The belief that planting marigolds can protect a lawn or garden from mole damage is a long-standing piece of gardening folklore. This home remedy is based on the plant’s strong aroma and its proven ability to deter certain microscopic pests. It is important to investigate the scientific validity of using Tagetes species, or marigolds, to control these subterranean mammals. The effectiveness of any repellent must be measured against the mole’s natural instincts and constant drive for food.
Understanding Mole Behavior
Moles are small insectivores, meaning they primarily consume insects and other invertebrates, distinguishing them from rodents. Their diet is composed mainly of earthworms, insect larvae, and grubs, which they find by tunneling through the soil. Moles possess a high metabolism that compels them to eat between 70 to 100 percent of their body weight daily to survive. This intense requirement for food drives their constant digging; they can tunnel up to 20 feet per hour in search of prey. The raised ridges and mounds seen in lawns are collateral damage from their relentless foraging, not the result of them eating plant roots.
The Marigold Claim and Rationale
The theory behind using marigolds as a mole repellent centers on the powerful odor they emit. Specifically, certain species, such as the French marigold (Tagetes patula), produce potent compounds called thiophenes in their roots. These chemicals are released into the surrounding soil and are scientifically confirmed to possess biocidal and nematicidal properties. The thiophenes effectively control plant-parasitic nematodes, which are microscopic soil worms that attack plant roots.
Gardeners often correctly observe that marigolds reduce certain soil pests, but this success is frequently misapplied to the larger problem of moles. The strong root exudates also deter certain insects, such as aphids and whiteflies, making the plant popular in companion planting. However, confusion arises from assuming a chemical toxic to microscopic worms will also deter a medium-sized, hungry mammal. Moles rely primarily on detecting soil vibrations and scents related to their prey.
Scientific Verdict on Repellency
Despite the popular belief, there is no reliable, peer-reviewed scientific evidence demonstrating that marigolds repel moles. University extension services list planting Tagetes species as a traditional remedy, but confirm a lack of formal research supporting the claim. The mole’s biological imperative to hunt for earthworms and grubs often overrides any mild repellent effect from the marigold’s root chemicals. Moles are known to tunnel directly through the roots if a concentrated food source lies beyond the plants.
The proven effectiveness of marigolds is limited to controlling plant-parasitic nematodes, which are a completely different class of organism than moles. While the root secretions are toxic to tiny soil organisms, they do not produce enough volatile organic compounds to consistently drive away a large mammal. Scientific studies prioritize trapping and habitat modification for mole control, confirming that planting marigolds is not an effective management strategy.
Effective Mole Management Strategies
Since marigolds are not a proven solution, a more effective approach involves habitat modification and direct control methods. The most successful strategy is trapping, which eliminates the animal directly from the tunnel system. Traps, such as the scissor or harpoon types, must be correctly placed in active, primary foraging tunnels.
Reducing the mole’s food supply through grub control is another effective tactic, making the area less attractive. Applying biological or chemical controls for white grubs, a favorite mole food, can cause the moles to move elsewhere. Physical exclusion is also a viable method, involving the installation of a wire mesh or hardware cloth barrier. This barrier must be buried at least two feet deep around the perimeter of a garden bed, creating an underground fence that moles cannot easily penetrate.