Plant Identification: What is that Weed?

Do you think you’ve found a noxious weed?  Here is how you can get help to identify and report your find!

One of the most important aspects in controlling invasive weeds is to verify the identification if invasive weeds before you work to control them.  Knowing the difference between an aggressive weed and a common native is important to ensure you aren’t harming desirable plants.

Get familiar with your flora

The first step in recognizing invasive plants is to start seeing them.  If you are not familiar with the plants in your area, it is time to put on those walking shoes and head outside.  This may seem obvious, but if you aren’t familiar with plants in your area, you won’t be able to recognize them when they are out of place or when a new plant is introduced.  Getting to know the plants growing in your area also connects you to the natural world around you.

Develop a discerning eye

To build some familiarity with your local flora, practice noticing the plants that surround you when you hike, walk, ride and paddle. Pay attention not just to the colorful flowers, but to interesting leaf patterns and shapes, the texture of the leaf surfaces and the stem, the height and form of the plants.  All of these are helpful identification features and they’re also incredibly beautiful and diverse.

Do your homework

Use local plant guides and keys to identify your plants.

Once you begin to notice the fine differences between plants, it is time to start checking your observations against field guides and keys.  First spend some time familiarizing yourself with how your guide is organized.  Practice your skills by grabbing some common plants that you may already know and working through the key with them.   Some good beginner plant identification field guides include:

  • Plants of the Pacific Northwest Coast, J. Pojar & A. MacKinnon
  • Trees & Shrubs of the Pacific Northwest, M. Turner & E. Kuhlmann
  • Wildflowers of the Pacific Northwest, M. Turner & P. Gustafson

More technical botanical keys include:

  • The Flora of the Pacific Northwest, l. Hitchcock and A. Cronquist
  • Plants of Western Oregon, Washington, and British Columbia, E. Kozloff
  • Flora of Oregon Volume 1: S. Meyers, T. Jaster, K. Mitchell, and L. Hardison (eds).
  • Jepson eFlora. Jepson Flora Project (eds.)

There are also a number of weed specific field guides available for FREE.

Recognize invasiveness

Even if you are not confident in your skills identifying plants, you can still detect invasive plants by learning to recognize plants that are growing aggressively or out-of-balance.  The first step is to look for plants that form large dense stands that appear to be displacing surrounding vegetation.  These invasive plants also tend to spread very quickly on the landscape.  Also, look for plants that show aggressive growth across a variety of settings.  Plants that are adapted to full sun to shade, moist to dry, or across a large range of soil types can indicate an invasive plant.

Know when to get help

Use a common object to help denote scale.

When you see plants that display invasive characteristics, try to identify the plant using one of the identification guides listed.   If you aren’t confident in your botany skills, there are a number of ways to get a plant identified.  You can bring a sample or send pictures to the WeedWise program or to the local soil & water conservation district or noxious weed control district in your area.

When collecting samples or sending photos use these following guidelines:

  • When collecting plants and photos make sure they represent others found in the area.  Some plants can be variable in their growth, so collect a representative sample of specimens.
  • Avoid collecting plants that have been previously cut or damaged. These injuries can alter growth and make them more difficult to identify.
  • When collecting specimens be sure to collect all aspects of the plants. For trees collect branches that include leaves, flowers, and/or fruits.  Record observations like plant height, location, and site conditions. For smaller plants collect the entire plants including the roots!
  • Bring plants in while they are still fresh. wilted samples become exceedingly more difficult to identify as they deteriorate.
  • If submitting a photo, be sure that your images are in focus. Take an image of the entire plant, as well as close-ups of leaves, stems, fruits or seed, flowers, roots, or any other prominent features.  Include items such as a ruler, coin, pen, or person in a photo to help the reviewer determine scale.  Also, be sure to take a photo of the area in which the plant was found.  This will help determine growing conditions that might favor one plant over another.
  • Be aware. There are some rare native species which occur infrequently on the landscape. If you aren’t sure of the identification of a plant, only collect a specimen if there is a healthy population present.
  • Also, be aware that photos can be more difficult that physical specimens to identify.  A reviewer may need to request a live specimen to ensure more accurate identification.

Get assistance identifying plants from your local experts.

Another great resource to help with plant identification is the OSU Extension Clackamas County Master Gardeners or your local master gardener chapter.  These dedicated volunteers are a great resource for general plant and gardening information.   If you are still having troubles identifying a plant, submit a sample to the pros at the OSU Plant Clinic.

Identity is more than just a name

Once you have determined the identity of your plant sample, your next step is to learn about its impacts.  Check out the WeedWise program weed list for weed designations and profiles.

The Oregon Department of Agriculture also maintains a list of invasive plant profiles.  Many cities and counties also maintain nuisance plant lists which may be searchable online to help you determine whether to take action to control a problem invasive plant.

Report your observation

If you see a plant of concern, you should check out the WeedWise reporting page or submit them directly to the Oregon Invasives Hotline. Your reports help local weed managers to  treat new damaging invaders while populations are still small.

For additional assistance with plant identification contact these resources.

Clackamas Soil & Water Conservation District

22055 S Beavercreek Rd

Beavercreek, OR 97004


[email protected]

Clackamas County Master Gardeners

200 Warner–Milne Rd.

Oregon City, OR 97045


[email protected]

Oregon State University Plant Clinic

Department of Botany and Plant Pathology

Cordley Hall 2082

Corvallis, OR 97331-2902


[email protected]

, , , , , , , , , ,

WeedWise Program