Invasive Plants & Glencoe Swale

Friends of Glencoe Swale are grateful to Rob Emanuel, Ph.D. for his knowledge, enthusiasm, and support. His presentation at our February 2016 meeting inspired much reflection, pertinent questions, and thoughtful conversation…


What are invasive plants?

Rob defined invasive plants as noxious, harmful, and overwhelming. More than ordinary “weeds,” invasive plant populations are explosive. Once spread begins, invasive plants get a hold in ecosystems that are very expensive in terms of the environmental, health, and economic damage they cause.

Invasive plants displace native species. Impacts include:  fragmentation of habitat, disease, changes in stream water quality and soil health, and hydrology dynamics to list a few.

Why should we care?

Charts illustrated the economic burden invasive plant mediation and restoration projects place on society at city, state, and national budgets. Can you image? An average of $10.00 person is estimated as the yearly cost to tackle this pervasive problem.


Learning about and understanding the effects of invasive plants is part of the collective knowledge-base citizenry, government, and industry need to make sound ecological decisions at both the home and community levels.

In our community, the quality of the Tualatin River valley watershed is of primary focus. Rob referred to the Tualatin as the mother ship for Glencoe Swale, and the other creeks/streams that flow into her. Work on watershed quality is looked at by Clean Water Services as a holistic endeavor. Back in the 1970’s many sewer districts dumped into the Tualatin… to a point that water quality got so bad that a building moratorium was declared. Unified Sewage was formed to address point and non-point sources of water contamination. Clean Water Services took over in 1990 with an emphasis on using natural systems to improve Tualatin River water quality.

Rob is proud of the fact that Clean Water Services does not use mechanical means to cool and improve water quality. He said, “Care about trees!”

What can we do?

At this juncture, Rob honed in on what groups like ours can do to improve watershed quality. We were inspired by restoration work he told us about in the Bronson Creek watershed. This creek system is very similar to Glencoe Swale. He shared a photograph of the restored area. It inspired hope, questions, and thoughtful conversation.

Photo of Rob Emanuel’s original in PowerPoint presentation.

Rob encouraged us to plant trees and native plants. Over time, they will process nutrients, give shade to improve water temperature, replace invasive plants, and provide organic input for eco-system health.

He also described the restoration process… the goal? Return environment to similar conditions that were in an area 100 years ago. Invasive removal techniques include hand and chemical removal- depending on the situation. An important aim… do no harm to animals dependent on the watershed. Work before breeding season. The work in the Bronson Creek watershed took two years of site preparation: removal of invasives using hand, mechanical, and chemical means. Native vegetation growth as shown in the photo above took: 1 year and counting…

Friends of Glencoe Swale received a targeted mini-lesson on the invasive plants and native plants we can expect to remove, replace, and find in our watershed systems:

Reed Canary Grass

  • very difficult to remove,
  • changes soil and water chemistry to kill other (native) plants,
  • expands territory by growing in “leap-frog” islands,
  • prevents or changes water flow,
  • originally from Eurasia, now hybridized.

English Ivy

  • changes environment by choking trees, causing them to fall,
  • ivy overtakes forest,
  • easily spread through seeds broadcast in bird poop, especially English Starling.


  • introduced as a commercial agriculture industry,
  • seeds spread,
  • berries become toxic to songbirds over time.

English Laurel

  • bird born problem

Armenian/ Himalayan Blackberry

  • introduced into North America on East Coast of the United States in 1885 by Luther Burbank,
  • established on West Coast by 1945,
  • now the bane of the Pacific Northwest… highly invasive,
  • micro-climate forms inside large bramble patches and creates its own climate for growth,
  • with tenacity, can be hand-removed… key- whack out and pry out root crown.

Lesser Celandine

  • dig this one up!
  • throw bulblets in trash can… do not compost.

Purple Loosestrife

  • if found, report finding to Rob.

Giant Knotweed

  • originally from Japan, Korea, China,
  • this invasive cannot be removed by hand- pieces cause further spreading,
  • if found, alert Rob!
  • this species was found and treated by SOLVE at Glencoe High School in 2014.

Yellow Flag

  • native from Eurasia,
  • forms large colonies,
  • very fast growing.

Others mentioned- Yellow Archangel, Old Man’s Beard, Italian Lord and Ladies.

To dispose of invasive plants that have been removed from Glencoe Swale watershed:

  • throw seeding plants, plants with bulbs- into garbage can. Do not compost these.
  • herbacious pieces can go into garden debris recycle bin.

Native Plants

Rob showed slides of a number of native plants that flourish or will potentially flourish in the Glencoe Swale watershed and riparian areas.  An excellent reference booklet, “GardenSmart Oregon: a guide to non-invasive plants” was provided, along with many other references, for folks to take home with them.

Further Training/Actions

  • Rob provided flyers with contact information for Oregon State Extension Service,
  • Suggested attending a “Weed Watchers” class this spring,
  • Attend/participate in a “Tree for All” event,
  • Create areas of Nature-scaping in yards… especially properties that border or contain Glencoe Swale wetland or riparian zones.

In closing, Rob encouraged us to “Work bigger than we can.” He also believes in the practice of working from the upper to lower watershed areas in the scaled restoration process… build a wildlife corridor!