Garlic mustard is a known aggressive plant newly introduced to Oregon and expected to become widespread if no action is taken. Introduced to the East coast from Europe, this plant now carpets forest understories of the Northeast and Midwest and continues to spread westward across the United States. In Oregon, garlic mustard is established in the Portland and The Columbia Gorge and a new population was recently found in the Rogue River valley.
As one of the few invasive plants capable of dominating undisturbed forests understories, garlic mustard has the potential to alter forest communities. It can change the tree composition of the forest by suppressing hardwoods such as maples and ashes. An abundance of garlic mustard can alter the suitability of habitats for native birds, mammals, and amphibians.
Garlic mustard is a biennial that can be either self-pollinated or cross-pollinated. Each plant can produce hundreds of seeds, which germinate after a period of dormancy in late February or early March until May. The seeds are believed to be primarily dispersed by human activity, but are also spread by flowing water, birds, and rodents, and may possibly even catch a ride on the fur of larger animals, such as deer.
Since Garlic Mustard has no known natural enemies, is self-fertile, and difficult to eliminate, the most effective control method is to prevent its initial establishment. Burning, herbicides, or cutting are often used to control large existing populations and biocontrol methods are being developed.
Nuzzo, Victoria, Natural Area Consultants. “Element Stewardship Abstract for Allaria petiolata (Allaria officinalis) Garlic Mustard.” The Nature Conservancy
Stinson KA, Campbell SA, Powell JR, Wolfe BE, Callaway RM, et al. (2006) Invasive plant suppresses the growth of native tree seedlings by disrupting belowground mutualisms. PLoS Biol 4(5): e140. DOI: 10.1371/journal.pbio.0040140