Moles are small, subterranean insectivores that damage lawns and gardens through extensive tunneling. Although they do not typically eat plant roots, their digging creates unsightly ridges and mounds, disrupting root systems and leading to dead patches of grass. Utilizing specific plants with natural repellent qualities offers a sustainable, non-lethal method for discouraging these burrowing mammals from inhabiting your property.
The Mechanism: Why Moles Avoid Certain Plants
The effectiveness of plant-based repellents stems from two primary biological factors that interfere with a mole’s sensitive subterranean existence. Moles rely heavily on their sense of smell to navigate tunnels and locate their primary prey, mainly earthworms and grubs. Plants with strong, pungent odors release volatile organic compounds into the soil, creating a sensory disruption that moles find offensive and disorienting. The chemical barrier essentially masks the scent of their prey, forcing them to seek feeding grounds elsewhere.
The second mechanism involves root toxicity, where certain plants produce compounds that are irritating or harmful if ingested or contacted. While moles are insectivores, their foraging behavior means they often come into contact with plant material. The presence of these compounds in the soil acts as a subterranean warning signal, prompting moles to reroute their tunnels away from the source of irritation.
Specific Plant Recommendations for Deterrence
Toxic Repellents
Certain plants contain natural compounds that are toxic to small mammals, making them effective mole deterrents. The Castor Bean plant (Ricinus communis) is recognized for its repellent properties, primarily due to the presence of ricin in its seeds. Similarly, the Crown Imperial Fritillaria (Fritillaria imperialis) deters moles because its bulbs contain a highly odorous and toxic alkaloid. The Daffodil (Narcissus spp.) is another common repellent, as its bulbs and foliage contain the alkaloid lycorine.
This compound is toxic and distasteful to small animals, which discourages them from digging in the surrounding soil. A strong caution must be observed with all toxic plants, especially Castor Bean and Daffodils, as they pose a significant danger to children and pets if ingested. These species should be planted in locations inaccessible to curious animals and kept out of vegetable gardens.
Odorous Repellents
A safer category of deterrents includes plants that rely on strong, pungent aromas to interfere with the mole’s sense of smell. Marigolds (Tagetes spp.) are popular choices, as their roots release a chemical called alpha-terthienyl, which has a sharp, overwhelming scent. Marigolds also help reduce the number of nematodes in the soil, making the area less appealing for foraging.
Alliums, the ornamental relatives of onions and garlic, release sulfenic acids when their roots or leaves are disturbed, creating an intensely oniony aroma that moles dislike. Mint (Mentha spp.) is also effective due to the strong menthol oils released by its roots and crushed leaves, which create sensory confusion for tunneling moles. These fragrant options are generally safer for areas frequented by pets or children, though they require dense planting to achieve an effective concentration of scent in the soil.
Strategic Planting and Managing Expectations
Successful mole deterrence depends on the strategic application of plants within the landscape. The goal is to create a continuous, concentrated barrier that forces moles to change their established routes. This is best achieved through mass planting, grouping multiple repellent plants closely together to maximize chemical concentration in the soil. Gardeners should focus on creating perimeter barriers around the boundary of the area they wish to protect. Another strategy is spot planting, which involves placing repellent bulbs or plants directly into active tunnels or along existing mole runs.
If the repellent plants are toxic, they should be located away from areas of high foot traffic to reduce the risk of accidental contact or ingestion. It is important to correctly identify the pest causing the damage, as moles are often confused with voles. Moles are insectivores that tunnel in search of worms and grubs, leaving raised ridges and mounds of soil. Voles are herbivores that primarily eat plant roots, leaving behind shallow surface runways and gnawed vegetation. While many toxic plants deter both pests, misidentification can lead to frustration if the problem is root-eating voles.
Plant-based methods function as deterrents, not immediate extermination solutions, so managing expectations is necessary. These plants may shift the mole’s activity to a less desirable area of the yard rather than eliminate them entirely. For the best results, consistency is required, and new tunnels should be addressed promptly by adding more repellent plants or applying a castor oil solution. The effectiveness of a plant barrier is often enhanced by reducing soil moisture, as moles prefer damp ground where their insect prey thrives.