Common bent
Other names
Common bent-grass, brown bent, colonial bent, fine bent, highland bent
Latin names
Agrostis capillaris L. (Agrostis tenuis Sibth, A. vulgaris With.)
Weed Type
Perennial Grass Weeds
Occurrence
Common bent is a native rhizomatous, perennial grass, common and widely distributed particularly on acid grassland, damp soils, meadows, pasture and rough ground. Common bent grows on nutrient poor meadows, heathland and forest gaps. It is characteristic of upland pasture in short turf. It is recorded up to 3,980 ft in the UK.
Common bent has a preference for poorly drained, fine to medium textured soils of pH 6.5 to 7.3 with a moderate level of organic matter. It is a calcifuge and invades areas of poor acid soils. It can establish quickly after soil disturbance, vegetation clearance or burning. In set aside land in Scotland common bent was the most abundant grass in unsown fields and represented around 10% of the total ground cover. It is an important constituent of upland sheep pastures in regions of high rainfall. However, the shoots wither in late summer and it is of limited grazing value in some pastures.
There is wide phenotypic and genotypic variation in populations. There are also many cultivars. Common bent forms hybrids with creeping bent (A. stolonifera).
Biology
Common bent flowers from June to August. The flowers are wind pollinated and seed is set from August to October.
In laboratory tests with seeds maintained under high or low light intensity or in darkness, seeds gave around 80% germination in the light and 54% in the dark. Germination was greater at alternating temperatures in the dark than at constant temperatures. In the field, seeds germinate in autumn and spring.
Common bent propagates by both seed and rhizomes. The rhizomes lie just below the soil surface and do not penetrate deeply. They are much thinner than the rhizomes of common couch.
Persistence and Spread
It is suggested that based on seed characters, common bent seed is likely to persist for longer than 5 years. Unlike most grasses, the seeds have been recorded in large numbers in the soil beneath pastures. Seed buried in mineral soil at 13 cm depth and left undisturbed retained 28% viability after 4 years but none was viable after 20 years. Seed buried in a peat soil at 26 cm for 1, 4 and 20 years retained 18, 3 and 0% viability respectively. Seed remained viable for over 7 years in dry storage but in soil all but 1.8% had germinated or perished within 7 years. The loss was most rapid in the first 3 years. Seed stored under granary conditions exhibited 72% viability after 1 year, 2% after 4 years and 3% after 20 years. The few seeds that survived storage for 20 years produced apparently normal seedlings when germinated.
Common bent seed has been recovered from irrigation water in the USA. The seeds are consumed by earthworms but viable seeds have not been recovered from wormcasts.
Common bent spreads vegetatively by short rhizomes and stolons.
Management
Control of common bent is by ploughing, grubbing and harrowing. Seeding must be preventing and hedgerows kept free of the weed. Short rotations with extra root crops will help to combat the weed. The chief aim is the removal of the creeping stems. Isolated patches may be forked out and burnt. Smother crops of maize, vetches or mustard will assist in choking out the weed.
Under frequent cutting, common bent produces small tillers close to the ground. It exhibits some tolerance to burning. In permanent grassland, the percentage cover of common bent was reduced following fertilizer application. Seed numbers in the soil seedbank were also reduced. In permanent grass, common bent will soon appear under severe grazing and within 5 years it can make up a significant proportion of the sward. Control is by liming, good manuring and cutting before seeding.
Common bent is grazed by rabbits and this inhibits flowering.
Updated October 2007.