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Participant information (all fields are required)


The product label of the herbicide you are using
An online video tutorial produced by King County
Guidance from your local weed control program
Advice from Uncle Larry

2, 4-D

Bohemian (hybrid)
Japanese (itadori)

Glyphosate is the active ingredient
The type of site where you will be applying the herbicide is listed on the product label
The label contains instructions for hollow stem injection
All of the above

Shorts and a tank top
Coveralls and a face mask
A hazmat suit
It will be listed on the label of the product you are using

As early in the growing season as possible
Late in the growing season, but before the first frost
After the first hard freeze, when the plant has gone dormant


The herbicide you will be treating with
Rubbing alcohol

The top-most internode on the plant
Internodes around waist-height
The second or third internode from the ground
Knotweed doesn’t have internodes

The injector needle splits the stem wide open
The stem is smaller than your pinky finger
The internodes look too small to hold the injected dose of herbicide
All of the above

All appropriately sized stems
Every third stem of knotweed
One stem per clump of knotweed
One stem per ten square feet of knotweed

All appropriately sized stems
Dump the remainder in a nearby creek
Distribute over your newly landscaped lawn
Consult the label for appropriate disposal

Three times
None, you’re too tired from injecting weeds to care

Your name
The time it took you to complete treatment
The approximate square footage treated
The approximate location of the area treated
All of the above

Related information

Related agencies

Program offices are located at 201 S. Jackson St., Suite 600, Seattle, WA 98104. To contact staff, see the Noxious Weed Control Program Directory, send an email, or call 206-477-WEED (206-477-9333).