Appendix L
Maintenance Level Guidelines
Garlic mustard (Alliaria petiolata) The leaves of garlic mustard give off a distinctive odor of garlic, and the plant was probably introduced from Europe (where it is a native) by early settlers who were looking for a good source of salad greens. Garlic mustard is a cool-season plant and grows best in moderate to deep shade. It gets an early start in the spring, and makes so much shade that native wildflowers cannot thrive. The first victims of garlic mustard are therefore spring ephemerals such as trillium, bloodroot, Jacob's ladder, and wild geranium. Characteristics Garlic mustard is a biennial plant. Starting from seed, the plant grows in a rosette form close to the ground, gradually spreading. Many of these first-year plants overwinter and as soon as the woods warm up in the spring, they start to grow again. Second-year plants flower in May or early June, forming large numbers of seeds. The seeds are sticky and readily attach themselves to animal fur, shoes, auto tires, etc. The plant is rapidly spread by human activity, as well as by animals. Within a few years, garlic mustard can become dominant on the forest floor, shading out all native plants. Even worse, these seeds can remain alive in the soil for as much as five years. Thus, killing or removing the living garlic mustard plants does not stop the infestation. More plants will arise next year from the plentiful "seed bank." Control The key to garlic mustard control is to attack early, before it has a chance to become widespread. If the woods are already infested, be prepared for a long battle. However, this battle can be won! It just takes time and persistence. Hand pulling Small infestations can be readily controlled by pulling second year plants by hand. The best time to pull plants is when they have just started flowering, but before any seeds have been made. Pulling works best if the soil is moist, such as after a rain. Be sure to pull all the roots out, because roots left in the ground can resprout and form new plants. It is best to put all flowering plants in bags and remove them from the property, because plants that are pulled and laid on the soil may go ahead and set seed. Do not place garlic mustard plants in compost or any other vegetative material, where the seeds might remain alive. Put the bags in a landfill, where they will be immediately buried. Herbicide Large infestations are best controlled by spraying with the herbicide glyphosate, a safe and widely used product. Because garlic mustard begins growth early in the spring, before native flowering plants are growing, spraying at this time should not cause too much if any damage. Glyphosate, available under several formulations from garden stores and agricultural supply companies, should be used at a concentration of 1-2% active ingredient. Read the label to determine the active ingredient concentration and dilute in water accordingly. Spray so that all leaves become wet. A backpack sprayer works best. Glyphosate is quickly inactivated by soil and has no residual effect, so
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Naperville Park District | 2023 MASTER PLAN
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