Wild onions (Allium canadense) and wild garlic (Allium vineale) are persistent perennial weeds that can quickly become a significant nuisance in a manicured lawn. These plants are notoriously difficult to eliminate because of their unique biological defenses and underground structure. They emerge during the cooler seasons, often growing taller than the dormant turf, making them highly visible. Effectively controlling these weeds requires a specific, multi-season strategy that targets their waxy leaves and resilient underground bulbs.
Identifying Wild Onions and Wild Garlic
Distinguishing between wild onion and wild garlic is the first step, although the control methods for both are generally the same. The simplest physical difference lies in the leaves. Wild garlic features leaves that are thin, round, and hollow, often resembling chives. By contrast, the leaves of a wild onion are flat, solid, and not hollow.
Both species possess a thin, waxy cuticle on their leaves, a feature that naturally repels water-based substances, including most general weed killers. This coating is a primary reason why standard herbicides struggle to adhere and penetrate the plant tissue. Furthermore, both plants grow from an underground bulb structure that also produces small, hard-coated bulblets, which serve as a persistent reserve for future growth.
Non-Chemical Removal Techniques
For small infestations, manual removal can be an effective non-chemical option, provided the entire root system is carefully excavated. Simply pulling the plant from the ground is rarely successful because the leaves often snap off, leaving the main bulb and smaller bulblets behind. These underground structures will quickly generate new foliage.
To ensure complete removal, you must loosen the soil around the clump and use a small trowel or spade to dig out the entire bulb cluster. The goal is to remove the primary bulb and all attached bulblets, which can be found several inches deep. This method requires diligence and is best suited for small, isolated patches in loose, moist soil.
Cultural controls, such as consistent and aggressive mowing, can help manage the appearance of the weeds but will not achieve eradication. Regular mowing weakens the plant and prevents it from forming aerial bulblets, which are reproductive structures that allow the weed to spread across the lawn. A dense, healthy turf created through proper fertilization and watering can also naturally crowd out new weed growth, making the few remaining plants less noticeable.
Choosing the Right Chemical Treatment
The waxy coating on the leaves of wild onion and garlic makes them resistant to many common broadleaf herbicides. To achieve systemic control, you must select a post-emergent herbicide specifically designed to overcome this defense mechanism and travel down to the underground bulb. Herbicides containing active ingredients like 2,4-D, dicamba, and mecoprop (MCPP), often sold as “three-way” broadleaf weed killers, are generally effective.
More specialized herbicides containing metsulfuron, sulfentrazone, or imazaquin are also highly recommended for their ability to provide superior control. These chemicals work by disrupting the plant’s growth processes, causing it to draw the poison down into the bulb. For the chemical to work efficiently, it must make contact with the plant’s internal tissue.
To improve herbicide uptake, it is highly beneficial to lightly score or rough up the waxy leaves before application. This can be achieved by mowing the area a day or two before spraying, which opens the leaf tips and allows the chemical to enter more easily. Adding a non-ionic surfactant to the herbicide mixture is also important. The surfactant helps the herbicide droplets spread out and adhere to the slick, vertical foliage, significantly increasing penetration into the plant.
The Importance of Timing and Persistence
The success of any control program relies heavily on timing the application to coincide with the weed’s active growth cycle. Wild onion and garlic are cool-season perennials, meaning they are most active during the fall and spring when temperatures are moderate. The most effective time to apply a systemic broadleaf herbicide is in the fall, typically from late September through November.
During the fall, the plant is actively transferring energy and nutrients from its leaves down to its underground bulb to prepare for winter dormancy. Applying a systemic herbicide at this time allows the chemical to be transported directly to the bulb, effectively poisoning the plant’s energy reserves. A follow-up treatment is necessary in late winter or early spring, generally February to early March, before the plant begins to produce new bulblets.
A single application is rarely enough to eliminate an established infestation due to the presence of multiple dormant bulblets. These bulblets have hard outer shells and germinate at different times, often over multiple seasons. Therefore, a long-term strategy involving repeat applications every fall and spring for two to three consecutive years is often required to exhaust the entire population of underground bulbs and bulblets.