Identifying and Controlling Invasive Weeds

(Question)

Hello! I recently enjoyed a presentation at the library on gardening by one of your volunteers. Can you help me identify this weed and offer advice on how to best control it please? They tend to grow tall and out of control despite my efforts to remove them.

 

(Answer)

The plant in your picture is garlic mustard, considered one of the most problematic and common invasive species in Ontario forests.  It is a biennial, forming rosettes in the first year and tall flowering stalks in the second.  The seeds which form from flowers on the second year plants, can remain dormant in the ground for five or more years.

You can take the following steps to remove this plant from your garden, and to prevent in spreading throughout your neighbourhood:

  • Hand pulling – this control method can be appropriate where there is a relatively small population of garlic mustard. However, it must be done thoroughly, including getting out the root, as the plant can continue to sprout new stems from the root and the accompanying soil disturbance will stimulate germination of garlic mustard seeds in the soil. Hand pulling is more likely to be successful if followed by replanting of native species as some species can successfully out compete garlic mustard.
  • Basal  cutting – which involves cutting the stem at the base on the second year plants, ideally just after the plants flower and before they produce seeds.  As garlic mustard plants flower at different times, you may need to repeat this several times.  This control technique will reduce soil disturbance and may reduce seed germination. Cutting is preferable to hand pulling because it reduces the soil disturbance. Depending on the area where the plants are growing, you may be able to do the basal cutting with a mower.
  • Use of herbicides – in a home garden, under Ontario pesticide rules, you are not able use herbicides to control garlic mustard (there are excepts for agricultural lands and forest management).

Note do not compost any plant material.  It should be put in yard waste bags and ideally left in the sun for at least a week before being disposed of.  This is important because pulled plants which have flowers can still produce seeds.

The Ontario’s Invading Species Awareness Program web site has some excellent information on garlic mustard and other invasive species.  http://www.invadingspecies.com/invaders/plants-terrestrial/garlic-mustard/

Good luck!  It is possible to get rid of this plant, and important to try and do so.