Garlic Mustard in Corn Hill

~ By Susan Jacobs

On a walk through Corn Hill these days you’ll find a newcomer, GARLIC MUSTARD, among gardens and along walkways. On the Riverwalk you’ll see it just about everywhere. 

Here’s some useful info about it and its importance in our community.

What is Garlic Mustard? 

Garlic mustard (Alliaria petiolata) is a very invasive weed. This European woodland plant introduced to North America by early settlers, thrives in our environment because European insects and diseases that control the plant’s population there are not present here.

What does Garlic Mustard look like?  

Garlic mustard is a biennial plant with a two-year life cycle. The first year, it forms a rosette of round, scalloped-margined leaves that stay semi-evergreen through winter. The second year, it sends up a flower stem with triangular toothed leaves that bears tiny white flowers with four petals. The plant dies after producing long narrow seedpods. At maturity, garlic mustard plants may be 3 to 4 ft. tall and at a minimum bear up to 500 seeds per plant. Crushed stems and leaves of garlic mustard give off a distinct odor of garlic.

Why is Garlic Mustard considered invasive?

Garlic mustard starts growing earlier in the season than our native plants, and outcompetes them. It also produces large quantities of seed. In fact, each plant can produce far more than 500 seeds, vigorous plants may yield 5000 or more seeds which remain viable in the soil for five years or more.

For these reasons, garlic mustard spreads rapidly in wooded areas, forming tall, dense stands (some can be seen along the Riverwalk) that smother native wildflowers, and native tree and shrub seedlings. It can overrun a forest floor in a few years, destroying a previously healthy ecosystem by eliminating many plant species. The roots exude a chemical that inhibits other plants from growing, and it can grow in full sun or full shade, making it a threat to a wide variety of our native plants and habitats. In addition, animals, birds, and insects that depended on a diversity of plant species for food and shelter can then no longer live in the infested area.  

As we prepare for our Butterfly Way Station consider that garlic mustard also produces root exudates that inhibit the growth of important soil fungi and leaf chemicals that kill native butterfly larvae that feed on the plant.

What to do about Garlic Mustard?

  • Manual removal of the plant has been shown to prevent the spread of garlic mustard
  • Best to pull up the plants before they set seed because the action of yanking the plant from the ground will spread the seed.
  • Pulling by hand must remove at least the upper half of the root to prevent a new stalk from forming; this is most easily accomplished in the spring when the soil is soft. 
  • Garlic mustard must be discarded in the trash in a closed container to limit its spread.
  • Hand-pulling should be continued for up to five years in order to deplete any established seed bank. 
  • The hand-pulling method works best in smaller pockets of invasion or in areas recently invaded to help prevent the development of a seed bank.

So if you see GARLIC MUSTARD in the neighborhood, on a good day when soil is moist, before seeds have set, pull it and its root, discard them in a sealed bag in your trash, and you’ll have done your part in limiting its spread in our neighborhood.

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