Springtime is a time of hope and optimism. As the weather breaks and temperatures rise, people like to spend time outside. And all of that “indoor time” from the previous months contribute to a little “springtime optimism” that creates lists full of gardening and yard projects for the ambitious homeowner.

But you’ll rarely find “fighting with Garlic Mustard” on anyone’s list.

That’s because Garlic Mustard, a fast-spreading and highly invasive weed, can overwhelm you with its ability to grow just about anywhere, the path of destruction it leaves in its wake and its tenacity (some call it down-right stubbornness) when it comes to removal.

What You Should Know About Garlic Mustard

Garlic Mustard can grow in most soil types and can grow in full sun or full shade. It’s an equal-opportunity invader and its roots produce a chemical that is toxic to other plants.

Mowing Garlic Mustard doesn’t control it. The plants will bolt and seed. Many homeowners resort to hand-pulling the plants when they are in bloom and easy to identify (during April), but must revisit pulled sites frequently to make sure more Garlic Mustard hasn’t popped up to replace their lost comrades.

Left unattended, Garlic Mustard can spread quickly. Each plant can produce up to 5,000 seeds which can remain viable in the soil for up to 5 years.

How to Identify Garlic Mustard

(From the East Multnomah Soil & Water Conservation District Website

Garlic mustard (Alliaria petiolata) is a biennial, meaning each plant lives its life over two growing seasons. Seedlings emerge in early March, forming a rosette of leaves the first year. The leaves are alternate, triangular to heart shaped, have scalloped edges and give off an odor of garlic when crushed. The odor can be used to distinguish garlic mustard from native plants like evergreen violet (Viola sempervirens), piggy-back plant (Tolmiea menziesii), fringecup (Tellima grandiflora) and non-native plants such as silver dollar plant (Lunaria annua).

Garlic mustard also has a distinct “s” shaped curve at the base of the stem. Garlic mustard flowers during the second year of growth. In March and April of the second year, plants send up a flower stalk from 12 to 48 inches tall, topped with a cluster of white four-petaled flowers. The seeds form in narrow, green seed pods that originate from the center of the flowers and turn brown as the seed matures. The plant dies after producing seed and the brown, dried out stem with the brown seed pods remain through winter.

How to Control Garlic Mustard

Hand pulling and herbicides are the two most effective methods of controlling Garlic Mustard. While hand removal may work for small patches that can be re-visited frequently, herbicides are often used for large infestations. Over-use of herbicides that manage to kill off other native vegetation that may compete with Garlic Mustard only results in less competition for the Garlic Mustard seeds that germinate the following year.

Herbicides don’t kill Garlic Mustard seeds.

The video below provides more instructions on how to deal with Garlic Mustard:

What is Riverdale Doing About Garlic Mustard?

Riverdale is currently conducting an audit of the invasive species in the City-owned woods, trails and other greenspaces. We have also been asked by Arconic to audit their property as well since so much of it lies next to Riverdale’s. Scott Community College is conducting a similar audit.

We all know the audits will report a significant population of Garlic Mustard within the City’s geography – but the audits will help us identify the areas where widespread treatment is called for. In subsequent years, the City expects to spend a significant amount of money to gain control and then manage the Garlic Mustard spread in the City. 

Residents are encouraged to inspect their own yards and the wooded areas around their homes to identify patches of Garlic Mustard. If possible, we ask residents to pull and manage what patches they can and to let City Hall know if there are patches that are just too big for them to handle on their own.

By working together, the City, its residents and local business and education concerns can stem the tide of Garlic Mustard, saving all parties hundreds of thousands of dollars in habitat replacement, unnecessary erosion damage and worse. 

Thanks for your help.