What is garlic mustard?

Garlic mustard identification starts with your nose: crush a leaf and it smells like garlic. It’s a biennial in the mustard family from Europe and Asia, likely brought over as a cooking herb, and it has spread through woods, stream valleys and shady yards across Pennsylvania.

The Pennsylvania Department of Agriculture lists it as a Class B noxious weed. It forms dense carpets under trees that crowd out spring wildflowers and tree seedlings, and because it greens up so early, it gets a head start on almost everything else in the woods.

Garlic mustard identification by season

Garlic mustard takes two years to complete its life cycle, and it looks different each year.

• Year one (rosette): a low clump, usually under 8 inches, of rounded, kidney-shaped leaves with scalloped edges. These rosettes stay green through the winter, which makes them easy to spot in November or March when little else is green.
• Year two (flowering): in early spring the plant sends up one or more stems 1 to 3 feet tall. Stem leaves are more triangular or heart-shaped, with coarse teeth.
• Flowers: small, white and four-petaled, clustered at the top of the stem, from about April into June.
• Seed pods: thin, upright pods 1 to 2.5 inches long follow the flowers. By midsummer they dry out and split, scattering small black seeds. Then the plant dies.
• Root: a thin white taproot, often with a distinctive S-shaped kink right below the leaves.

Where it grows in Pennsylvania

Garlic mustard does best in moist, rich soil in partial to full shade. You’ll find it along wooded lot lines, in floodplains and river valleys, along shaded roadsides and trails, and under trees in backyards. It handles a wide range of soils and tends to move from disturbed edges deeper into the woods.

In landscapes, it often shows up in shady beds, along fences and at the edge of the lawn where it meets the woods. Seeds travel on boots, tires, mowers and in moved soil or mulch.

Garlic mustard look-alikes

• Wild violets have similar rounded, scalloped leaves, but they have no garlic smell and bloom with five-petaled purple or white flowers.
• Cut-leaf toothwort, a native woodland wildflower, also has white four-petaled flowers in spring. Its leaves are split into narrow leaflets and don’t smell like garlic. Leave this one alone.
• Creeping Charlie creeps along the ground with square stems, round scalloped leaves and a minty smell, and its flowers are small and purple.

How to get rid of garlic mustard

Hand-pulling works very well for small to medium patches, and it’s the method most homeowners should start with. Garlic mustard has a taproot and doesn’t regrow from root fragments, so a slow, steady pull from the base, ideally when the soil is damp, usually gets it all.

• Pull in early spring, before flowers turn into pods.
• Once flowering stems are up, bag the plants and put them in the trash. Pulled plants can still ripen seed, even from green pods.
• Don’t compost flowering or seeding plants.
• Go back every couple of weeks during spring, because plants bolt at different times.

Cultural: keep shady beds mulched, and fill bare ground with dense groundcovers, shrubs or native plants so seedlings have less room. Avoid moving soil or mulch from infested areas, and brush off boots and equipment after working in a patch. Mowing or cutting flowering stems close to the ground before seed set can help on larger areas, but plants may send up new flower stalks.

Herbicides: for large infestations, Penn State Extension notes that rosettes can be spot-sprayed with glyphosate or with selective broadleaf products such as triclopyr combined with 2,4-D. Late fall and early spring are good windows, since many native plants are dormant and garlic mustard is still green. Glyphosate kills any plant it contacts, so be careful around desirable plants. Read and follow the product label every time; the label is the law. Check that the product is labeled for your site, whether that’s a lawn, a landscape bed, woods or ground near water, where only aquatic-labeled products belong. Applying herbicide for hire in Pennsylvania requires a PA Department of Agriculture pesticide applicator certification, so bigger jobs belong with a licensed vegetation-management company.

Keeping it from coming back

Garlic mustard seed can stay viable in the soil for five years or more, so the job isn’t over after one spring. Expect fewer plants each year if you keep any from going to seed, and walk the area every spring for several years.

Work from the cleanest areas toward the worst ones so you don’t track seed into new ground. If a wooded edge is choked with garlic mustard and invasive shrubs like multiflora rose, clearing the brush and replanting can give you a fresh start.

Questions we get about garlic mustard

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