it has black rhizomes. It has been used as a fodder crop in the past.

Another is Reflexed Saltmarsh-grass (Puccinellia distans), which now grows a couple of hundred metres south of the Brome, by the road. It has come in with the salt. I first noticed this in North Craven about 15 years ago on the edge of the A65 on Newby Moor at the summit just west of the Little Chef. Since then it has been appearing in more places along salted roads, such as the northern junction of the A65 Settle Bypass.

Silky-bent (Apera spica-venti) is the rarest of these introductions. I noticed it for the first time in 2008 close to the Saltmarsh-grass. It was with the white crucifer seaside plant Spring Scurvy-grass that normally grows on the pavement that is kept free of long vegetation because the pavements are sprayed by the Council each year. This is smaller than Common Bent and each spikelet has a 2mm long awn (bristle). It is classified as a nationally scarce arable weed. It is native in the south of England and east Yorkshire. It is only the second record for our area. The other record is a plant found on Ingleborough, brought in with material when the Three Peaks footpath was being built, and recorded as the highest known site for this plant.

Another beautiful grass to look out for is Foxtail Barley (Hordeum jubatum), naturalised from North America which is conspicuous on the A65 at the north junction of the Settle bypass (seen in August rather than September).

October

There are still grasses in flower - even as late as October and False Oat-grass (Arrhenatherum elatius) can flower from May to December. It has big spikelets with two flowers per spikelet and one long awn per spikelet. It grows well where there is no grazing so can be found on road verges, along the Settle-Carlisle railway and at the edge of woods. If grazing is removed from a field of neutral grassland for several years, False Oat grass starts to come in. Some sites can be swamped by this species because the landowners no longer graze cattle. Here in Craven however if the same grass is found growing on ledges on limestone cliffs it can grow with a rich assemblage of species including rare fen species.

November

Tufted Hair grass (Deschampsia cespitosa) grows well when grazing is removed from a field with deeper soil. It can swamp out smaller species.

December

In December, Purple Moor-grass (Molinia caerulea) can be seen as big dead tufts on wet areas of moorland. It is Britain’s only deciduous grass. In late autumn the nutrients go down to the buds at the base of the shoot. The leaves die and fall to the ground or blow away. I have heard farmers call it ‘Blow away grass’. Once the leaves have blown away the tuft of shoot bases can look and feel like a hedgehog.

Some areas of Purple Moor-grass contain very few species - perhaps some Bog-moss (Sphagnum) and Tormentil (Potentilla erecta). This vegetation type is very tussocky and difficult to walk across. In other areas, where Purple Moor-grass grows at much lower density, there is base rich water springing up and there can be a variety of much rarer plants. Here one often finds Quaking-grass (Briza media) and even in December one can find the dead Quaking-grass heads.

Editors' note

This article celebrates Judith Allinson’s thirty years of running annual Grass Identification courses at Malham Tarn Field Centre. There are four original water-colours by Annie Farrer on display here, sold to the Centre by the painter at a generous price. When Judith runs courses she shows students these paintings of Sweet Cicily, Hogweed, Burnet Saxifrage and Angelica. The Journal cover shows a Meadow Cranesbill (Geranium pratense) painted by Annie Farrer.

The illustrations can be seen in colour on the website www.NorthCravenHeritage.org.uk