IRISH PLANT MONITORING SCHEME – IDENTIFYING GRASSES

This pdf guide introduces you to the most common grasses you will encounter when surveying grassland plots as part of the Irish Plant Monitoring Scheme.

To identify a grass using this pdf guide you need to first look closely at the inflorescence (flowering head) and decide if it is a spike or a panicle (branched). In some grasses the inflorescence will be one-sided. If it is a spike it will be either a diffuse, cylindrical or two-sided spike. If it is a panicle you will need to look closely at the structure of the spikelets which make up the inflorescence.

For full details on identifying grasses in Ireland you should consult this guide which was published by the Data Centre in 2015. The structure of this pdf guide is similar to the structure used in that publication.

Your grass inflorescence will either be a spike or a panicle, and is made up of spikelets. In some grasses it will be one-sided.

Spikelet structure

When the inflorescence is a panicle you will need to look closely at the spikelets. The most important things to check for are:

Is it a one-flowered or multi- flowered spikelet?

Is the glume longer or shorter than the lemma? Inflorescence one-sided

It can be a one-sided panicle or a one-sided spike. In these grasses all spikelets occur on one side. You should rotate the inflorescence fully to determine if it is one-sided or not

Cock’s-foot - Dactylis glomerata

 Very common & distinctive grass  Dense clusters of green or purple-tinged spikelets in a one-sided panicle  Hairless  Flat leaves with rough edges

Mat-grass - Nardus stricta

 Occurs on peat soils  Stiff rod-shaped one-sided inflorescence  Very slender purple-blackish spikelets, 1- flowered  Narrow bristle-like leaves

Crested Dog’s-tail Cynosurus cristatus

 Flattened dense spike  Spikelets in groups of 2 or 3 on one side  Short narrow leaves, glossy below

Inflorescence a diffuse spike

Sweet Vernal Grass Anthoxanthum odoratum

 Loosely tufted grass  Spikelet 3-flowered, lower 2 sterile  Short, flat, pointed leaves  Sweet scented when crushed or dried

* This pdf guide includes only the most common species you are likely to see within each subdivision Inflorescence a cylindrical spike

Phleum: Inflorescence stiff. Glumes with an awn, lemma awnless.

Alopecurus: Inflorescence soft/silky. Glumes awnless, lemma with a long awn.

Timothy - Phleum pratense  Inflorescence 6-15cm or longer  Leaves 2-4(10)mm wide and up to 45cm long (lower leaves)

Marsh Foxtail - Alopecurus geniculatus  Inflorescence up to 7cm long  Long blunt ligule, 2-5mm long  Stems often bending upwards at the nodes. Often has creeping stolons.

Meadow Foxtail- Alopecurus pratensis  Inflorescence up to 13cm long.  Very short, flat-tipped ligule, 1-2.5mm long.  Upright stems. Stolons absent.

Inflorescence a two-sided spike

Perennial Rye-grass Lolium perenne

 Very common grass  Leaves & sheaths hairless  Sheath base wine-red in colour

Inflorescence a panicle – one fertile floret per spikelet

Velvet Bent - Agrostis canina sens. lat.  Panicle ovate in shape  Lemma with an awn  Leaves narrow  Spreads by obvious creeping stolons

Common Bent - Agrostis capillaris  Panicle diffuse and pyramidal in shape  Lemma with no awn  Leaves flat  Spreads by rhizomes, sometimes stolons

Creeping Bent - Agrostis stolonifera  Panicles dense and linear in shape  Lemma with no awn or very short  Leaves flat  Spreads by obvious creeping stolons

* This pdf guide includes only the most common species you are likely to see within each subdivision Inflorescence a panicle – more than one fertile floret per spikelet & glume longer than lowest lemma

Heath-grass – Danthonia decumbens  Narrow, compact panicle with 3-6 green or purplish spikelets  Flower heads don’t usually open & are rock hard  Lemma awnless  Leaves hairy

Crested Hair-grass – Koeleria macrantha  Tufted, downy grass  Short-stalked, 2-3 flowered, purplish or greenish-white spikelets  Glumes with silvery margins  Lemma awnless  Leaves can be bristle-like

Yorkshire-fog – Holcus lanatus  Spikelets numerous, 2-flowered  Glumes hairy  Upper lemma with a very short delicate awn  Stems and leaves with a velvety feel, fine soft hairs.  Sheaths purple striped at base (‘striped pyjamas’)

Tufted Hair-grass – Deschampsia cespitosa  Forms large tussocks  Panicles loose and nodding, up to 50cm long  Awns not clearly visible  Leaves flat (2-5mm wide) and prominently ribbed and rough on upper side

Downy Oat-grass – Avenula pubescens  Tufted grass  Spikelets 2-3 flowered  Long silky hairs emerge from spikelet  Lemma with long, dark brown, bent awn (>10mm) arising from the back  Basal leaves flat and downy

* This pdf guide includes only the most common species you are likely to see within each subdivision Inflorescence a panicle – more than one fertile floret per spikelet & glume shorter than lowest lemma

Quaking-grass – Briza media  Distinctive grass  Graceful branched panicle with short- oval spikelets on slender stalks  Spikelets many-flowered, green or purplish

Purple Moor-grass – Molinia caerulea  Forms dense tussocks in wet peaty habitats  Panicle long and branched, with numerous mostly purple spikelets  Leaves flat & hairless, sometimes sparsely covered with long hairs

Floating Sweet-grass – Glyceria fluitans  Aquatic  Spikelets flattened 18-35mm long, 6-14 flowered  Stems flattened  Leaves hairless

False Oat-grass – Arrhenatherum elatius  *Glume is just shorter than the lowest lemma  Spikelets 2-flowered  Leaves broad and flat (4-10mm wide)  Lower lemmas with long awns (>10mm), usually bent  Usually hairless grass but can be variable  Stems can be hairy at the nodes

* This pdf guide includes only the most common species you are likely to see within each subdivision Inflorescence a panicle – more than one fertile floret per spikelet & glume shorter than lowest lemma

Poa has flattened spikelets, no awns and hairless leaves with boat-shaped tips that cannot be flattened without splitting. Annual Meadow-grass - Poa annua  Ligule short and pointed, 1-4mm long  Leaves often transversely wrinkled  Generally a smaller plant

Rough Meadow-grass - Poa trivialis  Ligule long and pointed, up to 7mm long on flowering stems  Leaves taper like a long isosceles triangle

Smooth Meadow-grass - Poa pratensis sens. lat.  Ligule short and blunt, 1-3mm long  Leaves parallel-sided (do not taper to point until the very tip), tend to be slightly blue-green in colour

Festuca has branched, spreading panicles. Spikelets are held rigidly. Leaves hairless, often bristle-like.

Red Fescue agg. - Festuca rubra agg.  Very variable widespread grass  Spikelets reddish-green  Lemma with short awn (<3mm)  Lower leaves bristle like, upper leaves flat

Sheep’s Fescue agg. - Festuca ovina agg.  Occurs in heaths, mountainous areas  Spikelets reddish-green  Lemma with short awn (<1.5mm)  All leaves bristle-like, most leaves on plant <10cm long  Strongly tufted

Schedonorus has branched, spreading panicles. Spikelets are held rigidly. Leaves hairless. Like Festuca but larger and more robust and has distinct auricles.

Tall Fescue - Schedonorus arundinaceus  Lemma sometimes with short awn or absent  Small auricles fringed with minute hairs  Leaves dull green, rough on underside, especially at the edges

Meadow Fescue - Schedonorus pratensis  Lemma without an awn  Auricles small, fine pointed, not hairy  Leaves bright green, glossy and smooth beneath

* This pdf guide includes only the most common species you are likely to see within each subdivision