Weeding Out Threats to Salmon Habitat
The Reed Canary Grass Story
It’s hard to believe that a non-native grass, introduced to the Kenai Peninsula because of its useful properties, could wipe out salmon habitat. That’s precisely what’s happened, though, in salmon streams and wetlands from California to British Colombia when a grass known as reed canary grass has gotten near them.
The Culprit
Reed canary grass was brought to the Kenai Peninsula for use as a soil stabilizer and as a forage crop. It is preferred by some hay farmers because of its ability to grow in wet, heavy soils where other grasses won’t grow. It has long been recommended for use in revegetation of roadsides and utility corridors because it spreads rapidly, forming a dense sod that prevents soil erosion.
Why Attack?
It’s these very properties, though, that make reed canary grass such a threat to our wetland and stream ecosystems. Reed canary grass thrives in many of the same habitats as our native bluejoint grass, which is commonly found along stream banks. One major difference between the two is that bluejoint is a clumping grass, while reed canary is a sod-forming grass. The distinction lies in how an individual plant grows. A bluejoint plant grows by adding new shoots around the perimeter to form an ever-larger clump (also called a hummock). Reed canary grass, like other sod-forming grasses, expands by sending out underground rhizomes. The rhizomes can extend for several feet underground, sending up new shoots at intervals along the way. Many individual plants form the tightly-knit network that we call sod.
For salmon streams, this is an important distinction. Bluejoint grass, which has been growing on the Kenai Peninsula for thousands of years, won’t grow into a stream channel. When the stream channel is narrow and the hummocks on either side of it are large, the hummocks will meet one another over the channel, allowing the stream to flow unimpeded beneath. Reed canary grass, on the other hand, sends its rhizomes into the soil under the stream and sends up shoots into the stream channel. As the grass fills in, the channel itself can widen out and become indistinct. This causes a number of problems for stream dwellers, and particularly for spawning salmon.
In 1999, one hundred fifty-eight dead pre-spawn cohos were found in an abandoned reed canary grass pasture in King County, Washington. Investigators determined that the fish had been trying to swim upstream through a grass-choked channel running through the field. During a high-water event, the stream fanned out into the pasture and the salmon, unable to find the main channel, became stranded in the field as the water receded. Because of the widespread habitat destruction caused by reed canary grass, Washington has classified it a class C noxious weed.
Some have suggested that because of our harsher climate, reed canary grass may not produce viable seed here and won’t spread beyond where it’s planted. Both these assertions have been proven false. To determine whether its seed was viable, the Alaska Plant Materials Center collected seed from 17 reed canary grass populations around the Kenai Peninsula and conducted germination trials. The results showed an average germination rate of 83%, showing that reed canary grass does produce highly viable seed here. The Kenai Watershed Forum and the Kenai and Homer Soil and Water Conservation Districts have done extensive surveying and mapping of reed canary grass on the Peninsula. Those efforts have shown a clear pattern of reed canary grass spreading downstream along our creeks and into undeveloped natural areas.
The Plan of Attack
In order to address this growing threat, the Kenai Watershed Forum in 2008 began efforts to control reed canary grass near waterways. That work has continued this year, and progress is being made. You can help by keeping an eye out for this invasive grass and reporting it, especially where you see it near waterways. It’s becoming easier to spot now that fall is upon us because it stays green (with dried out, beige-colored seed heads) long after other plants have died back for the winter.
Contact Michelle Martin at Kenai Watershed Forum, 262-5469 or michelle@kenaiwatershed.org.
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Reed Canary Grass Identification
Reed canary grass looks similar to timothy and smooth brome, common hay species, and bluejoint, a native grass. All of these have green leaves, grow fairly tall, and can be found along roadsides, on stream banks, and in open fields. Here are some distinguishing features of reed canary grass:
- Leaves are brighter green than bluejoint
- Leaves are usually broader than other local grasses
- Leaves are held erect, less drooping than other species
- Can grow over 8 ft. tall (others usually don’t grow over 5 ft.)
- Remains green (with beige seedheads) into the fall, when other plants are dying back for the winter
- Has a different flower shape than other grasses. When the flower heads emerge in summer, they appear to be unbranched, but the branches open up over the course of the season. In late summer and fall, the flower heads turn from green or purple to a pale beige as they dry out. The branches of the flower head fold up again as the plant goes to seed.
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| RCG Plant - Summer | RCG Plant - Fall |
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| RCG Flower Head - Open | RCG Flower Head - Closing |
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| RCG Flower Head - Closed | Timothy Flowers |
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| Smooth Brome Flower | Bluejoint Flower |
Project Partners
Alaska Dept. of Fish and Game
Kenai Peninsula Borough
UAF Cooperative Extension Service
U.S. Forest Service
U.S. Environmental Protection Agency
U.S. Fish and Wildlife Service
National Park Service
Homer Soil and Water Conservation District
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