Preventing Biological Invasions is a Gardener’s Responsibility

Herb Robert is a common garden invader and problem for its ability to move around with garden soil, plants, pets and clothes. Photo by R. Emanuel.

Most gardeners are unaware that they often inadvertently play roles in the spreading invasion of noxious weeds. But they also can learn to avoid, guard against and eliminate plants that try to escape the boundaries of their gardens.

“Biologists estimate that between 30 and 80 percent of invasive plant species introduced to the United States originated as garden plants,” said Linda McMahan, one of the authors of a new Oregon State University Extension publication, “Invasive Species: What Gardeners Need to Know,” EM 9035, available online at

“In Oregon alone, 21 designated noxious weeds cost approximately $125 million a year in production losses, fire damage and control,” she said. Researchers have determined that almost half of the 1,000 plants and animals protected under the U.S. Endangered Species Act have been listed because of biological invasions.

Plant invasion occurs in three distinct phases:

Introduction. Gardeners can introduce and establish invasive species as they bring a new plant into their garden and perhaps share it with neighbors through plant or seed exchange. The plant population may experience a lag time in its reproductive ability, in which it will stay in a controlled situation such as a garden, forest or pasture. The plant does not appear to be overly aggressive. In some cases, the lag period can persist for decades.

Escape. During the second phase, an escaped plant appears to jump out of the garden into the neighboring landscape. Often this means a plant has overcome barriers that have kept it in check and prevented its spread. These barriers may include temperature, moisture, pests or competition from other plants.

Invasion. Eventually, the plant population shows signs of invasion. During this phase, the plant rapidly reproduces by sexual means (seeds) or asexual means (roots/rhizomes or creeping stems) and may spread over large distances.

The OSU Extension publication points out that gardeners can take control over the introduction and escape phases of a new invasion if they evaluate their potential plant choices first. “Responsible consumers can become informed prior to making a purchase,” McMahan said. Several websites can point the way (see below).

Sometimes a plant’s invasive potential can be arrested by watching it grow in the garden. When a plant starts to show an ability to escape the designated garden or landscape boundaries, the gardener needs to deadhead, trim or otherwise prevent the plant from escaping.

If someone gives you a start or seed, ask where the plant is from and if it is native to Oregon. How successful was the plant in the garden? Does the plant produce many seeds that sprout more than a few feet away from the original plant?

What are the alternatives to invasive species? The publication strongly recommends that they be replaced with Pacific Northwest natives and advises how to get rid of invasive species already in the garden. Many nurseries carry and order more native plants than previously, McMahan said.

Websites to help identify invasive species:

•  Oregon Department of Agriculture’s Oregon State Noxious Weed List is an authoritative listing of plants officially designated as noxious weeds in the state.

•   Oregon Public Broadcasting’s Silent Invasion website provides a photographic list of invasive species of concern in Oregon.

• The United States Department of Agriculture Natural Resources Conservation Service’s PLANTS Database allows the user to track plants for their occurrence in individual counties throughout 49 states. Users can use the website to determine whether a plant is invasive by referring to the Invasive and Noxious Weeds page.

• Closer to home (for me), Clean Water Services maintains a website with a focus on identifying non-native invaders in our area.

• Also, check out the 4 County Cooperative Weed Management Area and their compendium of Portland-area weeds:

•   The University of Montana’s Invaders Database System allows users to search for invasive species by name, state or area in the five northwestern states or access lists of noxious weeds for all U.S. states and six Canadian provinces.


Got Knotweed? New OSU publication offers solutions.

Note, this is a reposted press release by Judy Scott, OSU Extension and Experiment Station Communications. And yes, this is my publication listed below so if you have questions, please contact me directly.

Giant knotweed spreads in a coastal community in Oregon.

Giant knotweed spreads in a coastal community in Oregon. Photo by R. Emanuel, OSU.

If ever a case needs to be made against introducing non-native plants to a new area, “woody knotweed” says it all. Like a sci-fi beast from outer space, woody knotweed seemingly wants to take over the Earth.

Imagine a weed that you can’t pull, cut or mow because you’ll encourage denser new growth.

Woody knotweed reproduces itself readily from small pieces of its own roots and stems and can contaminate the soil in which it grows. Knotweed-infested soil is considered a hazardous material in the United Kingdom.

A new Oregon State University Extension publication called “Biology and Management of Knotweeds in Oregon: A Guide for Gardeners and Small-Acreage Landowners” explains that the plant cannot be reasonably managed by non-chemical means. The publication is online and free of charge at Continue reading

Don't Move a Mussel in the PNW!

Just last month, Oregon Department of Fish and Wildlife inspectors discovered zebra mussels attached to a Michigan-based recreational boat arriving in Oregon at the Ashland Port of Entry. This was a strong wake-up call that the devastating mussels are on their way. It will only take one boat and one organism to infest Oregon waters.

US Fish and Wildlife Service have produced this video for helping show how easy it is to spread the mussels and how easy it is to prevent that spread into our state’s precious waterways.

To learn more about zebra and quagga mussels and programs aimed to prevent and detect their invasion, visit:

Invasive Species in the PNW Blogosphere!

Gorse. Photo by Lynn Ketchum, OSU EESC

I’ve not gotten around to it but as they say, there’s no time like the present–kudos to Dan Hilburn for publishing the Oregon Invasive Species Blog! Dan has been publishing this semi-weekly since last April and I’ve been remiss in my attention to spreading the word (not the weeds) about it. So apologies to Dan and some big blue stars for the excellent work.

While it may be cold and wet outside, the green (plant) invaders are just waiting for the right time to return to our attention. The snails, insects, turtles, nutria, and tunicates are still very much alive and well.  So don’t forget about them.  Learn more and head over to Dan’s useful blog.

“The future ain’t what it used to be.” –Yogi Berra

Saturday 10/23 watershed events highlight Meds, Knotweed and Stormwater

Saturday is a busy one for those of us with an interest in watersheds and water! Come sample one or more of these three regional events that were you can gain knowledge and aid the health of NW Oregon watersheds.

1. All About Knotweed: Come learn more about woody knotweeds and how to manage an invasion. Participants will get hands-on identification of the plant types, learn plant and invasion biology, learn to create a management plan and learn the latest treatment options. This class is offered in cooperation with Oregon Open Campus. Participants may sign up for Continuing Education Credits for Pesticide Applicators via Tillamook Bay Community College.

When: Saturday, October 23rd, 8:45 -10:30 AM
Where: Tillamook Bay Community College, Room 104/105.
Cost: $20.00
Call 503-842-3433 for more information or to register and pay.

2. Tillamook County Medicine Collection Event: Tillamook County Solid Waste Department is sponsoring a pharmaceuticals collection event. Keep your unused and expired over-the-counter and prescription meds out of our environment and away from accidental or intentional misuse by adults, teens, and children.

When: Saturday, October 23, 9:00 AM-12:00 PM
Where: Tillamook County Fairgrounds, Sheriff’s Department Booth
For more information contact Jennifer Purcell at (503) 814-3975 or Kaylee Haertel at (503) 322-2222.

3. Welcome the Rain: Portland-area residents can find out about a variety of ways to manage their landscapes, rain and stormwater to benefit the environment during this annual event sponsored by East Multnomah Soil and Water Conservation District. Geared to address the community’s growing desire for more information on urban stormwater issues, Welcome the Rain! offers information and resources for participants to explore ways to help improve water quality for people, fish and wildlife. OSU will be there to talk about opportunities become a Master Watershed Steward.

When: Saturday, October 23,  10am – 3pm
Where: Atkinson Elementary – 5800 SE Division, Portland OR 97206
Call EMSWCD for more information:  (503) 222-7645

New Invaders, New Training for N. Coast Volunteers

Clatsop County Early Detection of Invasives Network (CCEDIN) is hosting two trainings for agency personnel and volunteers this month (June 19 for the public and June 24 for ODF personnel only). Below is my presentation from these trainings.   Thanks to the National Park Service and Clatsop Soil and Water Conservation District for pitching in to make these events highly successful! Happy weed-watching this field season!

Invader Alert: colonial tunicates invade Oregon coastal waters.

CORVALLIS, Ore. – An aggressive, invasive aquatic organism that is on the state’s most dangerous species list has been discovered in both Winchester Bay and Coos Bay, and scientists say this “colonial tunicate” – Didemnum vexillum – has serious economic and environmental implications.

Invasive colonial tunicate photo

Colony of invasive colonial tunicates (Didemnum vexillum) photographed on the Oregon coast by Lorne Curran.

Its propensity to foul surfaces of boats, fishing nets, water intakes, docks and buoys could make it costly to control, and its ability to smother shellfish beds and sensitive marine environments threatens other marine life.

“This is not a welcome addition to our bays and now the clock is ticking,” said Sam Chan, an invasive species specialist from Oregon State University and chair of the Oregon Invasive Species Council. “The fouling potential from tunicate invasions can be severe, given its ability to reproduce asexually by budding, or breaking off as fragments, and through sexual reproduction where tadpoles emerge, swim and attach themselves to surfaces to form new colonies. Continue reading

Weighing Costs and Risk of Quagga and Zebra Mussels in the Columbia

Photo courtesy of Michigan Sea Grant College Program.

Zebra and Quagga Mussels will cost PNW energy ratepayers a lot of money concludes a draft study by Northwest Power and Conservation Council’s Independent Economic Advisory Board. It will also cost other users of the river and its tributaries including agricultural irrigators, municipal water suppliers, marina owners, and fish hatcheries.  Though the study isn’t due out until June, this is a big step towards quantifying the threat of aquatic invasive organisms like Quagga and Zebra (Dreissenid) mussels, so reports the Columbia Basin Fish and Wildlife Bulletin.

“During its January meeting the Nation Power and Conservation Council [NPCC] tasked the IEAB with analyzing potential economic effects of a quagga or zebra mussel infestation of the Columbia River basin with a focus on the Federal Columbia River Power System and the NPCC’s fish and wildlife program.

The IEAB’s final report, which is due in June, should help the Council and other policy makers in the region better understand the potential damage and related costs of a mussel infestation as compared to the potential cost of preventative actions. Mann was in Boise to give the Council a progress report on the project.”

The Bulletin goes on to list some of the areas that could be impacted by a mussel infestation:

“The IEAB is gathering information on possible impacts to infrastructure within the Council’s sphere of influence, including any submerged components and conduits of the FCRPS, including juvenile and adult fish passage and monitoring facilities, navigation locks, hydropower facilities, raw water distribution systems for hatcheries, turbine cooling, and water supply; trash racks, diffuser gratings, and drains.

Non-FCRPS [Federal Columbia River Power System] irrigation, municipal water supply and other infrastructure could also be affected, and a mussel invasion also has the potential to collapse the existing food chain.

There are no known zebra or quagga infestations in the Pacific Northwest but they seem to be moving closer and closer. The invasive mussels were found in January 2007 in Lake Mead in the Southwest and since then quagga or zebra mussels have been found in Arizona, California, Colorado, Nevada, Texas and Utah.”

In the Columbia system, however, there are still plenty of questions about whether the organisms can survive in our low calcium waters or under different types of stream conditions.  The results of a study in the Frontiers of Ecology and the Environment published on-line in by OSU’s Thom Whittier and others shows that these European mussels don’t thrive unless waters are still and calcium levels are high.  Many of the streams and lakes of Western Oregon and Washington are therefore, probably low risk in terms of infestation. But uncertainties remain, as they did in the Colorado River system before the mussels arrived there and proliferated, despite some of the indications otherwise.

Image courtesy of Thom Whittier, OSU Department of Fisheries and Wildlife.

What have these organisms cost other, comparable areas?  In the Great Lakes area–the location with the longest history of infestation, mussels have cost the power industry about $3.1 billion between 1993 and 1999 according to Congressional researchers. Overall community impacts totaled at least $5 billion according to the Quagga-Zebra Mussel Action Plan for Western U.S. Waters.

The point of this is that for quagga and zebra mussels, as well any other aquatic invader, risk–biological, physical and economic–needs to be determined to better prepare for invasions.

If you know the enemy and know yourself, you need not fear the result of a hundred battles.  If you know yourself but not the enemy, for every victory gained you will also suffer a defeat.  If you know neither the enemy nor yourself, you will succumb in every battle. — Sun Tzu, “The Art of War”

Invasive species for PNW green industry professionals

This week, I am presenting at the High Desert Green Industry Conference and at Sunriver Resort on invasives. At these events I’m focusing on how green industry professionals (landscapers, designers, installation contractors, maintenance contractors) can integrate an understanding of invasive species into their work.

The green industry is often in an awkward position with regards to invasive species. They are often tagged with the primary responsibility for new invasive introductions. At the same time, it is the gardening public who create demand for new and exciting introductions or for bringing invasives into new environments though their activities in and outside of the garden. Often, once a horticultural plant is deemed invasive, the industry feels itself under siege as regulators demand the industry give up a plant. Additionally, interest groups and the general pubic may then demand that the industry toe the line, and convert to new non-invasive stock such as natives–even where natives may not be entirely appropriate (such as in highly urbanized settings).  All of this leaves an industry that should be a part of the solution  feeling divorced from the efforts to “do the right thing” with regards to invaders.

But there are some easy solutions.  My take-home messages for green industry professionals includes some simple–but not mutually exclusive–actions:

  • Know the invasive species in your area & teach the public and your peers about them
  • Research new stock before you order it
  • Grow, sell or design for native & non-invasive plants wherever possible
  • Help the public with information on treatment
  • Get involved in landscape management ordinances where appropriate
  • Get involved in weed management boards
  • Help support local weed identification and education efforts
  • Help support research focused on invasive plant ecology, control and alternatives
  • Watch for hitchhikers in nursery stock
  • Use weed-free soil and mulch
  • Watch introductions for aggressive behavior
  • Discourage use of commercial wildflower or other mixes.
  • Check clothes, vehicles, equipment, & pets when working in infested areas.

Here are some of the resources I presented to the participants in these events:

Below are other resources that I compiled for professionals and gardeners alike:

Lastly but not least, are some published guides to Pacific Northwest and regional invaders as well as their more environmentally friendly alternatives: