4 December 2024
Updates
Spring is a season of anticipation, the first call of the returning Sandhill cranes, the first Hepatica blooms, or the chorus of Spring Peepers at dusk. Another thing that spring brings is the return of invasive species. Garlic mustard is a well-known invasive species that invades our woodlands in the Midwest. With its early spring growth and quick seed production it can quickly invade even diverse woodlands.
Although this species can carpet the floor of woodlands it is one of the easier invasive species to target and eradicate. There are multiple techniques that a landowner or land manager can use on garlic mustard to begin the eradication process. The ultimate goal each season should be to prevent seed production. This is true for any invasive species, but with annual and biennial species it is essential.
Scouting the forest floor in early spring, April and May, allows easy identification of the basal rosettes. These can be hand pulled to prevent the plant from bolting to produce flowers and seeds. Be sure to get the entire root! A follow-up visit to the same area about a month later provides the opportunity to see the species in flower and grabbing any individuals that may have been missed. Priority on these bolting, second year plants, will prevent new seeds from entering the seed bank. Any flowering or plants with seed pods should be disposed of in the landfill in bags labeled as invasive species. You can also allow them to dry and burn them. Do not compost flowering plants or allow them to lie on the ground as they can re-root back into the soil and produce viable seeds.
Using a propane torch to scorch seedlings is another technique that can be used on Garlic Mustard. This is the fastest way to kill hundreds or thousands of future garlic mustard plants in a relatively quick timeframe. Timing is critical as you want the seedlings to only have their cotyledons, first two leaves, exposed or just starting to form their true leaves. Larger plants that are already in the basal rosettes will only be top killed by this technique and will resprout. Be sure to monitor the weather and don’t use the torch on dry, windy days as that may cause any surrounding leaf litter to catch fire.
For large infestations, you can use mechanical or chemical techniques. If there is a large stand of flowering garlic mustard, you can use a mower or string trimmer to cut the plant down. This will prevent new seed from maturing and dispersing into the soil. Basal rosettes can be sprayed foliar in the spring or fall with glyphosate when weather conditions permit. This is not recommended in small populations where there is a high potential for non-targeted damage to be done to surrounding native vegetation. In degraded areas where large populations persist, using cover crop species such as Canada Rye or Virginia Rye. These quick germinating grasses help to shade out the ground preventing sunlight to reach the soil and germination of garlic mustard seeds.
If you are planning to do major restoration in a woodland, such as buckthorn or honeysuckle removal, it is critical to think ahead and plan to monitor the area for garlic mustard following that disturbance. Garlic mustard seeds can be laying dormant in the soil, just waiting for the canopy to open and the sunlight to reach the forest floor. With the removal of the invasive brush, you are likely to find a flush in garlic mustard that will need to be addressed. It can be beneficial to remove sections of buckthorn over multiple seasons to see how the plant community responds. This can allow you to address a small garlic mustard response instead of becoming overwhelmed with yet another invasive species headache.
Having a plan created before starting removal allows you to set achievable goals and use multiple techniques to achieve them. Target small populations first. These will be easier to eradicate and will prevent dense populations from forming or spreading. For isolated populations, marking nearby trees with flagging tape or using marking flags can help guide you back to known populations during follow up visits will make you more efficient on larger parcels. This helps with early spring treatments, especially propane torching, since you know where to look for the tiny germinating garlic mustard seedlings.
Using multiple techniques will allow you to tackle the population at different life stages. This will help to eradicate populations more effectively. As with any invasive plant, early detection is the best way to prevent an infestation. Regularly monitoring your woodland in the spring is a great way to enjoy the Earth waking up from its winter slumber and the many signs of spring’s return and prevent invasive species from establishing.