Groundhogs are common garden pests known for their destructive burrowing and appetite for vegetation. They can rapidly decimate a garden, leading many gardeners to seek natural, plant-based deterrence methods. Employing certain plants creates an aromatic and chemical barrier, making the garden less appealing and encouraging the groundhog to forage elsewhere. This approach offers a sustainable, non-lethal solution for protecting vulnerable crops and ornamental plantings.
Plants Groundhogs Actively Avoid
Groundhogs avoid plants with strong, pungent scents or toxic compounds. Common herbs are excellent for establishing an aromatic defense line. Herbs like mint, chives, rosemary, and oregano release volatile oils that groundhogs find offensive. Planting garlic or members of the Allium family provides a strong deterrent due to their sulfur-containing compounds.
Ornamental flowers containing naturally occurring toxins also deter groundhogs. Daffodils contain alkaloids that are distasteful, causing the animals to leave the bulbs and foliage untouched. Flowers such as foxglove and lily-of-the-valley contain cardiac glycosides, which are toxic to mammals if ingested.
Other deterrent plants rely on acrid flavor or offensive scent, including marigolds and catmint. Marigolds emit a strong, peppery aroma from their foliage due to compounds known as thiophenes. Catmint’s intense, mint-lemon fragrance, derived from nepetalactone, is also an effective repellent.
The Science of Scent and Taste Deterrence
The effectiveness of these plants stems from natural chemical defenses evolved to protect against herbivory. Plants produce secondary metabolites, compounds that act as feeding deterrents by affecting the groundhog’s sense of smell and taste.
Many herbs, such as mint and lavender, contain volatile organic compounds (VOCs), aromatic molecules classified as terpenoids. These essential oils evaporate easily, creating a persistent, repulsive odor that overloads the groundhog’s sensory system. The groundhog perceives these intense smells as a sign of unsuitability, prompting it to bypass the area.
Toxic deterrents rely on bitter-tasting nitrogenous compounds called alkaloids, found in plants like daffodils and foxglove. Alkaloids are often toxic, causing physiological distress, or possess an extremely bitter taste that makes the plant unpalatable. For the Allium family, the pungent effect comes from sulfur-containing compounds like glucosinolates, which break down into irritating isothiocyanates when the plant tissue is damaged.
Strategic Placement for Effective Control
Successful use of deterrent plants depends on strategic placement within the garden landscape. Perimeter planting is the most effective method, creating an aromatic barrier around the entire vulnerable area. Planting dense rows of strong-smelling herbs like mint or lavender along the garden edge establishes a clear boundary groundhogs are reluctant to cross.
The perimeter should have sufficient density and height to create both a physical and olfactory blockade. Intercropping involves placing deterrent plants directly among vulnerable crops, such as planting garlic or chives between rows of beans or peas. This technique effectively masks the attractive scent of preferred food, making the garden plot less appealing for foraging.
Supplementary Non-Plant Natural Deterrents
Combining plant-based defenses with other natural methods increases protection. Physical barriers, such as a sturdy fence, offer the most reliable exclusion against groundhogs. A proper groundhog fence must be at least 3 feet high to prevent climbing and extend 12 to 18 inches below the soil line.
To counteract digging, the buried fence portion should be bent outward in an “L” shape, creating a horizontal barrier beneath the ground surface. Sensory deterrents create an unwelcoming environment, such as motion-activated sprinklers that startle the animal. Groundhogs can also be deterred by ultrasonic devices or wind chimes that introduce unpredictable noise and vibration.
Habitat modification makes the property less attractive for nesting and burrowing. Removing brush piles, overgrown weeds, and debris eliminates potential hiding spots and reduces protective cover. Applying topical repellents around burrow entrances or garden edges can also trigger an avoidance response. These repellents include a mixture of castor oil and water or predator urine.