By Joyce Fisher, Master Gardener, Cornell Cooperative Extension
Spring has come and gone and with it, the weeds have grown by leaps and bounds. The weed that has invaded my property and the neighboring lots is called garlic mustard (Alliaria petiolata).
Garlic mustard is a noxious, invasive weed. It produces chemicals that inhibit the growth of other plants, fungi and butterfly larvae, and crowds out native plants because of its invasive mat-like growth pattern. Just a note: The reason they call it garlic mustard is if you rub the leaf between your fingers it does smell like garlic!
This plant can grow up to 4 feet tall, and it produces one flowering stalk with four-petal, white flowers clustered at the end of the stems in early April–May. Mature leaves are triangular with longer teeth edges, which become smaller at the top of the plant. The rosettes, the young plants, have kidney-shaped leaves (this is what you will see now that it is summer).
If left untended, this weed can completely cover a field, vacant lot or forest floor. It is a non-native biennial herb and spreads by seed; biennial means that it grows from a seed the first year into a rosette stage plant and flowers the following year. Dense shade or sunny sites, this plant is able to grow in almost any condition (if only all our plants were so adaptable)!
You can control this weed; however, your control(s) may require a number of years to be completely successful, and you may find it necessary to combine methods for complete removal. Here are three ways to control this plant:
Manual: Pull “mature plants” in the early spring or cut the flowering stalk to the ground. IMPORTANT — remove the stems and flowers from the site. Do not put in compost or weed pile as seeds can live over the winter and start the cycle all over. Do not try to pull the rosettes, they will break at the roots and allow the plant to re-sprout. A shovel or garden tool that can get down to the roots would work fine.
Mechanical: Tillage may be effective for large areas but may initially expose more seeds for germination. Seeds can remain viable in the soil for up to five years. This is why you will have to be vigilant for a number of years to achieve complete eradication. Take note — plants will flower again after mowing, which stimulates crown growth and side roots. Even if the plant is only in bud, you must remove the plant from the site as they can still form viable seeds.
Chemical: Always follow labels exactly as written and use only herbicides legal for the site you are treating. Herbicides are effective on rosettes. Spraying in the spring or fall with glyphosate is the most effective chemical control. The products containing 2,4-D do not significantly control this weed.
At my home, I am making headway on finally ridding my property of this plant. This is the third year we have been working on it. I use a combination of methods as advised above, hand pulling around flowerbeds and hedges, and chemical application on the abandoned field behind our property. I have also taken on the task of educating our neighbors to this very invasive plant.
For more information go to Cornell’s website: http://counties.cce.cornell.edu/oneida/home%20garden/WEEDS/Garlic%20Mustard.pdf