Alien Alert

Garlic Mustard

We’ve had an insurgence of alien plants invade our creek side this spring. I have to attribute this new uprising of Garlic Mustard, Alliaria petiolata, to the unseasonably warm winter we’ve had here in Illinois. I imagine, that given that Garlic mustard appears on the noxious weed list for thirty-seven of the fifty states, I am not alone in my mission contain the beast.

It is important for one to know your enemy. Alien identification is critical to eradication!  Gardeners often confuse first year Garlic mustard plants with Wood Violets and the noxious weed, Creeping Charlie.

Wood Violet by Kylee Baumle

Mature garlic mustard surrounded by Creeping Charlie

Creeping Charlie

A description of the adult and yearling plant follows:

 

 

 

 

  • the adult, flowering plant has alternate, heart or triangular shaped, 1 to 3 inch wide, coarsely toothed leaves, and ranges in height from 12 to 48 inches;
  • it produces one or two stems with numerous white flowers that consist of four separate petals;
  • the petioles are longer on the leaves towards the base;
  • a distinctive onion or garlic odor is emitted from the plant when crushed. The olfactory characteristic of this plant helps to distinguish Garlic mustard from all other woodland mustard plants;
  • its taproot is white, slender and often bent in an S-shape near the top;
  • soon after flowering, 1 to 2.5 inches long seed capsules form, quickly lengthening and maturing to produce more than 100 black seeds per plant; and
  • first year plants have wrinkled kidney shaped, scalloped-edged leaves arranged in a cluster of 3 or 4 round, that form a rosette.

Triangular leaf and white flower

Yearling

A complete plant profile is available on United States Department of Agriculture: Natural Resources Conservation Service  web page.

Garlic mustard has been found throughout the northeastern and Midwestern U.S. from Canada to South Carolina and west to Kansas, North Dakota, and as far as Colorado and Utah. Early settlers introduced the plant from Europe onto a new continent, North America, and specifically, the United States. Garlic mustard was brought to the New World because people believed it had medicinal properties. Some settlers even cooked with this cool-season, biennial herb.

Clearly, this alien has occupied our soils for a long time, giving rise to a particular stronghold in the shade of upland and floodplain forests, savannas, yards, and roadsides. Invasion has usually begun along the forest’s edge, with the troops progressing along streams and trails. Light, moisture, nutrients, soil, and space are monopolized by the aggressive Garlic mustard once it has taken hold in an area. Once established, Garlic mustard, a fierce competitor, releases its secret chemical weapon, glucosinolates, into the soil, preventing other, desirable, native woodland wildflowers and trees from flourishing. Aggressive spread of the plant has lead to domination of the forest floor and native herbaceous species displacement within ten years.

Native woodland flora’s survival and the wildlife that depend on them are threatened by garlic mustard invasion. Garlic mustard is spread in two ways: an advancing plant front and population expansion facilitated by animal, flowing water or inadvertent human seed  dispersion. Once dispersed, seeds remain viable for five years. In the Midwest, garlic mustard seeds germinate in early April. Vegetative plant growth begins early in the spring, and flowering from May through early June. Viable seeds are produced within days of initial flowering. Seeds begin to ripen in mid-July, and are disseminated throughout the month of August.

Description: Garlic Mustard (Alliaria petiolat...

Description: Garlic Mustard (Alliaria petiolata), seeds. The numbers on the scale are centimeters. Date: 2005-08-19 (ISO 8601) Author: Björn Appel, Username Warden Licence: GFDL, CC-BY-SA-2.5 or CC-BY-SA-2.0-DE (at your option) Related: Comment: (Photo credit: Wikipedia)

Understanding of the Garlic mustard’s life cycle is key to effective control strategies. Over time, warfare tactics may vary depending on the extent of the invasion. However, after the initial counter insurgence, eradication procedures must be applied for eight or more years to insure that garlic mustard seed bank has been depleted. Each spring, vulnerable areas such as woodlands should be monitored to ensure prompt detection of new invasions and help to prevent re-occurrence. A gardener’s arsenal against Garlic mustard includes:

  • hand pulling followed by bagging and burning or deep burial of the enemy;
  •  decapitation at a height of two to three inches above the soil’s surface before flowering. Follow-up monitoring is required to insure complete enemy elimination;
  • chemical warfare may be needed for instances of extensive infestation. Land-locked, enemy eradication can be accomplished with spring or fall application of a 1% or 2% glyphosate solution. Killzall (TM) and Aqua Master (TM) are safer chemical weapons for use near water; and
  • finally, controlled burns, may be used in the spring to kill the newly germinated seedlings. Permits and certification are usually required to conduct a burn. Contact your local fire control agency for permitting requirements prior to using this method.

Prairie restoration requires gardener’s to engage in warfare against invasive aliens such as Garlic mustard. The battle can be long and intensive, but territory reclamation is vital to the growth of the forest communities’ native plants and animals. Ethically speaking, this is a just war!

Related articles

Resources

Eberhardt, Laurie and Finger, Jonathan. “Mapping and Testing a Possible Control Method for Garlic Mustard (Alliaria petiolata).” Pierce Cedar Creek Institute,   Ecological Society of America presentation, Aug. 2007.

“Garlic Mustard (Alliaria petiolata).” Invasive Species, Wisconsin Department of Natural Resources, 3 Sept. 2004. Web. 26 Apr. 2012.

Pyle, Charlotte. “Alliaria petiolata (M. Bieb.) Cavara & Grande garlic mustard.” Plants Profile, United States Department of Agriculture: Natural Resource Conservation Services, USDA, Oct. 2002. Web. 26 Apr. 2012.

Wikipedia contributors. “Glucosinolate.” Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 28 Mar. 2012. Web. 30 Apr. 2012.

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3 Comments

  1. This spring I pulled an area of garlic mustard before it went to seed, and left the individual specimens scattered on site to die in the spring sun. This worked because it didnt rain much. Not having to bag and dispose saved alot of time and energy i could devote to pulling. Now it is too late to do this, as they have all started to go to seed. Great article!

    Reply
    • Garlic mustard disposal while time consuming is a necessary evil because its seeds can remain viable for up to seven years!

      Reply
  1. Garlic Mustard, Control Advice From the Front Lines | WingraSprings

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