Garlic Mustard: A Threat to Skyline's Woodland Habitat

Garlic Mustard
1st Yr. Plant in Rosette Stage in fall-winter
White flowers with 4 petals April-June

What is Garlic Mustard?

Garlic Mustard (Alliaria petiolata) is a noxious weed with economic and
habitat consequences.  It is a member of the exclusive club, Oregon’s Noxious Weed List.  Unlike what its name would suggest, garlic mustard is not a rare culinary herb.  Instead garlic mustard is an aggressive, highly invasive, malevolent plant from Eurasia and has become a major threat to the health of our local woodland habitat.

Why is it a threat? 

•  It out-competes woodland native plants by aggressively monopolizing light, moisture, nutrients, soil and space. 
•  It reduces plant diversity.
•  It decreases essential food sources to wildlife species that depend upon native plants for their foliage, pollen, nectar, fruits and roots.                      
•  It negatively alters soil composition and structure and harmfully impacts soil fungi that are vital to native hardwoods.                 •  It has a high seed production and the ability to spread rapidly.

Where does it grow?

It most often grows in woodland understory or along forest edges.  It is shade tolerant and has adapted to take advantage of areas where the soil is disturbed, such as along animal & people trails and along roadsides.

What are its characteristics?

•      Garlic mustard is a biennial, meaning the plant lives for two years. During its first year, it forms a basal rosette with kidney-shaped  scalloped leaves.  (see photo)
•      In the spring of its second year, it bolts and elongates becoming 12-48 inches tall.  Leaves alternate on the stem, are sharp toothed and triangular in shape.  Flowers are white with four petals growing on a single stalk. 
•      A good nose will smell a garlic-like odor when the plant is crushed.        
•      Seeds grow in long, narrow pods which eventually will burst and disperse the seeds.

How does it spread?

The 2nd year flowering plants produce seed pods (siliques) that burst, releasing thousands of seeds, and dispersing them up to several yards from the parent plant before the plant dies.  Seeds can remain viable in the soil for 5-10 years, consequently, effective management requires a long term commitment.

Shoes, pets, bicycle & vehicle tires can pick up seeds, spreading them to sites uncontaminated by garlic mustard… and to your property!  Clean your boots!  Wash off bike tires.  Brush the dog.  Do not spread seeds.

Places to Inspect Plants & Get Information (April thru June)

•      Plainview Grocery    11800 NW Cornelius Pass Road   (corner of Skyline & Cornelius Pass)
•      Skyline Grange     11275 NW Skyline Boulevard
•      Roadside Display Signs along local roadsides, such as Skyline, Newberry, & Germantown

Need Help with Garlic Mustard on Your Property?

A number of local agencies may be able to assist landowners with garlic mustard.  Some give priority to infestations in riparian areas.  You will need to sign and return a Permit of Entry form before an agency can treat your garlic mustard.  Treatment may involve spot spraying with an herbicide or hand-pulling or both.  Return the form now; treatment period is limited usually to April-May. 

If you live within the City of Portland
•      Download Permission Form from City of Portland’s Bureau of Environment Services at
•      or contact Mitch Bixby at 503-823-2989 or  mitch [dot] bixby [at] portlandoregon [dot] gov

If you live in unincorporated West Multnomah County
•      Download Permission Form from West Multnomah Soil & Water Conservation District at
•      or contact Mary Logalbo at (503) 238-4775 x 103 or  mary [at] wmswcd [dot] org

If you live within the SRN or FPNA boundaries
•      See above information about The Skyline Resident-Based Garlic Mustard Effort.

Web Sources of Information & Photos:


Excellent Online Video

“Stemming the Tide: Garlic Mustard ID & Control” at

Updated March 2010 by Sen Speroff