Wild onion (Allium canadense) and wild garlic (Allium vineale) are perennial weeds that commonly frustrate homeowners by emerging in lawns and gardens. Their ability to survive winter and the difficulty of complete removal make them a persistent nuisance. Effective management requires a combined approach targeting both the visible foliage and the reproductive structures hidden beneath the soil. This article provides strategies, from physical removal to chemical treatment and long-term prevention, to eliminate these stubborn alliums.
Understanding Wild Onion and Garlic
Wild onion and wild garlic are winter perennial weeds that thrive during the cooler months, emerging in the fall and growing through the winter and early spring. While visually similar, a quick inspection of the foliage can help differentiate the two: wild garlic leaves are round and hollow, resembling chives, whereas wild onion leaves are flatter and solid. Both plants, however, emit a distinct, pungent aroma when their leaves are crushed or cut, which is a tell-tale sign of their presence.
The primary reason these weeds are challenging to eradicate lies in their complex life cycle and reliance on underground bulbs. Both species reproduce mainly through the formation of small offsets, or bulblets, attached to the main bulb underground. Wild garlic also produces aerial bulblets at the top of the plant’s stalk in late spring, aiding in its spread. If the foliage is simply pulled, the leaves often snap off, leaving the main bulb and bulblets behind to sprout into new plants. The underground bulbs can remain viable and dormant for several years, making a multi-year control plan necessary for complete removal.
Non-Chemical Removal Techniques
For small patches, manual removal is the most effective non-chemical solution, provided the entire underground structure is extracted. Use a small spade or trowel to dig beneath the plant, ensuring you excavate the main bulb and all attached bulblets, which can be located six inches or more deep. Attempting to pull the plant by hand is ineffective because the brittle leaves break easily, leaving the reproductive bulbs intact below the soil surface.
In garden beds or areas without turf grass, solarization or smothering can control larger infestations. Applying a thick layer of opaque plastic sheeting or heavy organic mulch, such as wood chips, deprives the plants of light. This cuts off the energy supply necessary for the bulbs to produce new shoots, eventually killing the plants over an extended period.
Mowing the foliage will not kill the plants, but it serves two purposes for control. Regular mowing weakens the plant by continually removing photosynthetic tissue, forcing the bulb to use its stored energy reserves. Mowing also prevents wild garlic from developing and dispersing its aerial bulblets in late spring, limiting the spread of new plants.
Selecting and Applying Herbicides
For widespread infestations in a lawn, selective post-emergent herbicides are the most practical solution, since pre-emergent products are ineffective against established underground bulbs. Successful products contain active ingredients such as 2,4-D, dicamba, or fluroxypyr, often found in three-way broadleaf weed killers designed for turf. These selective herbicides target the weeds without harming the surrounding grass.
Timing the application is a factor due to the weed’s cool-season growth cycle. The most effective control is achieved with applications in the fall, typically in November, when the plants are actively growing and moving energy downward to the bulbs. A follow-up application should be made in late winter or early spring, around February or March, before the weeds produce their next generation of bulblets. Multiple applications over two to three years are necessary to deplete the entire population.
The waxy, narrow leaves present a challenge because they prevent herbicide droplets from adhering and penetrating the plant tissue. To overcome this defense, a non-ionic surfactant should be mixed with the liquid herbicide solution before application. The surfactant acts like a wetting agent, allowing the chemical to stick to the foliage and be absorbed more effectively. Experts also recommend lightly bruising the leaves, perhaps by running a mower over the area immediately before spraying, to break the waxy coating and improve herbicide uptake.
Stopping Future Infestations
Long-term management depends on promoting a healthy, dense lawn that crowds out weeds. A thick stand of turf grass creates a strong barrier, reducing the space and light wild onion and wild garlic need to emerge. This is achieved through proper cultural practices, including consistent fertilization, appropriate watering, and aeration to ensure good soil health.
Lawn care should include overseeding thin areas in the fall to increase turf density, closing the gaps where the Allium weeds can sprout. Ensuring the soil pH and nutrient levels are optimal for the desired turf species through soil testing helps the grass out-compete the weeds for resources. A vigorous lawn is a strong defense against all weed invasions.
When manually removing wild onion or garlic, proper disposal of the uprooted material is paramount to prevent re-infestation. The removed bulbs and bulblets should never be added to a compost pile, as they can survive the composting process and remain viable. Instead, the entire clump of plant material, including the surrounding soil, must be sealed in a plastic bag and disposed of with household waste to ensure the reproductive structures are destroyed.