More info for the terms: cover
, fire management
, nonnative species
, prescribed fire
In many of its nonnative habitats, common velvetgrass is not described as a serious weed; however, many studies indicate that common velvetgrass' allelopathic potential, rapid early development, litter accumulation, response to disturbances, and nutrient additions can negatively impact associated native vegetation.
Impacts: Common velvetgrass is referred to as a problematic species in Hawaii but is often considered a species of lesser concern in other parts of its nonnative North American range. In reviews from the Hawaiian Islands, common velvetgrass is considered "disruptive" and described as "forming dense stands that appear to inhibit recruitment of natives" . Establishment on disturbed sites in Hawaii is often rapid . Invasiveness ratings of common velvetgrass are likely relative; when associated with more invasive weed species, it is less likely to be described as a problem.
Throughout most of its nonnative range, common velvetgrass is either not listed on invasive plant lists [56,94] or is referred to as a "minor weed" , not a "major problem species" , moderately invasive , or "not readily invading natural areas"  as of this writing (2009). Although prevalent in Oregon and Washington, common velvetgrass is absent from many invasive species lists for the area . Common velvetgrass is not listed in the Invasive Plant Atlas of New England , although it is well established in the area. Potentially problematic common velvetgrass growth characteristics are discussed below; these may result in impacts that affect a local scale in the nonnative range.
Allelopathy: In laboratory tests, common velvetgrass showed possible allelopathic properties. When common velvetgrass and garden sorrel (Rumex acetosa) seedlings were grown in sand that was collected beneath a common velvetgrass monoculture, growth of both species was "markedly depressed" as compared to controls, even when nutrients were added (Al-Mashhadani and Grime, personal communication, cited in ). Germination and radicle extension were significantly lower for bulbous canarygrass (Phalaris aquatica) and orchardgrass (Dactylis glomerata) seeds kept moist with water containing common velvetgrass leaf extracts than for those kept moist with deionized water (P=0.001) .
Rapid early growth: Rapid germination and seedling growth may allow common velvetgrass establishment and spread in a variety of habitats. In a greenhouse experiment, the maximum relative growth rate of common velvetgrass was 2.01/week. Soon after seedling establishment, 4 weekly harvests were made to calculate this growth rate, which was high compared to other species evaluated . In another greenhouse experiment, growth rates of common velvetgrass were 42 mg and 65 mg/g/day in low- and high-nitrogen environments, respectively. Growth rates were calculated from 10 weekly harvests .
Early germination and rapid seedling growth may allow for the development of stable common velvetgrass stands that limit the growth of associated species. Fifty days after seeding, common velvetgrass seedlings produced the greatest dry weights of 6 western Oregon pasture species grown in the greenhouse . When seeds collected from coastal prairie in northern Marin County, California, were monitored in growth chambers, common velvetgrass germinated more rapidly than red fescue. However, the final germination rate of red fescue was 60% higher than common velvetgrass . Common velvetgrass biomass was significantly greater than that of Hawaii's alpine hairgrass after 6 months of growth in low-light/low-nutrient, high-light/low-nutrient, and low-light/high-nutrient treatments (P<0.05). In high-light/high-nutrient conditions, alpine hairgrass biomass was greater than that of common velvetgrass, but not significantly. Common velvetgrass allocated more biomass to roots than did alpine hairgrass .
In greenhouse and field experiments, common velvetgrass was most abundant, had the highest growth rate, and, as a seedling, was the most resistant to invasion when compared to other British Columbia pasture species. In the greenhouse, common velvetgrass was most abundant in patches established from seed. Seedling patches resisted invasion most. Based on comparisons made with common velvetgrass tillers collected from older pastures, researchers characterized common velvetgrass as an "r-type" species that likely requires repeated colonization opportunities to maintain a viable population in pastures . In patchy coastal prairie vegetation in California, patches of common velvetgrass inhibited establishment of other species when seed was introduced. Although some seedlings emerged in common velvetgrass patches, none of these produced seed within 2 years of establishment. In patches of nonnative annual grasses, common velvetgrass establishment was successful. An input of 12,442 common velvetgrass seeds/0.25 mÂ² produced 39.2 common velvetgrass seedlings/0.25 mÂ². Newly established individuals in annual grass patches produced up to 21 seeds/0.25 mÂ² and 5.1 seedlings/0.25 mÂ². Common velvetgrass also had some establishment in perennial grass patches, but none of these plants produced seed within 2 years .
A common velvetgrass monoculture established in the field near Bristol in the United Kingdom severely restricted the growth of European white birch (Betula pendula) seedlings. One year following planting, the diameter of European white birch seedlings averaged 2.8 mm when grown with common velvetgrass and 8.4 mm in the absence of common velvetgrass. Seedling heights averaged 8.7 inches (22.2 cm) with and 24.7 inches (62.7 cm) without common velvetgrass .
Litter accumulation: In California grasslands, high productivity and reduced litter decomposition in common velvetgrass grasslands may affect regeneration potential and species composition. On the Bodega Marine Reserve in Sonoma County, California, common velvetgrass stands (aboveground biomass 836 g/mÂ²) were more productive than annual grassland stands (aboveground biomass 534 g/mÂ²). Standing litter accumulations in common velvetgrass stands were 1,537 g/m² and in annual grasslands were 766 g/mÂ². From exclusion experiments, researchers learned that the dominant detritivore in the area, Porcellio scaber, did not consume common velvetgrass litter. Increased litter in common velvetgrass stands could affect seedling recruitment as well as fuel loads, fire potential, and fire behavior . In field studies in coastal prairie in northern Marin County, California, common velvetgrass litter decreased germination of native grasses more than that of common velvetgrass. Under 0.4 inch (1 cm) of litter, common velvetgrass germination was about 50% lower than germination on bare soil; however, germination of common velvetgrass was still significantly greater than that of Pacific hairgrass, red fescue, Pacific reedgrass (Calamagrostis nutkaensis), and purple needlegrass (Nassella pulchra) (P-value not reported). Under 1.2 inches (3 cm) of litter, common velvetgrass and native grass germination were not different .
Control: While several methods may be useful to control common velvetgrass, it is likely that severe defoliation and repeated treatments may provide the best control. Evaluation of associated vegetation and potential increases in these species may affect management decisions. In a greenhouse study using monocultures of 6 grasses and 4 legumes, researchers found that introduced thistle seed (Carduus nutans and Cirsium vulgare) emergence was lowest in common velvetgrass stands . Management decisions in common velvetgrass' nonnative habitats may involve making value judgments between nonnative species.
Some researchers suggest that marking common velvetgrass treatment areas in the early morning when dew is trapped in its velvety hairs may help to focus control efforts and minimize nontarget effects .
Photo taken in Maui, HI,
©Forest and Kim Starr
Flooding/salinity: Common velvetgrass experienced high mortality when partial dike removal occurred in a 15-year-old pasture on the Salmon River Estuary in Lincoln County, Oregon. Cover of common velvetgrass was up to 70% in the pasture before dike removal. In the 1st growing season after dike breaching, common velvetgrass suffered high mortality and averaged less than 5% cover. By the 2nd growing season, common velvetgrass was essentially absent. Before dike removal, salinity in the pasture was 0 to 3 ppt and after breaching was 11 to 39 ppt .
Fire: For information on the use of prescribed fire to control this species see Fire Management Considerations.
Prevention: Methods that may limit the establishment of common velvetgrass in lawn or pasture plantings are discussed by Fitzsimmons and Burrill .
Physical and/or mechanical: Some suggest that hand-pulling and hoeing, while labor intensive, can decrease common velvetgrass abundance . A review reports that intense grazing or mowing may limit common velvetgrass establishment and spread . Mechanical methods to control common velvetgrass are described by Fitzsimmons and Burrill .
It is important to note that mowing equipment has the potential to disperse common velvetgrass seed. After mowing in a common velvetgrass-dominated grassland in the Netherlands, 86% of the seeds removed from the mower were common velvetgrass seeds .
During controlled studies conducted outdoors and in a greenhouse, short cutting heights and increased cutting frequencies decreased common velvetgrass yield. When plants were cut between mid-March and early May, regrowth produced panicles by July 8, but when cut in early June, no panicles were produced on regrowth .
In the Willamette Valley, mowing and cutting led to increased common velvetgrass inflorescence production. Plants were mowed short, cut to the base twice, or burned twice in the fall. Mowing and cutting increased the reproductive potential of common velvetgrass. Fire generally decreased inflorescence production; details are discussed in the Western United States section of Fire Ecology :
Changes in the number of common velvetgrass inflorescences/plant between pretreatment and first growing season after 1st and 2nd treatments [26
] Treatment Mowed to 8-12 cm heights Cut at base Fall fire Control Difference between pretreatment and 1st year after single treatment +4.45 +1.34 -0.7 -0.38 Difference between pretreatment and 1st year after 2 treatments +11.50 +5.46 -0.7 -0.80
Biological: No information is available on this topic.
Chemical: Herbicides potentially useful in common velvetgrass control are discussed in the following reviews: [46,134,161]. McHenry (1985, cited in ) suggests herbicide treatments may be most effective in the spring or when the first seed head appears because translocation to the roots is likely at that time.
Integrated management: A review suggests that mowing or grazing combined with prescribed fire treatments may decrease common velvetgrass dominance .