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Garlic Mustard

No—It's not something you put on your sandwich

Garlic and mustard, mmm sounds good doesn't it? But, when it's the alien invader, garlic mustard, it spells trouble for our native plants.

Alias (scientific name in latin): Alliaria petiolata

Homeland: This invader comes from Europe and was probably brought here by early European settlers to use in cooking and because some people thought it had value as a medicine.

Invaded Territory: You'll find most of the garlic mustard in the southeastern and northeastern counties of Wisconsin. But, records show it occurring in most of the state.

Garlic mustard grows in upland and floodplain forests, savannas, yards, and along roadsides. It likes to have some shade, so you don't usually find it in open, sunny spots. The invasion of forests usually begins along the wood's edge, and progresses along streams, campgrounds and trails.

How to Identify

This plant grows from 12-48 inches tall. (How many feet is that?) The leaves and stems smell like onion or garlic when crushed (especially in the spring and early summer). This is one way you can tell this plant from other native woodland mustard plants.

This plant is a biennial. This means that it normally takes two growing seasons for it to complete its life cycle. The first year, it has 3 or 4 round, scallop-edged leaves that rise about 2-4 inches above the ground in a rosette. The second year it produces one or two flowering stems with lots of white flowers that have four separate petals. Garlic mustard is the only plant of this height with white flowers in our woods in May. The fruits are slender capsules 1-2 ½ inches long. If you open one of the capsules, you'll find a single row of black seeds with ridged seed coats. It produces hundreds of seeds per plant. Seeds can last for five years.

Method of Travel

It is believed that the seeds hitch rides on the fur of animals like deer, horses, and squirrels. Eventually, they drop off and start new colonies of garlic mustard. People and flowing water can also help this invader spread. The seeds are dormant (they don't grow) for 20 months. Seeds germinate (begin to grow) in early April. The plant flowers from May through early June. Fruits begin to ripen in mid-July and are spread through August.

Garlic mustard is a rapidly spreading woodland weed. Once it gets going it takes over the plants on the forest floor and can take the place of most native wildflower plants within 10 years.

Take control of this alien

For small groups of mustard plants, you can control them by hand pulling at or just before they flower or by cutting the flower stalk as close to the ground as possible just as flowering begins. This keeps the plant from producing seed, and kills the plant itself. If you cut before this, the plant can re-sprout. If you pull by hand, the upper half of the root must be removed in order to stop buds at the root crown from sending up new flower stalks. Cutting is less destructive to neighboring plants than pulling, but you have to time it just right.

For large invasions, managers sometimes burn an area in the early spring or in the fall. But it can take 3-5 years of burning to get rid of the plants and even then, you have to keep your eyes open for small patches that sprout from leftover seed.

Learn more about invasive species from the Wisconsin Department of Natural Resources staff.