It most often grows in the forest understory or along forest edges but is also able to invade undisturbed forest habitats. It tolerates low light levels and is adapted to take advantage of disturbed habitats such as trails, roadsides and areas where trees have been removed.
Garlic mustard has no significant natural enemies in North America, although a diverse community of herbivores feed on it in its native range in Europe. Populations of garlic mustard can spread rapidly. In a study of high quality woodlots, i. When established, garlic mustard becomes a permanent member of the community, often dominating the ground layer habitat over extensive areas. Garlic mustard reproduces only by seed. Most seeds germinate within the first or second year after being produced but can remain viable in the soil seed bank for up to 10 years.
Seeds require prolonged exposure to cold before they can germinate. Seeds germinate in the spring and form low growing rosettes of dark purple to green, kidney-shaped leaves with scalloped edges. Leaves grow on stalks that are a half to 2 inches long called petioles. Young leaves smell distinctly of garlic or onion when crushed, although the odor becomes less intense as plants grow older. Seedling density in infested areas can reach nearly 17, per square yard in the fall, although overwintering mortality is high and rosette density in the spring averages 25 to 70 per square yard, but occasionally reaches as high as per square yard.
Leaves on second year plants are roughly triangular and sharply toothed, a little over one to three inches wide and long becoming gradually smaller towards the top of the stem. As with first year plants, young leaves smell distinctly of garlic or onion when crushed, although the odor becomes less intense as plants grow older.
Shoot elongation from the rosette occurs in the spring, with the plant growing as rapidly as three-quarters of an inch per day. Flowers are continuously produced at the top of the long stalk. Flowering occurs in late April through June in southern Michigan. Flowers are white with four petals that form a cross. The flower is similar to others in the mustard family with six stamens: two long and four short. Petals taper sharply toward the base of the flower.
Individual plants produce from to 7, seeds and grow to 3 to 4 feet in height. Seeds are produced inside slender pods called siliques. Siliques grow on short, rugged stalks and radiate out from the stem.
If you live in an area where free control is not offered, control options follow. All control measures will have to occur annually until the seed from previous years is exhausted. Until you can easily identify the rosette stage of the plant, control is most practical when plants are in bloom. Hand pulling or spraying are the best control options. Hand removal is only successful in small patches that can be visited often and re-pulled frequently. Mowing is not an effective control because plants will still bolt and seed.
To prevent spreading, do not mow garlic mustard when seed pods are present May-September. Herbicides can be used for large infestations, but should be used very cautiously to avoid damage to desirable native vegetation. Spray applications that kill the native vegetation in areas where garlic mustard has gone to seed in prior years will only result in less competition for the garlic mustard that germinates the following year. Herbicide will not kill garlic mustard seed.
Herbicide treatments should be made to garlic mustard plants as they are bolting or are in early flower stage typically early April through late May. Herbicide applications should always be followed up with hand pulling a few weeks after spraying to remove all plants that were missed by the spray or grew after spraying occurred. These plants will need to be bagged and disposed of in the trash. Always monitor sprayed sites and pull any new plants that you find.
If you choose to use herbicides, always read the entire label and carefully follow the instructions. Adhere to the label requirements for application, mixing, and loading setbacks from wells, perennial and intermittent streams and rivers, and other water bodies. Always wear appropriate protective clothing and gear. If you think you have found this plant, please report it immediately. This plant is on our EDRR list , and we provide free control in select areas. If you use an herbicide, spray early in spring or late in fall, because our native plants are dormant at these times, but garlic mustard is still green and vulnerable to sprays.
Glyphosate is a nonselective herbicide, so avoid spraying nontarget plants. Read and follow all label directions on the herbicide product. Encourage your community to scout for garlic mustard in your area and remove it, if found. Ask Your Gardening Question. We teach, learn, lead and serve, connecting people with the University of Wisconsin, and engaging with them in transforming lives and communities. Connect with your County Extension Office ». Find an Extension employee in our staff directory ».
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