Invasive Plants of California's Wildland

European beachgrass (Ammophila arenaria) is a perennial rhizomatous grass occurring in coastal dunes. Stems are clumped, stiff, and upright. Leaves are twelve to forty-four inches long, thick and waxy. The outer surface is smooth and light green; the inner surface has ridges and is covered with a whitish coating. Leaves are often rolled at the edges, covering ridges on the inner side, and leaf tips are pointed and sharp. The inflorescence is cylindrical, six to twelve inches long on stiff, erect stems. Rhizomes are tough. Leaves are narrower, stiffer, and lighter in color than the native beachgrass, Leymus mollis.

European beachgrass occurs on sandy coastal dunes from British Columbia to San Diego County, California (Breckon and Barbour 1974, Barbour and Johnson 1977). The plant thrives in unstable dunes where there is continuous sand accretion, but it is also found in stabilized dunes. While European beachgrass appears to spread actively north of San Francisco, it is not as aggressive to the south (Barbour et al. 1976, Barbour and Johnson 1977). However, it is reported as invasive at Guadalupe-Nipomo Dunes in San Luis Obispo County.

European beachgrass is native to the coast of Europe and North Africa, from Scandinavia south to the Mediterranean Sea, and from Great Britain east to Egypt. It was first planted along the Pacific Coast of North America, around San Francisco's Golden Gate Park, in 1869. It has since been transplanted elsewhere along the coast (Barbour 1970), and there may also have been subsequent introductions from its native range. It was planted extensively to stabilize dunes.

European beachgrass spreads almost exclusively by rhizomes, which can extend laterally over 6.6 feet (2 m) in six months (Aptekar, 1999). Rhizomes are also washed by ocean currents to new sites, where new populations can become established. The rhizomes can survive and sprout new plants after being submerged in seawater for prolonged periods. Bud viability is still 51.2 percent after seven days of submergence, and 8.5 percent after thirteen days submergence (Aptekar, 1999).

European beachgrass forms a dense cover that appears to exclude many native taxa. Plant species diversity on beaches dominated by European beachgrass is much less than that of beaches dominated by native beachgrass (Breckon and Barbour 1974, Barbour et al. 1976, Pavlik 1983c, Boyd 1992). As European beachgrass cover increases, the cover of native plant species decreases significantly (Aptekar 1999).

Dunes dominated by European beachgrass also have lower arthropod species diversity, and fewer rare arthropod species than dunes dominated by native species (Slobodchikoff and Doyden 1977). The reduction in the amount of open sand areas in dunes dominated by European beachgrass has severely reduced nesting habitat for the federally listed threatened western snowy plover (Charadrious alexandrinus) (Pickart and Sawyer 1998).

European beachgrass directly threatens native plant communities, including Leymus mollis dominated foredunes (Pitcher and Russo 1988) and dune mat communities (Van Hook 1983, Pickart 1988, Pitcher and Russo 1988, Buell et al. 1995, Wiedemann and Pickart 1996, Pickart and Sawyer 1998), as well as the endangered Menzies' wallflower (Erysimum menziesii) and other rare dune species (Van Hook 1983, Pickart and Sawyer 1998).

European beachgrass has changed beach topography, creating steep foredunes where none were present prior to its introduction, and altering dune formation to promote dunes that are parallel to the coast, whereas under native grasses, dunes formed roughly perpendicular to the coast (Cooper 1967, Barbour and Johnson 1977, Wiedemann and Pickart 1996).

European beachgrass primarily reproduces vegetatively through rhizome growth. Plants are initially established by plantings undertaken to stabilize dunes, and by rhizomes washing in on ocean currents from other sites. Once plants are established, they expand their territory through vigorous rhizome growth. European beachgrass rarely becomes established by seed. Seedlings are occasionally found, but most die from desiccation, burial, or erosion. Seedlings are most likely to survive in dune slacks where the sand surface remains damp (Huiskes 1977, Benecke 1990).

European beachgrass is able to withstand up to 3.3 feet (1 m) a year of sand burial (Huiskes 1979), which is greater than what the native beachgrass, Leymus mollis, appears to tolerate. Sand burial of European beachgrass promotes leaf and internode elongation, as well as growth of vertical rhizomes from axillary buds on horizontal rhizomes (Gemmell et al. 1953). In areas without sand accretion, it is much less robust (Wallen 1980). European beachgrass uses nitrogen more efficiently, and allocates more resources to producing leaves and shoots, than does L. mollis (Pavlik 1983). Shoots grow most vigorously in spring. Growth slows during winter, but does not cease entirely (Huiskes 1979).

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European beachgrass is a rhizomatous perennial grass that grows most vigorously under conditions of continued sand accretion, and forms extensive monospecific stands. The plant produces both vertical and horizontal rhizomes. New shoots arise mainly along the vertical rhizomes, forming dense tufts of grass. Horizontal rhizomes are responsible for lateral growth.

Manual methods: European beachgrass can be removed by intensive repeated digging. Successful manual control at Lanphere-Christensen Dunes Preserve (Pickart and Sawyer 1998) required weekly to monthly digging of European beachgrass from early spring through fall. If sand was "sifted" with rakes to remove rhizome fragments for a depth of 19.5 to thirty-nine inches (0.5 to 1 m) following digging, follow-up treatment was not required the following year. If sand was not sifted following digging, and plots were dug monthly or less frequently, a second year of monthly digging was required. On foredunes, where European beachgrass grows more vigorously than in inland stands, a third year of monthly digging was required. In general, less follow-up digging was required when first-year treatments were more frequent, more thorough, and/or larger or in less dense locations (so that fewer plants re-invaded from surrounding stands).

Mechanical methods: Some attempts have been made at Oregon Dunes National Recreation Area to remove European beachgrass with heavy machinery. In the most ambitious attempt, European beachgrass was removed to a depth of approximately one meter (3.3 feet). The removed material was buried and capped with up to one meter of sand. Moderate resprouting occurred the following spring (Pickart and Sawyer 1998).

Prescribed burning: Burning stimulates European beachgrass to resprout, and so by itself does not appear to be effective in eradicating it (Pickart and Sawyer 1998).

Flooding: Several attempts have been made using salt water or seawater to eliminate European beachgrass (Pickart and Sawyer, 1998). In small test plots in 1983 at Lanphere-Christensen Dunes Preserve, seawater treatments were not effective and rock salt treatments had inconclusive results. A large-scale project using seawater irrigation to control European beachgrass on twenty-six acres (10.5 ha) of the North Spit of Coos Bay, Oregon, in 1996 was not successful (Pickart, pers. comm.).

Insects and fungi: No insects or fungi have have been approved by the USDA for control of European beachgrass in the United States. There is no recorded insect that feeds solely on European beachgrass. Meromyza pratorum Meigen (Dipt., Chloropidae), a beetle, feeds only on European beachgrass in western Europe, but it has been found feeding on wheat in Russia and Italy. The larvae destroy vegetative points, killing up to 30 to 40 percent of tillers (Huskies 1979). Many fungi have been recorded as living on European beachgrass, but most of these are non-specific saprophytes or weak parasites on dying parts of the plant.

Grazing: Animals native to California beaches rarely graze on European beachgrass. Even if an animal could be found that would graze on the plant, it would not be an effective control, since European beachgrass resprouts from its numerous below-ground buds and rhizomes.

In experimental trials conducted in northern California from 1991 to 1994, using a variety of herbicides, the only foliar treatment that consistently reduced live European beachgrass cover by 90 percent or more was glyphosate (as Roundup®), applied at concentrations of 4 percent or 10 percent and mixed with 0.5 percent added surfactant (Citowett® or Silwet L-77® were used) applied at 200 gallons per acre (Aptekar 1999).