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Help save native ecosystems — eat invasive plants

Master Gardener
This is what the rosettes of first-season garlic mustard look like. Submitted Photo

When Europeans came to the lands that now form the United States, they brought familiar plants from home for food and medicine. One of those plants was garlic mustard (Alliaria petiolata), a source of early spring greens.

In its native habitat in Eurasia, it has natural predators that keep its aggressive growth habits in check. Garlic mustard is considered a threat to native forests and has been declared an invasive weed by the Pennsylvania Department of Conservation and Natural Resources. It is found throughout Pennsylvania.

According to records, garlic mustard first escaped cultivation in 1868 on Long Island, N.Y. Since then, it has gone on to out-compete native plants in forest understories and edges from the Atlantic to the Pacific. North American insects and butterflies cannot live on it, and even deer won’t eat it.

Two butterflies, the West Virginia white (Pieris virginiana) and the mustard white (P. oleracea), are threatened because of the spread of garlic mustard. These two butterflies evolved to use native toothworts (Cardamine spp.) as host plants; however, garlic mustard has crowded out toothworts, resulting in a loss of essential food for the butterflies’ caterpillars. If the butterflies lay eggs on the garlic mustard, the resulting caterpillars either do not survive or do not grow properly.

Garlic mustard is a cool-season biennial. Seeds can germinate any time from spring through summer; however, they generally begin to germinate in March before other native plants begin to grow. The emerging garlic mustard plants shade out other plants. It is allelopathic, meaning it produces chemicals that inhibit the germination and growth of other plants, including native plants and tree seedlings. Once germination occurs, it spends its first growing season forming a large rosette of leaves and overwinters in that form.

Second-season garlic mustard has white flowers that bloom in May. Submitted Photo

During its second season, the plant develops a stem with white flower clusters on the tips by May.

As the flowers fade, seeds develop in long, narrow pods. The seed pods mature by June or July, dry out and burst, spreading tiny seeds up to several feet from the parent plant. The second-year garlic mustard plant then dies.

A healthy mature garlic mustard plant can release as many as 800 seeds, which are viable in the soil for up to five years. The high potential reproductive capability of each plant and the fact that seeds germinate all season long and are carried by wind, water, animals and humans are the characteristics that make garlic mustard successful at invading native habitats.

Penn State Master Gardeners of Butler County, working at the Butterfly Trail at Moraine State Park, wage a continuous battle with garlic mustard. Garlic mustard is ubiquitous at the park, but the Master Gardeners attempt to keep it under control within the confines of the Butterfly Trail.

The prime objective of garlic mustard control is to keep the seeds from forming, spreading and germinating. One method has been to hand pull all plants in an identified area. The plants are easy to pull in the spring and root remnants left in the ground do not re-grow.

Another method has been to focus on stopping seed formation by cutting or pulling second-year plants, the ones that are in flower. Since the plants are biennials, they will die in the second year, whether they are able to set seed or not. It is important to bag and dispose of any flowering plant; they can develop seeds if left lying on the soil. This method requires successive cutting of existing colonies.

While you’re working to eradicate garlic mustard, if you’re an adventurous cook, consider its culinary properties.

The entire plant is edible. Roots can be cleaned and chopped to add a mild horseradish flavor to foods. Chopped stems and leaves add a spicy, garlic-like flavor to salads, stir-fries and soup. The leaves and stems of first-year plants are more tender than those of second-year plants, which turn their energy to seed production. To be on the safe side, when using garlic mustard as food, make sure you bag any unused parts and dispose of them in the trash.

If you decide to try eating garlic mustard, make sure to follow safe collection procedures.

Most importantly, do make sure to correctly identify the plant. Ask for permission to collect garlic mustard from private property not your own. Do check the collection site carefully. If you find evidence of runoff from gas, oil and road salts, the plant may be contaminated. Similarly, nearby use of fertilizer indicates possibly contaminated plants.

Penn State Extension offers additional resources on identifying and controlling garlic mustard at extension.psu.edu/garlic-mustard and extension.psu.edu/garlic-mustard-a-ubiquitous-invasive-weed. If you have questions about garlic mustard and other invasive plants, call the Penn State Extension Master Gardeners of Butler County at their Garden Hotline at 724-287-4761, ext. 7, or email the Master Gardeners at butlermg@psu.edu.

Susan Struthers is a Penn State Extension Master Gardener of Butler County.

Susan Struthers

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