The definition of a weed is not always clear-cut. Many naturalized plants, such as Queen Anne’s lace, are viewed as a nuisance by some and as a delight by others. For garlic mustard, however, the conclusion is unanimous: It is a highly invasive plant that should be controlled by all means.
First introduced from Europe in the mid-19th century as a culinary and medicinal herb, garlic mustard quickly spread all across the United States, crowding out native plant species and, in the process, endangering insect diversity. At many locations in the United States, garlic mustard has become such as problem that some weed control boards actually require property owners to eradicate it.
If you have garlic mustard in your yard, knowing the plant’s life cycle is important for effective garlic mustard control. Though rarely purposefully planted, it begins its growth cycle in very early spring—in the first year, low-growing green or purple rosettes appear, from which 8-inch long, hairy stems will emerge, bear seeds, and eventually multiply. In the spring, it's relatively easy to identify garlic mustard by the strong pungent garlic or onion smell of the new leaves, but the odor dissipates as the season progresses.
|Botanical Name||Alliaria petiolata|
|Common Name||Garlic mustard, garlic root, sauce-alone, jack-by-the-hedge, mustard-root|
|Mature Size||1–4 ft. tall, 6–18 in. wide|
|Sun Exposure||Sun exposure|
|Soil Type||Moist, sandy, loamy|
|Soil pH||Neutral to acidic|
|Hardiness Zones||6–8 (USDA)|
Garlic Mustard Care
What makes garlic mustard so invasive is that a single plant produces between 600 and 7,500 seeds, which can survive in the soil for up to five years. Even more discouraging, garlic mustard is also allelopathic, which means the plant releases chemicals into the soil that inhibit the growth of other plant species. If not controlled, garlic mustard will grow into large monocultures, the types that you might see in wooded areas while hiking.
Garlic mustard also affects insects, including butterflies, as it chokes out native host plants such trillium, hepatica, Dutchman's breeches, bloodroot, and wild ginger. These native plants provide important pollinators and insects with egg-laying sites and food sources. Additionally, the chemicals in the leaves of garlic mustard can even kill the native butterflies that feed on them.
While large swaths of garlic mustard are most frequently found in woodlands, the plant can grow virtually anywhere, in any conditions. Areas of disturbed soil are prime territory for garlic mustard. If you dig up an area of your yard and you’ve had issues with garlic mustard in the past, don’t leave it unplanted—garlic mustard will move in quickly.
Garlic mustard is very adaptable and can thrive under a variety of light conditions, including full sun and full shade. In fact, you may spy the plant growing beneath the canopy of low-lying shrubs or bushes in your lawn.
Garlic mustard will do best (invasively speaking) in soil that has been recently disturbed and moderately moist. That being said, it can thrive in a variety of mixtures, including sandy and loamy soil, and neutral to acidic pH levels.
Garlic mustard loves moisture and will thrive in conditions that are damp or humid. The weed is fairly drought-sensitive, so areas that are experiencing less-than-average rainfall (or an especially dry and hot season) may notice a decreased occurrence in the spread of garlic mustard.
Temperature and Humidity
Unfortunately for many gardeners and homeowners, garlic mustard is capable of thriving under a variety of different environmental temperatures, including highs above 90 degrees Fahrenheit and lows below 32 degrees Fahrenheit. In fact, in many places garlic mustard can remain green and grow throughout the entire winter, allowing it the ability to chock out early spring plants that haven't had a chance to establish yet.
Garlic mustard is an invasive species, and therefore should not be fertilized or encouraged to grow in any way.
Removing Garlic Mustard
If garlic mustard pops up in your yard, you need to make sure that it does not turn into a satellite infestation. As soon as you spot the weeds, remove the plants from the ground, making sure to take the entire root system with them. If the soil is loose and wet, you might be able to hand-pull them but getting the entire taproot out usually requires a garden knife or similar weeding tool.
It's also important to remove second-year, mature garlic mustard with its entire roots before it starts to flower between April and June. If you miss that point in time, you will get another chance during the short time window when the garlic mustard is done flowering and before it sets seed within a few days.
Keep in mind, you should not compost the pulled plants—the seeds can remain viable even in the hot temperatures of your compost bin or pile and regenerate once that compost has been applied to your garden or landscape. It's also a good idea not to leave the pulled plants lying around, as they may continue to develop and set seed. Always dispose of pulled plants in plastic bags. You can also burn them, but you need to do it promptly before they dry because otherwise the seed pods can burst open and disperse the seed. First-year seedlings can also be buried deeply in a location that will remain undisturbed.
Applying an herbicide to counteract your garlic mustard is generally not recommended, as it will kill all other plants nearby. Plus, even with repeated herbicide applications, garlic mustard still comes back. If you are dealing with a large, established infestation of garlic mustard, it will take several years to control it. By removing any emerging seedlings and mature plants before they spread more seeds, you can gradually exhaust the seed bank reserves.