Family Poaceae | Class C Noxious Weed
Reed canarygrass (RCG) is a rhizomatous, sod forming, cool-season (C3), long-lived perennial grass in the Poaceae Family. Cool season (C3) grasses, grow well as long as temperatures are mild, but their photosynthesis becomes inefficient at high temperatures. RCG produces dense crowns, prominent networks of rhizomes, and monotypic stands that currently dominate portions of many riparian areas in the Hood Canal. RCG is widespread throughout most of North America including Washington State (King County, 2015; Roche et al., 2019; Lavergne & Molofsky, 2006; Miller, Martin, & MacConnell, 2008; Roche et al., 2019).
Native to temperate zones of the Northern Hemisphere, RCG is widely distributed throughout Eurasia. Not completely nonnative to North America. A few wild populations predate European settlements in North America, but these populations were not considered aggressive. Exotic and native forms occur in North America, however there is no reliable way to tell the difference between native and introduced populations (Lavergne & Molofsky, 2004; Roche et al., 2019; King County, 2015).
Most strains of RCG commonly encountered in North America act as a typical invasive plant and are thought to have originated as cultivars bred for high productivity and stress tolerance, or as hybrids between native genotypes and those cultivars. Non-native European cultivars were introduced into the Pacific Northwest shortly after 1850 for hay and forage and continued to be introduced for uses including: perennial cover for permanent pastures, soil stabilization along stream banks and shorelines, erosion control, wastewater treatment and biomass production (Hovick & Reinartz, 2007; Lavergne & Molofsky, 2006; King County, 2015; Lavergne & Molofsky, 2004).
RCG has spread throughout North America, taking over natural wet prairies, streambanks, and wetlands. It constitutes a major threat to native riparian and wetland plant communities and is classified as a pest in nine states in the US (Lavergne & Molofsky, 2006). RCG is one of the most damaging invasive wetland grasses in Pacific Northwest and is able to rapidly spread and take over plant communities replacing diverse plant assemblages with monospecific stands, drastically reducing species diversity (Lavergne & Molofsky, 2006; Roche et al., 2019; King County, 2015). Studies continue to document RCG’s ability to decrease native species diversity through competitive exclusion. However, it is unlikely that allelopathy is the mechanism responsible for invasion success of RCG (Lavergne & Molofsky, 2004).
RCG’s prolific root system, high nutrient uptake capacity, relatively high water use efficiency, high stem elongation and leaf production, early emergence and persistent productivity into the fall, provides a competitive advantage allowing it to dominate both above and below ground resources (Lavergne & Molofsky, 2004).
RCG can clog waterways, increase sedimentation, alter water circulation, and reduce micro topography heterogeneity; which ultimately leads to the loss of valuable habitat for fish and wildlife. (Lavergne & Molofsky, 2006). By growing vigorously on streambanks, forming monospecific stands in floodplains, and clogging waterways RCG slows water flow which induces sedimentation potentially degrading salmonid spawning habitat (Miller, Martin, & MacConnell, 2008). The dense growth can form physical barriers to salmonid migration and flooded RCG fields have been known to confuse and strand migrating salmon; one RCG infestation caused conditions that resulted in the stranding and death of 158 prespawn male and female Coho in a western Washington stream (Miller, Martin, & MacConnell, 2008; King County, 2015).
RCG can outcompete native plant species, resulting in monospecific stands with subsequent loss of plant and insect diversity and ultimately to alteration in ecosystem function (Lavergne & Molofsky, 2006). RCG provides little food for native wildlife species and causes indigestion in livestock (King County, 2015). Few animals will eat the grass after flowering because of its rank growth, and most waterfowl are unable to use infested habitat for nesting, food, or cover (Miller, Martin, & MacConnell, 2008). RCG invasion could potentially impact streamside aquatic and terrestrial insects which are an important food source for rearing juvenile salmon. Very low soil insect diversity was observed in marshes dominated by monocultures of RCG, when compared to adjacent marshes dominated by native species (Lavergne & Molofsky, 2004).
RCG dominated communities that were historically forested are especially resistant to reestablishment of the original vegetation, presumably because of a lack of establishment sites. Grasses in particular can limit the establishment and growth of woody species (Hovick & Reinartz, 2007). The thick sod layer, and aggressive growth eliminate safe sites for establishment of native woody shrub and tree species. Over time canopy cover is reduced, which decreases stream shading and increases water temperatures (Hovick & Reinartz, 2007). Overtime, large woody debris recruitment into the stream channel is also reduced, which provides critical salmon habitat for returning adults and rearing juvenile salmon.
When in flower, RCG produces abundant pollen and chaff, which can aggravate hay fever and allergies; that poses a human health hazard (WA State NWCB).
Hovick, S. M., & Reinartz, J. A. (2007). RESTORING FOREST IN WETLANDS DOMINATED BY REED CANARYGRASS: THE EFFECTS OF PRE-PLANTING TREATMENTS ON EARLY SURVIVAL OF PLANTED STOCK. The Society of Wetland Scientists, 27(1), 24-39. Retrieved November 23, 2020.
King County. (2015, February). King County Noxious Weed Control Program Best Management Practices: Reed Canarygrass. Retrieved November 19, 2020, from https://your.kingcounty.gov/dnrp/library/water-and-land/weeds/BMPs/Reed-Canarygrass-Control.pdf
Lavergne, S.; Molofsky, J. (2006). Control Strategies for the Invasive Reed Canarygrass (Phalaris arundinacea L) in North American Wetlands: The Need for an Integrated Management Plan. Natural Areas Journal, 26(2), 208-214. Retrieved November 20, 2020, from https://www.jstor.org/stable/43913893.
Lavergne, S., & Molofsky, J. (2004). Reed Canary Grass (Phalaris arundinacea) as a Biological Model in the Study of Plant Invasions. Critical Reviews in Plant Sciences, 23(5), 415-429. Retrieved November 23, 2020.
Miller, T. W., Martin, L. P., & MacConnell, C. B. (2008). Managing Reed Canarygrass (Phalaris arundinacea) to Aid in Revegetation of Riparian Buffers. Weed Science Society of America, 22(3), 507-513. Retrieved November 20, 2020, from https://www-jstor-org.ezproxy.library.wwu.edu/stable/pdf/25195077.pdf?refreqid=excelsior%3A43483534ad2ef6adb471af3939794b3e.
PNW Weed Management Handbook. Reed Canarygrass – Phalaris arundinacea. Retrieved November 23, 2020, from https://pnwhandbooks.org/weed/problem-weeds/canarygrass-reed-phalaris-arundinacea-ribbongrass-phalaris-arundinacea-var-picta
Roche C. T., Brainerd R. E., Wilson B. L., Otting N., Korfhage R. C. (2019). Field Guide to the Grasses of Oregon and Washington. Oregon State University Press. Corvallis, OR.
Waggy, Melissa, A. 2010. Phalaris arundinacea. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://www.fs.fed.us /database/feis/plants/graminoid/phaaru/all.html [2020, December 18].
WA State Noxious Weed Control Board. Reed Canarygrass-Phalaris arundinacea. Retrieved November 23, 2020, from https://www.nwcb.wa.gov/weeds/reed-canarygrass