Marigolds (Tagetes spp.) don't repel rodents, such as mice, voles, rats, squirrels, chipmunks and groundhogs. Recommended deterrents for these unwanted garden visitors vary based on the species. Conversely, research shows that certain chemical compounds in marigolds and exuded by their roots are effective at warding off insects, such as hornworms, whiteflies and root nematodes. It is possible, horticulturists say, that these compounds also repel moles, which are not rodents but insectivores. More research is necessary to determine whether marigolds ward off moles.
Modifying Habitat to Discourage Rodents
Cleaning up a yard to minimize hiding places is a good way to limit rodents. Grass should be kept trimmed and piles of debris removed. Removing ivy ground cover eliminates a hiding place for rats. Cutting back excess vegetation at ditches and the edges of the yard is a good idea as is pruning low branches that create hiding places under trees and shrubs. Rutgers University adds that it is necessary to seal off areas under storage buildings, steps or decks.
Ways to Deter Rabbits
One of the best ways to deter rabbits is to surround gardens and new trees with chicken wire fencing that has 1-inch-square openings, according to Rutgers University. For garden fencing, sink the chicken wire about 6 inches down into the soil. Placing a tube of fencing around a tree prevents rabbits from stripping bark off the base of the trunk.
Mouse and Vole Controls
Tiny rodents such as mice and voles, which look a bit like hamsters, are hesitant to travel out in the open above ground in case predators are looking for a meal. The Botanique Nursery website suggests creating an open trench around a garden, digging down to hard ground. Botanique says most voles tunnel right beneath the soil's surface and turn back when they reach the exposure of a trench.
Marigolds and Moles
The Internet Center for Wildlife Damage Management says that planting the perimeter of a garden with marigolds "may repel moles from gardens," but this method of pest management hasn't been proven scientifically. The center is a college consortium, including Clemson and Cornell universities, the University of Nebraska and Utah State University.
The center says that although moles don't eat plants as they "swim" through the soil in search of insects, they "may damage plants by disrupting their roots." Also, their tunnels provide protective routes for smaller rodents to raid plants. So minimizing moles would minimize rodent damage by eliminating their underground freeway.