Bents
What are they?
The bents are an abundant and very important group of grasses, both in natural/semi-natural habitats and in highly human-influenced landscapes. Most species typically have rather slender leaves and very open, graceful flower spikes with very small florets arranged at the ends of long, slender branchlets.
Where are they found?
Bents and similar species occupy a wide range of habitats and can be particularly abundant on acidic soils and in wetlands. They are also widely used as lawn and turf grasses due to their fine leaves, which produce surfaces suitable for high quality 'show lawns' and bowling greens. Soil acidity and whether the soil tends to be dry or wet can often be helpful in species determination, but the distribution of some of the Agrostis species is poorly known due to difficulties in telling these very similar species apart.
Identification
Click here for help with some of the terminology used on the grass pages. The bents can be a difficult group to identify to species and plants in full flower are often the most useful for this purpose. Features to check include the presence or absence of an awn in the flowers and whether the flower spikes remain broadly open or close up after the flowers are finished. Check also whether plants form tufted clumps or have creeping vegetative growths. It can be further useful to determine whether the creeping growths consist of stems (stolons) or roots (rhizomes).
Creeping Bent Agrostis stolonifera
A native perennial and one of the most abundant grasses in the region. Occurs as a native in all types of damp habitats and on heavier soils and is widely used as a tough, turf grass in amenity areas. Flowers July to August. Plants to 80cm in height and forming dense, creeping mats by way of leafy stolons that root from the nodes. Leaf blades 0.5-5mm wide, hairless, finely pointed at the tip, rolled when young but eventually flat. Leaf sheaths rounded, smooth. Leaf ligule 1-6mm in length, membranous, medium to long. Flower spike very narrow when young, open and spreading at anthesis then closing again at fruiting. Spikelets tiny, 2-3mm, clustered towards the tips of very fine branchlets with a single floret in each spikelet. Lemmas not awned.
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Black Bent Agrostis gigantea
A native perennial, widespread on arable field margins and occasionally on allotments and other disturbed areas. Flowers June to August. Plants 40-120cm in height, tufted and producing long, creeping rhizomes. Leaf blades 2-8mm wide, hairless, finely pointed at the tip, rolled when young but eventually flat. Leaf sheaths rounded, smooth or rough. Leaf ligule membranous, 1.5-12mm in length, relatively long. Flower spike narrow when young but soon open and spreading at anthesis. Spikelets tiny, 2-3mm, clustered towards the tips of very fine branchlets with a single floret in each spikelet. Lemmas not awned.
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Common Bent Agrostis capillaris
A native perennial found in most grassy places but especially on acid soils. Widely used as a grass for fine lawns, due to its very narrow leaves. Flowers June to August. Plants 10-70cm in height and spreading by short rhizomes to form slightly tufted patches. Leaf blades 1-5mm wide, hairless, finely pointed at the tip. Leaf sheaths rounded, smooth. Leaf ligule membranous, 0.5-2mm in length, short compared with those of Creeping Bent. Flower spike very narrow when young, open and spreading at anthesis and remaining open at fruiting. Spikelets tiny, 2-3.5mm, clustered towards the tips of very fine branchlets with a single floret in each spikelet. Lemmas not awned. Spikelets may be green (especially in shade) but are more often purplish.
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Velvet Bent Agrostis canina
A native perennial typically found in damp places on acidic soils and most frequent in the east of our region. Flowers June to August. Plants 10-60cm in height and spreading by stolons which root at the nodes to form tufted patches. Leaf blades 1-3mm wide, hairless, finely pointed at the tip, flat or spike-like. Leaf sheaths rounded, typically rough towards the top. Leaf ligule membranous, 1-4mm long, acute at apex. Flower spike open and spreading at anthesis and contracting at fruiting. Spikelets tiny, 1.6-3mm, clustered towards the tips of very fine branchlets with a single floret in each spikelet. Lemmas may or may not be awned.
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Brown Bent Agrostis vinealis
A native perennial typically found in dry places on acidic soils and most frequent in heathy places, in association with heather and gorse. Flowers June to August. Plants 10-60cm in height and spreading by slender, scaly rhizomes to form tufted patches. Leaf blades 1-5mm wide, hairless, finely pointed at the tip, flat or bristle-like. Leaf sheaths rounded, typically rough towards the top. Leaf ligule membranous, 1-5mm long. Flower spike generally narrower and less open at anthesis than other bents. Spikelets tiny, 2-2.3mm, clustered towards the tips of very fine branchlets with a single floret in each spikelet. Lemmas usually awned but occasionally unawned.
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Loose Silky-bent Apera spica-venti
A native or perhaps neolithic introduction, mostly confined to sandy soils in Breckland and the Suffolk Sandlings where it mostly grows on disturbed ground in arable crops. Flowers June to August. Plants annual, 20-100cm in height. Leaf blades 3-10mm wide, hairless, pointed at the tip, flat. Leaf sheaths rounded, often rough towards the top. Leaf ligule membranous, 3-10mm long. Flower spike open and very diffuse, 10-25cm in length. Spikelets tiny, 2.4-3mm, single-flowered, spread further along the fine branches than is the case with the true bents. Glumes slightly to strongly unequal in size. Lemmas 2.4-3mm, as long as or slightly shorter than the upper glume with a 5-10mm awn. Anthers 1-2mm long. A distinctive and graceful grass, often strongly overtopping the crop in which it is growing. Small plants can sometimes be hard to tell from Dense Silky-bent excpet by measurements of the lemmas and anthers.
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Dense Silky-bent Apera interrupta
A native or perhaps neolithic introduction, mostly confined to sandy soils in Breckland. Flowers June to July. Plants annual, 10-90cm in height. Leaf blades 1-4mm wide, minutely hairy or rough on the veins above, smooth beneath, pointed at the tip, flat. Leaf sheaths rounded, often rough towards the top. Leaf ligule membranous, 2-5mm long. Flower spike narrow and upright, 3-20cm in length. Spikelets tiny, 1.8-2.5mm, single-flowered, spread further along the fine branches than is the case with the true bents. Glumes unequal in size. Lemmas 1.8-2.5mm in length, as long as or slightly shorter than the upper glume with a 4-10mm awn. Anthers tiny, 0.3-0.4mm long.
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Silver Hair-grass Aira caryophyllea
A native annual, widespread on a wide range of dry and sandy or acidic soils; most common on acid heaths and dunes but also along railways, dry tracks and paths. Flowers May to July. Plants 3-30cm in height, more typically at the lower end of the size range in dry habitats. Leaves 0.3-0.4mm wide, greyish-green, thread-like and inrolled and soony reddening in dry conditions. Leaf sheaths rounded. Ligule membranous, up to 5mm long, jagged at the tip. Flower spike compact at first, but fully open and wide-spreading at anthesis, 1-12cm in length. Spikelets 2.2-3.5mm, each with 2 florets. Glumes relatively large, 2.2-3.5mm, enclosing the florets. Lemmas awned from the back. A tiny grass that typically grows in small, scattered colonies, but can be easily overlooked due to its small size.
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Wavy Hair-grass Avenella flexuosa
A native perennial, confined to dry, acid heaths. Often abundant and can dominate large areas in ideal habitat, such as in the Suffolk Sandlings, Norfolk heaths and Breckland. Flowers June to July. Plants 20-90cm in height, forming tight tussocks. Leaves 0.3-0.8mm wide, narrow, inrolled. Leaf sheaths rounded. Ligule membranous, 0.5-3mm long, blunt at the tip. Flower spike flexuous, at first with branches held close together, but later open and broadly spreading, up to 15cm in length. Spikelets 4-6mm, each usually with 2 florets. Glumes very thin, almost membranous. Lemmas 3-5.5mm, membranous, awned. A very distinctive grass with the stems tinged pinkish-purple and the shiny spikelets waving in unison in the breeze.
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Tufted Hair-grass Deschampsia cespitosa
A native perennial, frequent to common in woodland glades and shady places on heavier soils and land prone to being wet in winter. Flowers June to August. Plants 10-200cm in height, forming a large and dense tussock, often in colonies. Leaves 2-5mm wide, flat or rolled, green, hairless, strongly ribbed above. Leaf sheaths rounded or slightly keeled, smooth. Ligule membranous, long, up to 15mm in length. Flower spikes tall, graceful and open, 5-50cm in length with many spikelets. Spikelets 2-6mm, 2-flowered, clustered towards the ends of thin and sinuous branchlets. Glumes about as long as the spikelet, membranous and shiny. Lemmas 3-8mm, membranous, toothed at the tip.
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