Edmonds Marsh invader threatens ecosystem health

Snohomish County Noxious Weed Control Coordinator Geraldine Saw shows marsh advocate Greg Ferguson the differences between Phragmites and the more common Reed Canary Grass.

No one is sure how it got here. Some say it came from Asia, others Europe. But regardless, it has found a home in the Edmonds Marsh where it is slowly but inexorably creating dense stands of tall reeds that are pushing out native vegetation and degrading wildlife habit.

Phragmites australis is found worldwide. The name Phragmites (pronounced in three syllables, Frag-mite-ease) is derived from ancient Greek, roughly translating as “grows in hedges,” a reference to its tendency to form thick stands around waterways and marshy areas.

Saw demonstrates the tough, fibrous stems and leaves of Phragmites that make it unsuitable for wildlife forage.

According to the U.S Fish and Wildlife Service fact sheet, the non-native Phragmites (there is also a mostly rare, non-invasive species native to our east coast) was first observed in North America in the early 19th century in coastal ports in the eastern United States. The rapid spread of Phragmites in the 20th century was probably related to the construction of railroads and major roadways, habitat disturbance, shoreline development and pollution.

The original stand of Phragmites in the Edmonds Marsh was first identified six years ago. Since then, it has spread significantly.

Phragmites was first observed in the Edmonds Marsh six years ago, in a small stand in the northeast quadrant. Since then, this stand has grown into a dense jungle of these 8- to 10-foot-tall reeds, so thick that birds, furbearing mammals and even deer cannot penetrate. More recently it has spawned a second stand just south of the viewing area at the end of the boardwalk adjacent to the railroad tracks. The plants are too rough for forage and tend to crowd out other plants that support wildlife.

The plant spreads mostly by deep underground horizontal stems call rhizomes (while underground, rhizomes are actually stems, not roots) and lateral ground-hugging stems called stolons (see illustration).

This diagram illustrates how Phragmites spreads expands via underground rhizomes and above-ground stolons.

It can also spread by seeds that are typically water-borne, which is the likely origin of the second stand in the Edmonds Marsh.

Earlier this week, a small group including marsh advocates and elected officials met at the Marsh with Geraldine Saw, Noxious Weed Control Coordinator for Snohomish County, to observe the stands of Phragmites and discuss strategies for control.

– Snohomish County Noxious Weed Control Coordinator Geraldine Saw explains how Phragmites out-competes native plants and degrades habitat.

Explaining that mechanical control is virtually impossible due to the deep and complex root and rhizome systems, Saw recommends control by chemical herbicides as the safest and most effective method.

“We use Imazapyr, a U.S. Department of Agriculture and Department of Ecology-approved systemic herbicide that targets the roots of the plants,” she explained. “It degrades within three to four weeks, and when properly applied has no significant effect on other plants or wildlife.”

The second stand of Phragmites in the Edmonds Marsh is located near the railroad tracks along the western edge of the Marsh. It was probably spawned by seeds carried by water from the original stand.

She went on to explain that the county’s team of licensed applicators would apply the herbicide directly to green Phragmites foliage.  The active ingredient is absorbed into the plant and is translocated via its vascular system to all plant tissue – particularly the stolons and nutrient-rich rhizomes – where it kills Phragmites by de-activating a protein found only in plants. Treated plants will begin to yellow, turn brown and die within about 3 weeks.

“We add a blue dye to the spray that allows quick visual determination of where it has been applied,” she added.

She then explained that treating the Phragmites in the Edmonds Marsh would be quick, requiring about two to three hours. The first application will typically kill about 80% of the stand, and a second application during the next growing season generally gets the remaining 20%.

Because Imazapyr can affect other plants as well, Saw recommends application well in advance of the fall rains, thereby minimizing the chance of increased water flows spreading it beyond the target plants before it has sufficient time (three to four weeks) to naturally degrade.

“Summer is already on the wane, so would be nice if we could do this as soon as possible,” she said.

In order for the application to happen, the county needs approval from the City of Edmonds. Saw plans to prepare a letter to the mayor and city council asking for this.

— Story and photos by Larry Vogel

  1. Pesticides are not a longterm solution; repeat applications of chemicals do not correct degraded conditions. The goal must be restoration of healthy native vegetation, not just removal of non-native invasives, such as Phragmites and Lythrum (aka Purple Loosestrife, not mentioned in this article but readily seen in the marsh). Aerial applications of Imazapyr are historically controversial. Ground application poses lower risk. However, the Wash. State Noxious Weed Control website says, “Cutting (Phragmites australis) has been used successfully for control . . . Cutting can be used for successful control by cutting it just before the end of July when most of the food reserves produced that season are removed and the aerial portion of the plant reducing the plant’s vigor. This regime may eliminate a colony if carried out annually for several years.”

    1. Spray it and Spray it now. It’s too late, the seeds are sewn. They will and are continually growing as I type. It appears now it will spread more. Forget that 22 acres that are questionable. The way this area has been studied and studied why they didn’t report the first one they saw is beyond my comprehension.
      Can someone tell us when it was first spotted and what was done.

  2. Japanese knotweed and purple loosestrife are exotic invasive plants that have been in the marsh for decades. Why are these not also a subject of concern and action? What about the horse chestnut and mountain ash trees that are now growing in the marsh? When do they get removed? They are non-native trees that spread easily. Our reliance on chemical eradication often fails and frequently causes harm we haven’t anticipated. The poor marsh and its poor wildlife . . .

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