Agrostis capillaris is a tufted perennial C3 tetraploid grass. It is variably described as reaching heights of 20-25cm (IPAO, undated) 70cm (NZPCN, 2010) or 100cm (Edgar & Forde, 1991). Roots have rhizomes and occasionally stolons. Leaves are flat, short and narrow measuring 100-150 x 1.5mm. Ribs and regular and margins slightly rough (NZPCN, 2010). The entire plant is hairless (Garry Oak Ecosystems Recovery Team, 2003). Spikelets (flower clusters in grasses) are 1.5-3.5mm in length and purplish brown to greenish in colour (Edgar & Forde, 1991). Seed heads are usually 15cm long with spreading branches with tiny, brown seeds (NZPCN, 2010). It is a long-day plant with floral initials forming early May in the Northern hemisphere, with flowering peaking early July (Philipson, 1937 in Rapson & Wilson, 1992). A detailed description of the plant can be found in Edgar and Forde (1991).\r\n\r\n

A. capillaris is a highly variable species; plants can differ greatly in size, habit, presence of absence of stolons or rhizomes, type of inflorescence and in spikelet structure. Some of this variation may be the result of hybridisation with A. stolonifera and A. castellana (Edgar & Forde, 1991).

Agrostis capillaris is often referred to in many scientific articles and research as Agrostis tenuis. The accepted name according to ITIS is A. capillaris, while A. tenuis remains a synonym it is commonly found and incorrectly labeled as the primary name (ITIS, 2008).\r\n\r\n

A. capillaris is highly variable with many cultivars recognised. There is wide phenotypic and genotypic variation in populations (Grime et al., 1988). Common bent forms hybrids with creeping bent (A. stolonifera).

Agrostis capillaris has an active growth period in spring and summer accompanied by blooms midway through. Fruit and seed production begins at the same time blooms appear which lead to dispersal of A. capillaris seeds (USDA, NRCS, 2008).\r\n\r\n

In the Northern hemisphere flowering begins in early June, with flowering peaking in early July). Anthesis (time when flower is open and fully functional) occurs about 14 days after first emergence of inflorescences (Philipson, 1937 in Rapson & Wilson, 1992). In New Zealand inflorescence emergence occurred in December-January with anthesis occurring about 26 days later. There were some latitudinal trends with more southerly populations flowering earlier (Rapson & Wilson, 1992).

Agrostis capillaris, like many other members of the Agrostis genus are a valuable agronomic species because of their ability to produce fodder as well as provide food for grazing animals (APHIS, undated). A. capillaris is also used for tennis courts, high-grade lawns, golf course fairways and erosion control (Hubbard, 1984 in Zhao et al., 2006).

Agrostis capillaris is known to invade disturbed areas and also frequently grows along roadsides (Manual, undated). A. capillaris is also abundant in wetlands including moist grasslands and open meadows as well as cultivated areas (IPAO, undated). It is frequent on acid grassland, damp soils, meadows, pasture and rough ground (Stace 1997 in Bond et al., 2007). In a study done in Oregon, A. capillaris was 10 times as abundant in areas after prescribed burn versus that of an unburned area (Wilson, 1999). It 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 (Dale et al., 1965). It is tolerant of temperature extremes and can grow at a range of altitudes from coastline up to 2,200 metres in British Columbia (Garry Oak Ecosystems Recovery Team, 2003) and 2106 m in Australia (Pickering & Hill, 2007).

Agrotis capillaris propagates by way of highly abundant seeds and vegetatively by rhizomes and stolons. The large proportion of A. capillaris clones and low proportion of seedlings in populations suggests that much of its reproduction is vegetative (Smith, 1972 in Wilson, 1988). Flowers are wind pollinated, but are also spread by water, humans and vertebrates (Timmins & MacKenzie, 1995 in NZPCN, 2010). Seed is set from August to October in the northern hemisphere (Grime et al., 1988). Seeds may persist for 5 years or more (Thompson et al., 1993).

Agrostis capillaris has a lack of tolerance for magnesium, and therefore has difficulty growing in areas of higher magnesium concentrated soils like seashores (Wu, 1981). It can grow on dry, low fertility soils (Rapson & Wilson, 1992) and has high tolerance to heavy metals (Wilson, 1988) and arsenic (Watkins & Macnair, 1991). It does, however, require high light levels (Rapson & Wilson, 1992b).

Agrostis capillaris impacts native biodiversity in its known introduced range by out competing and replacing native species (Johnston, 2001). The spread of A. capillaris has decreased the cover of native herbs in some New Zealand grasslands, leading to reductions in endemic grassland moths (White, 1991). Agrostis capillaris adapts in two main ways to environmental stresses: by adapting genetically, and through plasticity. In New Zealand Rapson and Wilson (1992, 1992b) showed A. capillaris populations to be highly plastic, which may give adaptive advantages in New Zealand’s unpredictable and small scale environment and contribute to its invasiveness (Rapson & Wilson, 1992b).\r\n\r\n\r\n

A. capillaris is also a known carrier of the Barley yellow-dwarf virus (BYDV), which reduces populations of native grasses in New Zealand (Davis, 2001).

Physical: The use of prescribed burning has shown a dramatic increase in growth of Agrostis capillaris, so is not an effective management tool (Wilson, 1999). Similarly grazing is not effective due to its low growth form. Grazing can even increase abundance (Garry Oak Ecosystems Recovery Team, 2003). Mechanical removal by hand pulling, ploughing, grubbing and harrowing can reduce common bent and prevent seeding. This method is most effective in spring or early summer before seed set. Control by manual removal is however labour intensive and can be difficult due to broken stolons which can develop roots and regrow (Garry Oak Ecosystems Recovery Team, 2003). Short rotations with root crops may help reduce the weed (Bond et al., 2007).\r\n\r\n

Chemical: The gramicides cycloxydim and fluazifop-p-butyl have been used in the effective management of A. capillaris (Clay, 2006). A. capillaris is also susceptible to the herbicide dalapon (Evans, 1964). A study found that the application of the herbicide BAS 9052 OH on A. capillaris produced a 100% mean control rate (Hosaka, 1984). Glyphosate applied to soil before emergence of A. capillaris has been found to be effective in reducing growth (Salazar, 1982). Hexazinone has also been used in successful treatment and control of various weed and grass species including A. capillaris (White, 1990).\r\n\r\n

Biological: There are no known biological agents available for A. capillaris (Garry Oak Ecosystems Recovery Team, 2003; Froude, 2002).