A collection of wildlife photographs

Friday, 27 June 2014

Grass identification in Epping Forest

On the 7th and 8th June, the Field Studies council led a grass, sedges and rushes identification course in Epping forest, on the outskirts of London, next to the M25. It was an informative couple of days, and we documented some specimens to enable future reference to their characteristics. Grasses have economic importance in the production of grain, are often abundant in habitats, and can be used as habitat indicators. Thus, learning how to identify them is worthwhile.

Wavy Hair-grass, Deschampsia flexuosa
Wavy Hair-grass is indicative of acid grassland. It grows to between 20 and 45cm tall, and has long pointed ligules (ligules are membranous, or sometimes hairy, barriers between the leaf blade and the stem, which prevent water running into the leaf sheath and causing them to rot). The leaves are very thin and wiry, as shown in the photograph below, which helps distinguish it from Tufted hair grass, Deschampsia cespitosa. 
Wiry leaf blade of Wavy Hair-grass, Deschampsia flexuosa 

Tufted Hair-grass, Deschampsia cespitosa 
Tufted Hair-grass is found on more neutral soils than Wavy Hair-grass and can also grow taller, to between 20 and 120cm. Despite both plant species having long pointed ligules, these two Hair-grass species can be told apart by their leaves. Tufted hair grass has wider leaf blades (2-5mm) than the needle-like leaves of Wavy Hair-grass.
Flower head of Tufted Hair-grass, Deschampsia cespitosa
Long, pointed ligule of Tufted Hair-grass, Deschampsia cespitosa.
Note the wider leaf blade than Wavy Hair-grass
Sheep's Fescue, Festuca ovina
Sheep's Fescue is found on both calcareous and acid soils. The spikelets (small, subunits of a grass flower) of Fescue species, are distinctive, in that they are long, slender and pointed. One of the most reliable ways to tell Sheep's Fescue from Red Fescue, is that Sheep's Fescue plants are not linked by below-ground rhizomes or above-ground runners. 
Flower head of Sheep's Fescue, Festuca ovina

False Oat-grass, Arrhenatherum elatius 
False Oat-grass is indicative of neutral grassland, and is widespread, flowering in June and July. The spikelets are 7-10mm long, and one conspicuous, bent awn (stiff, bristle-like projection from a spikelet), of 10-20mm length, protrudes from the lower lemma. The lemma are a pair of scales that enclose the floret, yet another pair of scales, called the palea, are located within the lemma, also enclosing the floret. The upper lemma of False Oat-grass does not typically have an awn, and so there is generally just one awn, on False Oat-grass spikelets, as shown in the photograph below. False Oat-grass can grow tall, between 50-150cm in height at reproductive maturity. Each spikelet contains just 2 florets (small, individual parts of a flower).

 Spikelets of False Oat-grass, Arrhenatherum elatius
Meadow Foxtail, Alopecurus pratensis 
Meadow Foxtail is also indicative of neutral grassland. It appreciates ancient grasslands, or rich, moist soil. It has a dense flower head, so that spikelets are very close together, and this flower head typically tapers slightly to its tip. The photograph below shows that at the correct developmental stage, the plant is covered in red-brown 'anthers', which contain the pollen essential to pollinate the stigmas of a plant, before seeds can be produced. As shown in the lower picture, its ligules are short and truncate, between 1-2mm in length.
Flower head of Meadow Foxtail, Alopecurus pratensis
Short, truncate ligule of Meadow Foxtail, Alopecurus pratensis

Yorkshire Fog, Holcus lanatus 
Yorkshire Fog is typically found on neutral and improved grassland. Yorkshire Fog is easy to identify both in and out of flower. Its vegetative structures are covered in dense white hairs, depicted in the photograph to the right, and thus its stems and leaves feel furry to the touch. Other indicators of neutral grassland include Cock's foot, Dactylis glomerata and Crested dog's tail, Cynosurus cristatus.

Hairy stem and leaves of Yorkshire fog, Holcus lanatus

Perennial Rye-grass, Lolium perenne 
Perennial Rye-grass is indicative of improved, or amenity grassland. Improved grassland has been altered in terms of its species composition from unimproved grassland, by the application of fertilisers or herbicides or even high densities of grazing. Amenity grassland is regularly mown to be used as a park or football field. Perennial Rye-grass is easy to identify when in flower, because the spikelets are alternately positioned up the stem. Couch Grass, Elymus repens also has alternately arranged spikelets. However, the spikelets of Perennial Rye-grass are positioned with their narrowest side to the rachis of the flower head, and the spikelets of Couch Grass, as shown in the picture below, can be distinguished from Perennial Rye-grass by being fixed by their broadest side onto the rachis.
Perennial Rye-grass, Lolium perenne
Couch GrassElymus repens assessed from couch

Red Fescue, Festuca rubra 
Red Fescue is also indicative of improved grassland. As mentioned earlier, its confusion with Sheep's Fescue, can be avoided by looking to see if plant individuals are joined by stolons or rhizomes. Red Fescue has below-ground rhizomes or above-ground runners between plants, whereas Sheep's Fescue plants are not linked. 

Barren Brome, Bromus sterilis
Barren Brome is common in disturbed sites, such as by footpaths. It has a distinctive loose and drooping flower head, with V-shaped spikelets, that are 40-60mm in length. The leaf blades and sheaths are both hairy. However, the stems are hairless, so can be separated from Yorkshire Fog, which has entirely hairy leaves and stems.
Loose and drooping flower head of Barren Brome, Bromus sterilis 
Wall Barley, Hordeum murinum
Wall Barley is another species abundant in disturbed sites, such as on waysides or next to buildings. All True Barleys have spikelets arranged in two clusters of three, one on each side of the flower head. The flower head is covered in tough spikey awns, different to Meadow Barley, Hordeum secalinum and Sea Barley, Hordeum marinum, which have soft awns, but similarly to rare alien, Mediterranean Barley, Hordeum leporinum. Wall Barley can also be distinguished from other native forms of True Barleys, because its glumes (the pair of scales that enclose the entire spikelet - not just the floret as the lemma and palea do) have hairy edges towards their base.
Flower head of Wall Barley, Hordeum murinum

Timothy, Phleum pratense
Timothy, also known as Cat's tail, is often found in field margins, prone to disturbance in the form of trampling. Timothy has a cylindrical flower head, to 15cm in length. The photograph below shows that the spikelets are densely packed into the flower head. Its leaves are hairless, and both the stem and leaves are smooth to the touch. The ligules of Timothy are blunt, to 6mm in length. Additionally, the lowest three internodes (sections of stem between nodes) are short, and bulbous.
Dense flower head of Timothy, Phleum pratense
Blunt ligules of Timothy, Phleum pratense

Creeping Soft-grass, Holcus mollis 
Creeping Soft-grass is often found in disturbed habitats, as well as in meadows, and is in the same genus as Yorkshire Fog. Instead of being completely downy like Yorkshire Fog, it has 'hairy knees', in that its nodes (the pronounced points on the stem where a leaf is attached) are hairy, as shown in the photograph below. Its ligules are reasonably blunt, but longer than those of Yorkshire fog.
The 'hairy knees' of Creeping Soft-grass, Holcus mollis
Soft Brome, Bromus hordeaceus
Soft Brome is the most common form of Brome in UK. Frequently found on waste ground, meadows and arable fields, Soft Brome grows to 10-100cm. It has compact, oval spikelets, characteristic to Brome species, which in this species are typically covered in soft bristles. Unlike the drooping flower head of Barren Brome, its flower head is erect, yet still nods slightly in the wind. Soft Brome flowers between June-August.

Flower Head of Soft Brome, Bromus hordeaceus
Rough Meadow-grass, Poa trivialis 
Rough Meadow-grass is another species that can be identified through touch. When the plant is flowering, its leaf sheaths become very coarse, as its name suggests. Additionally, its spikelets are oval shaped, characteristic of all Meadow-grass species. The ligules of Rough Meadow-grass are long (between 4-10mm) pointed and membranous, as shown in the lower of the two photographs. Rough Meadow-grass is another plant which can propagate vegetatively, through over-ground stolons (i.e. runners). It is common on meadows and pastures or cultivated land.
The oval spikelets of Rough Meadow-grass, Poa trivialis
Long, pointed ligule of Rough Meadow-Grass, Poa trivialis
Grass species can be difficult to identify, but whilst in flower at this time of the year, identification is readily achievable. Although there is a conception that grasses all look the same, it is important to take away from this, that there are morphological differences between species which enable them to be clearly distinguished from each other. They are so abundant in most habitats, that getting your eye in to them, unlocks a whole new world at our feet.

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