Invasive Plant Series Part 2

Invasive Plant Species on Glidden Drive, Part 2 
                                     (continuing from article that appeared in the November, 2013 newsletter)
                                                                   John Swanson, GDA Board Member

                                                                         
 Garlic Mustard

Garlic Mustard has been making inroads in Door County. It has definitely been seen along Glidden Drive. This is a species that we should be concerned about and take steps to eradicate it. 

It is recognized as a herbaceous biennial with stems 2-4’ tall. First-year plants form a basal rosette that remains green through the winter. Second-year plants produce one to several flowering stems.

Ecological Threat:

  • Invades high quality upland and floodplain forests (that

    would be us) as well as disturbed areas, such as yards and roadsides. It is sometimes found in full sun, though most often grows in areas with some shade, and does not do well in acidic soils.

  • Native herbaceous cover has been shown to decline at sites invaded by garlic mustard. Whole forests can be taken over by garlic mustard.

  • Garlic mustard exudes antifungal chemicals into the soil that disrupt associations between mycorrhizal fungi and native plants, suppressing native plant growth.

  • Leaves: First year plants have basal leaves that are dark green, heart or kidney-shaped, with scalloped-edges and wrinkled appearance. On second year plants, stem leaves on flowering plants are alternate, triangular, with large teeth, and up to 2-3” across. Leaves and stems smell like garlic when crushed. 

Removal

Pulling or cutting the root from the stem before flowering are effective individual plant control techniques. Pull if soil conditions allow for the removal of the taproot. Pulling second- year plants is easier than pulling first-year rosettes. Alternately, cut the entire taproot with a sharp shovel or spade 1–2” below the surface. If flowers are present, bag material and dispose of it in a landfill to avoid potential for seed spread. Mowing appears to help control but may not eradicate the plant. 

Chemical Removal

Roundup (Glyphosate) applied to rosettes in fall or spring or to flowering plants has a 90-100% in season success, but seedlings may still emerge following spring.

Questions: Email the Door County Invasive Species Team: dcisti@gmail.com or call: 746-5955



Description for Identifying in the Field

Flowers: Small, white, 4-petaled, and abundant. Bloom throughout the spring.

Fruits & seeds: Seed pods are long (1-2 1⁄2)”, slender capsules (siliques) green in color, drying to pale brown. Seeds remain viable in the soil for at least 7 years.


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