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. Dark green basal rosettes of scalloped leaves are followed by tall stems topped by tiny white flowers. Crushed young leaves have a distinctively garlic or oniony smell. First introduced from Europe as a culinary and medicinal herb, garlic mustard quickly spreads, 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.
|Common Name||Garlic mustard, garlic root, sauce-alone, jack-by-the-hedge, mustard-root|
|Botanical Name||Alliaria petiolata|
|Plant Type||Herbaceous, biennial|
|Mature Size||1–4 ft. tall, 6–18 in. wide|
|Soil Type||Sandy, loamy, moist|
|Hardiness Zones||4–8 (USDA)|
Garlic Mustard Invasiveness
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 as 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.
What Does Garlic Mustard Look Like
If you have garlic mustard in your yard, not only knowing what it looks like but also being familiar with the plant’s life cycle is important for effective garlic mustard control.
Garlic mustard begins its growth cycle in very early spring. In the first year, low-growing green or purple rosettes appear. The leaves are shaped like a kidney and have scalloped edges. 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.
In the early to mid spring of the second year, the plant develops a (usually unbranched) flower stalk from 12 to 48 inches tall, topped with a cluster of white flowers with four small white petals that are arranged symmetrically. By June, the flowers have died and the plant goes to seed.
How to Get Rid of 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.
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.
How to Prevent Garlic Mustard from Spreading
Do 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.
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.
Can you spray garlic mustard?
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 when the seeds in the soil germinate.
Does garlic mustard grow year-round?
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 choke out early spring plants that haven't had a chance to establish yet.
How did garlic mustard come to America?
The plant is native to Europe and was brought to the United States in the mid-19th century as a culinary and medicinal herb.