Weed of the Month- September

Garlic Mustard (Alliaria petiolata)

(Provided by Master Gardener Peter Russell)

Native Origin: Introduced biennial from Europe, Invasive

Lifecycle: Garlic mustard is a biennial (two-year lifecycle), herbaceous plant that spreads rapidly by seed in many types of woodlands. One of the most invasive and difficult-to-control weeds in the region, it is a major threat to desirable woodland wildflowers, tree seedlings, and wildlife. A single Garlic Mustard plant is capable of producing up to 8,000 seeds in a season.

 Leaf Rosettes

Leaf Rosettes

Habitat: Garlic Mustard is a conspicuous understory plant. It is also found near disturbed areas such as trails, hedgerows, shaded roadsides, and forest edges. First-year plants form low rosettes of 4-8 leaves at ground level. Second-year flowering plants are erect, often multiple-stemmed, from a few inches to 4 feet tall.

Leaves: First-year rosettes have dark green, kidney-shaped leaves with scalloped margins and deep veins. In the second spring, a flower stalk rises from the rosette, having alternate, coarsely toothed, triangular leaves. Crushed leaves smell like garlic, especially in spring.

 Upper Leaves and Flowers

Upper Leaves and Flowers

Flowers. Clusters of small, white, 4-petaled flowers occur only on second-year plants, which can blossom from late April through June. Flowers appear at the top of stalks.

Fruit: Each flower develops into a slender, straight seedpod called a silique. (1"–2.5"  long). Pods are green at first, but turn tan as seeds ripen. Seed dispersion occurs in mid- to late summer. A single plant can produce as many as 3,000 seeds.

Control and Management: Pulling or digging first-year, non-flowering rosettes can be inefficient because many first-year plants will die naturally and because it is difficult to remove the entire root without digging. However, plants uprooted in the rosette stage have no chance of flowering and hence do not need to be removed from the area.
Hand-pulling or digging flowering, second-year plants can be effective for small infestations but is usually not practical in large or established patches. Plants can be pulled anytime during flowering and up until when seed pods are ready to shatter.
Cutting second-year plants close to the ground by hand or with a string trimmer may be effective. For best results, cut just as flowering begins.
After pulling or cutting, it is best to bag and remove all flowering plants. Garlic Mustard should not be composted, because seeds are likely to remain viable. Bagged plants can be landfilled.

Uses: Garlic mustard is a tasty, and nutritious vegetable! The first year rosettes can be foraged year-round, and are said to taste somewhat bitter. The root is also available year-round, and has a horseradish taste. The stems of the second-year plant can be eaten in early to mid-spring, or prior to flowering. These can be used in the same way as asparagus. Later in the year, the leaves of the flowering plants can also be consumed. It is recommended to forage from shadier areas- unless you prefer a more bitter taste. Some recipes using this versatile plant include pesto, salads, and just using it as a pot-herb on its own. 

References:
PCA Alien Plant Working Group
Forest Invasive Plant Working Group
Penn State University, Species Page 2001
The Foreaged Foodie