Tuesday, April 22, 2014

Invasive Plant: Garlic Mustard - Identification & Control

Garlic Mustard should have been on my list of the dirty dozen plants that I try to keep out of my garden.  Here's a quick take on Garlic Mustard, how to identify, and importantly control it. 


Garlic Mustard Background:

Garlic Mustard Invasive - thriving in rock border
Garlic Mustard  (Alliaria petiolata) is an invasive biennial herb with a distinctive garlic/onion smell. First found in New York state in 1868, it was probably brought by Europeans as a medicinal herb. These days it grows in over 31 states and is labeled an invasive plant. It has no natural enemies of note in North America.  Garlic mustard grows in open woodlands, dense shade, driveway cracks, and your vegetable garden.  It's a biennial so in the first year it produces only leaves, the following spring the plant sends out white flowers on ugly stalks up to 3 1/2 feet tall. Each plant can produce 350-7000 seeds which are dispersed in late summer.  





Seeds have a 20 month dormancy period and do not germinate until the second spring after ripening. In addition, it's seeds can last in the soil for at least 10 years. It doesn't need other plants to pollinate - so letting one go to seed in your yard means next year you get many many many more. So you can see how, if established, Garlic mustard can crowd out the plants you really want to grow.
Garlic Mustard - Young Spring Plant
Garlic Mustard seeds are not used by birds and deer / rabbits rarely bother the foliage, possibly because they're repelled by its garlic-like scent.  I'm not sure if goats eat it. There also appears to be few native insects that feed on the foliage and other parts of this plant.
Garlic Mustard - Characteristics & How to identify:
  • Biennial herb that grows to about 3 feet tall, but can be a few inches to several feet tall 
  • Plants are single-stemmed if uncut (mowed)
  • Small, white 4-petal flowers appear in early spring and are in clusters at the top of the stem. In northern Illinois, garlic mustard is the only tall, white-flowered, four-petalled plant that blooms in May.
  • First year the plants are low-growing rosettes with round, kidney-shaped leaves, scalloped on the edges (see photo taken in April 2014)
  • Leaves without any fuzzy or hairy bits
  • Upper leaves on mature plants are smaller, more coarsely toothed and less rounded (maybe even triangular)
  • Plants often smell like garlic, especially when leaves are crushed (smell is gone by fall)
  • Garlic Mustard - Large Tap Root
  • Garlic mustard has a white slender taproot, with a characteristic crook or "s" shape at the top of the root, just below the base of the stem. 
Garlic Mustard - Control Techniques:
There are three techniques for controlling Garlic Mustard - pulling it out by hand, cutting flower heads, and chemical sprays. If you live in an area where you can burn - that should work great! With seeds that last so long - management is a commitment!  I have placed lots of wood chips into the woodlands, and very deep in places. I hope that this has helped control the Garlic Mustard - as the heat may have impacted the seeds (I pray that's the case)  If you can pull out the young plants - that works well. If you don't get the full tap root, the plant will likely return. See the photo - it's a large tap root with a bit of a kink in it, so it can be hard to get out. 

Never let them go to seed - always cut any flower heads you see in addition to pulling the plants. I place the flowers into recycle bags rather than into my mulch. 

Another option to control Garlic Mustard is to actually use it as an herb - while the typical animals in my garden, like deer and rabbit, don't eat it, people do. The young leaves are edible and nutritious – they can be added to salads or boiled and seasoned like spinach.  I hear it makes a great pesto and its roots can be substituted for horseradish
Keep this Hollyhock! 
To add to my challenge this year - keeping this invasive in check. Last year I seed-bombed part of the edge of the woodlands with a large variety of old seeds including Hollyhocks. I really like the look of flowering hollyhocks - although I'd never had much luck with them year after year. The deer seem to like them. Well, I believe they are coming up already this spring. Yeah. However, little did I realize that the leaves for the hollyhock looks very much like Garlic Mustard - take a look at the photo on the right. These two plants are so similar at this stage of growth! I'll have to look very closely when weeding.   

Happy Gardening;

Teresa Marie