arlic mustard is a pervasive weed problem throughout most of the Northern US. This invader is a cool weather biennial native to Europe that immigrants brought with them for an early season edible green and medicinal herb. It has since flourished, taking over understory ground cover in forests and disturbed sites. According to ODA, this weed is in limited distribution in Hood River, Clackamas, Columbia, Polk and Tillamook counties and abundant in Multnomah County. Unfortunately, its spread in Yamhill County seems inevitable.
This weed is an early bloomer and usually begins flowering in April and May. The plant has a 2 year life cycle with a first year rosette stage and a second year flowering stage. It can thrive in both sun and shade and is usually found in disturbed understory forest habitats. Garlic mustard only spreads through seed distribution and seed viability is estimated to last around 5-7 years. It has allelopathic traits, poisoning the soil around it, which depresses growth of surrounding competition. In fact, it has been estimated that Garlic Mustard patches can grow in size about 20 ft a year. First year rosettes are usually low to the ground with 3-4 kidney shaped, scallop edged leaves that resemble the native fringecup. In its second year it can grow to be 1-4 ft tall in maturity with little white flowers with 4 separate petals that form a distinct cross. True to its name, its leaves and stems smell like garlic when crushed.
Garlic mustard can be hand pulled if seen, but should be disposed of in bags because seeds can continue to ripen after plants are pulled. Any root fragments left behind will most likely resprout, which means sites will need to be monitored after weeds have been pulled. Mowing is NOT an effective control of Garlic Mustard because this will encourage the plant to bolt and may lead to additional seed head creation. This is especially true after seeds are present (May – September) and will actually lead to greater infestations. Chemical application is encouraged in April or May when the plant is bolting or beginning to flower which can be problematic if there is wet spring weather.
If spotted in Yamhill County, we urge you to report it immediately to the Invasive Species Hotline (1-866-INVADER). Early detection and rpaid response is critical in limiting this weeds spread into Yamhill county. Please also be aware this summer, especially if you are returning from areas such as Portland or the Columbia River Gorge hiking trails, that this plant is spread by seed. Use trail head boot brushes if they are provided. Please help us keep Yamhill County free of Garlic Mustard!
Garlic Mustard in the first year rosette stage
- Garlic Mustard second year flowers