Seedlings emerge from February to early March and form basal rosettes by the middle of summer. These first-year rosettes are dark green with kidney shaped basal leaves and are very sensitive to drought. Sixty to ninety percent of these first year individuals fail to survive this first summer season. The surviving plants remain green over the winter and then grow very rapidly into the mature, second year form early in the next spring typically early March prior to the leafing of the over-story deciduous trees.
The ability of garlic mustard to over-winter in a green chlorophyll rich form and to survive and grow in the near freezing temperatures of late fall and early spring enables it to take over a system's habitat space and growth resources before the less cold-tolerant plant species can become established. Ecological Impact Garlic mustard is a threat to the forest ecosystems of the midwestern and eastern United States. It is able to form monospecific stands that dominate the understory of even relatively undisturbed forests and actively displace native understory plant species.
Once garlic mustard is established in an area it is almost impossible because of characteristics discussed above to be eliminated. As a permanent component of a site's flora, it increases its presence every year and grows out of control until it completely dominates the site. Tree seedlings especially oaks and many wildflowers including spring beauty, trout lily, wild ginger, bloodroot, Dutchman's breeches, hepatica, toothwort, and trillium cannot survive the explosive growth and spread of garlic mustard.
However, the shallow roots make garlic mustard very easy to remove by pulling it out of the soil. This should be done in the months of April and May before the plants go to seed. Huebner, C.
Olson, and H. Invasive plants field and reference guide: an ecological perspective of plant invaders of forests and woodlands. Newtown Square, PA. Lankau, R. Soil microbial communities alter allelopathic competition between Alliaria petiolata and a native species.
Biological Invasions. Miller, J. Nonnative invasive plant of southern forest: A field guide for identification and control. NatureServe Explorer. Pieris virginiensis - W.
Garlic mustard is also a growing problem in other parts of Washington as well as Oregon and Alaska. Regional collaboration to share information and build partnerships to combat garlic mustard will be the key to stopping this plant in the Pacific Northwest.
If you see garlic mustard in our region outside of King County, please notify the local or state weed board or conservation district office. First identified in Seattle in and listed as a Class A noxious weed in , the King County Noxious Weed Program is working closely with landowners to prevent new infestations and eradicate existing infestations. Without cooperation and vigilance we will lose the battle to keep garlic mustard out of woodland areas throughout western Washington. Garlic mustard seeds typically germinate in fall or early spring and the plant first forms a low, mound of leaves called a rosette that grows from mid-summer through the following spring.
Plants typically bolt and form upright, flowering stems in March and April. Flower buds can be seen on the tops of stems as the plants begin to bolt and then flowers open soon after stem elongates, usually late April through May. Seed production soon follows. Each plant usually produces one flowering stem. However, if a plant is cut or stepped on, many stems will form.
Seeds can form on plants that are cut and left on the ground. Roots crowns will grow new stems if they are not removed completely or if garlic mustard is cut.
Garlic mustard is competitive in a wide range of soils, sun, shade and moisture. It grows in wet soil near creeks and on dry, steep slopes. Garlic mustard's curved root helps the plant hold on to the soil even on steep slopes with loose soil. Garlic mustard has two distinct life stages over its first two years. In the first year, it grows only a cluster of leaves shaped like a rosette, while a strong root system develops.
Plants that survive the winter produce flowers and hundreds of seeds in their second year. Dense stands produce more than 60, seeds per square metre. Stands of garlic mustard can double in size every four years.
Garlic mustard seeds are easily spread by people and animals. They can remain in the soil for up to 30 years and still be able to sprout. The plant can grow in a wide range of sunny and fully shaded habitats, including undisturbed forest, forest edges, riverbanks and roadsides.
Garlic mustard does not provide a valuable food source for native wildlife. Garlic mustard is established in southern and eastern Ontario as far north as Sault Ste. First-year plants produce a rosette of dark green, kidney-shaped leaves. Photo: Leslie J. Mehrhoff, University of Connecticut, Bugwood.
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