Garlic Mustard—Springtime’s Worst Offender

When managing the natural lands, I’ve found it’s almost like a strategy game. Which areas need the most attention right now? Which will need attention in two weeks? In three months? Right now, in spring, I always have a few things on my plate. After mowing the meadows, I usually turn my attention to the woodlands. With our beautiful native spring ephemerals blooming in the woods, it’s a good time to figure out what doesn’t belong.  Without fail, one of my least favorite invasives always rears its head: Garlic Mustard! Garlic Mustard (Alliaria petiolata) is a broadleaf biennial in the mustard family native to Europe and Asia, which has happily made a home here in woodlands, road edges, and shaded floodplains.  It’s easily identifiable from the garlicky smell of the plant, round, slightly toothed leaves, and white, four-petaled (cruciform) flowers that shoot up from the basal rosette in April–May.  While the basal rosette of leaves is present year round, the flower shoot is specific to second year plants, and is present April–June.  The plant can reach up to three feet tall, and the seed pods are slender capsules typical of the mustard family called siliques.

So, why do I have so much dislike for this plant?  Well, it all comes down to ecology.  Garlic Mustard has a mechanism called allelopathy.  Basically, this means that the plant emits a chemical from its roots that disturbs the natural soil chemistry.  This prevents native plants from growing, native seeds from germinating, and encourages more growth of Garlic Mustard.  Slowly, it can decrease the natural diversity of native plants in a wooded ecosystem.  When a monoculture of Garlic Mustard occurs, it can lead to poor soil nutrient cycling and soil health decline, as well as a decline in the diversity of animals and insects that rely on native plants to survive. Fortunately, this nasty plant is most effectively controlled by hand pulling!  For me, this time of year before the plant goes to seed is the ideal time to pull this plant aggressively. I like to pull the plant from the base as close to the soil as I can get, and gently pull it out of the ground. Especially after a rain, it comes right out- roots and all!  A little shake to knock off excess soil, and it’s into the weeding bucket. Be sure to go at a nice steady pace.  Too fast, and you may inadvertently break the plant at the root since the main tap root usually juts sharply to one side. This can lead to re-sprouting later in the season.

At this point in the development of the plant, I can usually compost it without issue. If composting isn’t an option, and I have to leave the plants behind, I’ll take my bunch of pulled plants and prop it up against a tree with the roots in the air so that the plants dry out and die without re-rooting.

If the plant has any seed capsule development at all, I will bag the plant and throw it away.  These seed capsules can still mature and spread seed- even after it’s been pulled!  Because the seeds can persist in the soil for a long time, this is a process I’ve had to repeat in various woodlands throughout the property for a few years.  But every year, I notice the decline in the Garlic Mustard population!  It’s the long game with Garlic Mustard, but one worth the effort. If you’d like to know more about this invasive plant, or other invasive species in Delaware, you can go to the Delaware Invasive Species Council website!