Are Mexican Marigolds Poisonous to Moles?

Meddlesome Moles

• If you have moles in your garden, you know the destruction they cause. And although it may seem as if your landscape is full of them, moles are solitary creatures -- you likely don't have more than two in your garden. Still, just two moles can create a lot of tunnels, damaging the roots of your plants in the process. In fact, if you think moles are eating your plants, think again: Moles are carnivores -- they rarely eat plant material. Instead, they tunnel through the rich soil of your garden in search of insects to eat. As a result, your plants are dying because the activity of the moles is damaging their roots, or because bulb-eating rodents are following the trails moles create to access your plants. Either way, the best solution is to get rid of the moles. Although trapping is the best way to get rid of a mole, it won't prevent more moles from moving in. For that, you need a way to repel them.

Smelly Plant

• The Mexican marigold has a strong scent that repels moles and, as an added bonus, wild rabbits. The scent also repels bothersome insects such as the Mexican bean beetle and other plant-eating bugs. Because the scent is so strong, however, it may have an herbicidal effect on nearby vegetables such as cabbage and bean plants, according to California Lutheran University. For this reason, it's best not to plant Mexican marigolds directly next to edibles. Instead, plant several Mexican marigolds as a protective border around your garden. Or, plant it as a cover crop at least two months before planting vegetables, and then till it under before you sow any vegetable seeds. This will get rid of nematodes as well as help to repel moles.

Attractive and Useful

• The subtle beauty of the Mexican marigold lends itself well to perennial gardens in warmer climates, and home gardeners in colder climates can grow it in a container and bring it indoors for the winter. The plant grows to a maximum height of about 30 inches and features small yellow flowers that cluster atop the stems. The leaves are glossy green and line the tall, slender stems. Not only is the Mexican marigold attractive, but also it is useful. Moles may not appreciate the scent of the plant, but home gardeners who like tarragon will be glad to add the Mexican marigold to their gardens.

Culture & Care

• The Mexican marigold grows best in U.S. Department of Agriculture plant hardiness zones 8 through 11. In USDA zone 8, the plant will likely die to the ground during a hard frost, but will sprout again come spring. It thrives in full sun and in rich, well-draining soils -- good drainage is a must, according to Arizona State University. The Mexican marigold is drought tolerant and is not usually bothered by pests -- including moles.

Repelling Moles

• The Mexican marigold will not poison your mole, but it should repel it to some extent. Other plants that will also repel moles -- with the added benefit of being toxic -- include caper spurge (Euphorbia lathyris) and the castor oil plant (Ricinus communis), both annuals. Although the caper spurge plant is mildly toxic, the castor oil plant is extremely dangerous and you should not plant it in gardens accessible to children or pets.