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The City of Portland, Oregon

Environmental Services

working for clean rivers

Phone: 503-823-7740

Fax: 503-823-6995

1120 SW 5th Ave, Suite 613, Portland, OR 97204

More Contact Info

What is being done about it?

The City of Portland has  begun its garlic mustard treatments for 2021.  We hire licensed contractors to do some of this work.  All are operating under coronavirus guidelines.

Plants have been appearing in multiple phases this year, possibly due to low rainfall in March and April.  At this point, plants are still in flower, but should be exiting that stage soon.  The soil is pretty dry, so handpulling plants (on PRIVATE property, please) will require a little extra care.  That may change with the late week rains.  If you would like to pull roadside plants, please make arrangements with the city beforehand, so we don't miss plants that re-grow later in the year.   

Please continue to watch this page for the latest on garlic mustard and its treatment. 

(last updated: 5/5/21 MRB)

Areas treated by Environmental Services so far include: 

Areas Managed in 2021

Treatment Date

SW Palatine Hill (Hwy 43-circle-Boones Ferry) 4/27/21
NW Cornell (Westover-Miller) 4/28/21
NW Miller (Cornell-cty line) 4/28/21
W Burnside (NW 25th-Barnes) 4/28/21
bold indicates spray treatments in the last 2 weeks  


Current Phase (in bold)

Description of Garlic Mustard In Each Phase



Like many plants, garlic mustard changes form several times over its lifetime. A typical garlic mustard plant forms as a seedling in the spring and overwinters as a rosette: a low-growing cluster of leaves typically one to six inches tall. The rosette form is easily confused with several native species, and is often hard to find under winter's leaf litter.




With longer, warmer days in March and April, garlic mustard rosettes undergo a change called bolting. The stems lengthen and leaves go from round to triangular.  Buds form at the top of the rising cluster of leaves.




After enough warm, light days in April or May, the bolting plants will open into garlic mustard's characteristic four-petaled white flowers. The flowering stage of garlic mustard typically lasts 2-3 weeks. Herbicide treatment is most effective during this phase. Roots not removed during pulling will likely form a new flowering plant in a few weeks.


Seeds Forming


After all the flowers are gone, the seedpods need 1-2 weeks to "fill in," typically by late May or early June in the Portland area. Careful herbicide treatment can halt seed growth in this phase. Pulling efforts should still attempt to remove all roots. All pulled plants should be bagged and put in the trash to prevent spread in yard debris.


Seeds Ripening


Mature seeds ripen for four to six weeks until the plants begin to dry out, typically in early to mid-July. Pulling can be done in this phase, without regard for root re-growth, but MUST stop when plants begin drying. Herbicide treatment will have no effect during this phase and should not be attempted.


Seeds Ripe Don't pull!


Newly-dry seedpods will explode at the slightest touch, depositing seeds in clothes and hair and making the well-meaning puller an ideal vector for infesting new areas.