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Invasive Garlic Mustard, Alliaria petiolata

I have bad news for you: The smell of garlic in your backyard after some weeding is not coming from a new Italian restaurant down the street. The smell is likely coming from the 2-4 foot plants with four-petaled, white flowers nearby. Look closely at the leaves – if they are triangular and sharply-toothed, you found the culprit. You have a patch of invasive garlic mustard.

WHY IT’S BAD:

Garlic mustard is often considered one of the more problematic invasive plant species in our parks and yards. Though this herb takes 2 years to reproduce (biennial), it will take over many of the outdoor spaces where it is introduced.

The first record of garlic mustard in the United States, came out of Long Island, New York in 1868. It was originally introduced for herbal and medicinal purposes. Now, it has taken over large areas in our green spaces.

Laura Fay, from Friends of the Lower Olentangy Watershed, reminds us, “although it may look pleasant to have an area, heavily covered by greenery, the quality of the greenery is of utmost importance for a healthy food chain.” Invasive garlic mustard provides no known benefit to North American wildlife, and can be toxic to certain butterfly species’ caterpillars.

One characteristic that gives garlic mustard a competitive edge is that it secretes chemicals that suppress neighboring plant growth. It also suppresses fungi found in soil that  benefits trees. While they are suppressing other plants, each garlic mustard is also generating thousands of seeds for dispersal. These hardy seeds can remain viable for up to ten years.

Over time, garlic mustard can  dominate  once rich and vital native habitats.  Columbus and Franklin County Metro Parks’ Assistant Resource Manager Carrie Morrow says that the greatest risk to the environment caused by garlic mustard is “decreasing diversity in habitats.”

HOW TO IDENTIFY:

Attribution: Phyzome at the English language Wikipedia
Young garlic mustard. Photo by Phyzome at Wikipedia.
Attribution: Sannse at the English language Wikipedia
Adult garlic mustard. Photo by Sannse at Wikipedia

In summer and fall of its first year, garlic mustard produces a leaf rosette. This small rosette can easily go unnoticed and is often mistaken for violets, which are common, nutritious edible flowers. The following spring, second-year garlic mustard emerges as a 2-4-foot-tall flowering stalk.

HOW TO ELIMINATE:

The best way to eradicate garlic mustard is to remove the plant before it sets seed. Each plant can produce in excess of 7,000 seeds. Fortunately, even if the garlic mustard has matured, smaller populations can be controlled relatively easily… as long as you are willing to put in diligent effort. To control smaller populations of the plant:

 

  1. Pull the plant from the base. Try to get all of the root, as the plant can resprout otherwise.
  2. Bag the plant or otherwise remove it from the premises. Garlic mustard can continue to mature after being pulled. Leaving it on the ground means the seed can still spread.
  3. Repeat this process for two years in a row, or as long as garlic mustard is present.

Larger populations will be harder to tackle, so you may want to cut the stems low in the spring to prevent flowering and seed production. Again, regardless of the tactic, you want to make sure that flowering plants are completely removed from the area.

Carrie Morrow of Metro Parks says they “have found that mechanical pulling before it is in flower is the best method” of control. Morrow does point out that it is difficult to prevent the plant from growing, and reminds people that “its seeds persist for more than 7 years in the soil.” So even if you have removed the plant from an area, monitoring should continue, as it could return.

Most people don’t plant garlic mustard intentionally. If you were thinking about doing so because you like the look or the coverage try these ODNR recommended native alternatives: white baneberry (Actaea pachypoda), columbine (Aquilegia canadensis), blue phlox (Phlox divaricata), and black cohosh (Cimicifuga racemosa).

To learn more about this plant, check out:

http://ohiodnr.gov/invasiveplants

https://www.oipc.info/invasive-plants-of-ohio.html

https://plants.usda.gov/core/profile?symbol=alpe4