Authors: Tunyalee Martin, Global Invasive Species Team, The Nature Conservancy
(Leers) Coss. & Durieu
The generic name Ventenata honors the french botanist Pierre Ventenat (1757-1805). The common names "wiregrass" and "hairgrass" describe the plant's form.
Ventenata dubia has established itself in a number of states in the USA and provinces in Canada. It is currently expanding from Washington and Idaho to the Idaho-Nevada border near Duck Valley. It invaded Utah in 1996. Its expansion in the Pacific Northwest will probably continue via transportation as a contaminant in grass seed.
The impacts of this new invader are unknown. However, V. dubia has the following characteristics:
- It is weedy in disturbed areas such as alongside roads and in fields.
- It is highly invasive in bluegrass, alfalfa, winter wheat, pasture and rangeland.
- It can impede mechanical harvesting equipment.
Ventenata dubia (Leers) Durieu. is an introduced tufted annual grass. The stem is erect, 1.5-7 dm, and appears smooth, although tiny hairs are noticeable when magnified. The leaf ligule is 1-6 mm long and the blade is 1-3 mm wide. Inflorescences are panicle-like, 3-10 cm long and open. The branches often spread until they droop. Spikelets (10-15 mm long) are near the branch tips and are stalked. The glumes are lancelolate, and end in a sharp tip. The lemmas have bent awns arising from their backs, much like those of wild oats (Avena barbata, A. fatua). The upper 1-2 florets are bisexual.
Ventenata dubia is similar in appearance to Bromus tectorum (cheatgrass). Both grasses are annuals, similar in height and have open panicles. Ventenata dubia spikelets are much like those of Avena, with bent awns, 2-3 florets per spikelet and larger glumes ending in a sharp tip. In contrast, B. tectorum has straight awns, 3-6 florets per spikelet, and smaller glumes. Ventenata dubia flowers from June to August, while B. tectorum flowers earlier in the year, from May to June.
Ventenata dubia germinates best at moderate to high temperatures. An experiment at different temperatures found 24%, 93%, and 50% germination at 8°, 18°, and 28°C respectively; the number of days to achieve 75% germination was 6 days at 18°C, 10 days at 28°C, and 13 days at 8°C (Northham & Callihan, 1986). In Wisconsin, V. dubia plants were near-flowering on June 14, and by July 5 all plants had produced mature fruit and died.
Ventenata dubia is native to central and southern Europe, Asia, and Africa.
As an invader, Ventenata dubia has been found in California (Siskiyou Co., southern Nevada Co., at 1200-1500 m elevation), Idaho, Montana (Mineral Co.), Nevada, Oregon (Polk Co.), Utah (Elmore Co.), Washington, and Wisconsin (Oconto Co.). In Canada it has been found in Ontario, Quebec (Missiquoi Co.) and British Columbia. While many papers cite the first North American record of V. dubia as being a 1964 Idaho collection by Baker, Old & Callihan (1987) state the first occurrence was in Idaho in 1957. Some authors  maintain that V. dubia has not been found in Nevada (but cf. Old & Callihan, 1987). Expansion in the Pacific Northwest will no doubt continue, and may be accelerated by its spread as a contaminant in crop grasses grown for seed.
Control methods have not been developed for this relatively new invader.
- It is an annual, so the focus must be on reducing or stopping seed production.
- Ventenata dubia has demonstrated resistance to glyphosate and sethoxydim.
- Mowing may be ineffective since this grass tends to bend rather than cut.
- Palatability is low and so grazing may not be an option.
- Solheim, S.L. and E.J. Judziewicz. 1984. Four noteworthy Wisconsin plants. Phytologia, vol. 54, no. 7.
- ↑ Old, R.R. and R.H. Callihan. 1987. Ventenata dubia in the Pacific Northwest. Proceedings of the Western Society of Weed Science, vol. 40:130. 2.0 2.1
- Malone C. 1999. Another Weed. Northern Nevada Native Plant Society Newsletter vol. 25, no. 2:1-2.
- Allen, L. and M. Curto. 1996. Noteworthy Collections - Utah. Madrono vol. 43:337-338.
- Chambers, K.L. 1985. Pitfalls in Identifying Ventenata dubia (Poaceae). Madrono, vol. 32, no. 2:120.
- Hickman J.C., ed. 1993. The Jepson Manual, p. 1302. University of California Press, Berkeley.
- Northam, F.E. and R.H. Callihan. 1986. Germination of four annual grass weeds at three temperatures. Proceedings of the Western Society of Weed Science, vol. 39:173.
- NHIC List of Ontario Vascular Plants (nhic.mnr.gov.on.ca/mnr/nhic/species/listout.cfm)
- Watson, L. and Dallwitz, M. J. 1992 onwards, Grass Genera of the World: Ventenata