Irises (Iris spp.) are prized garden perennials known for their colorful blooms and sword-like foliage. The plant defends itself chemically with irritating compounds (iridin and irisine) that usually deter most generalist herbivores from consuming the leaves or flowers. However, this defense is not universally effective, and certain determined pests still target the plant. These pests often focus on the underground rhizome, where the toxin concentration is highest. Identifying the animals responsible and their specific feeding habits is necessary for implementing targeted protection strategies.
Primary Animal Culprits That Graze
Certain animals still graze on iris leaves and flowers, often when preferred food sources are scarce. The most common above-ground culprits are white-tailed deer and rabbits. Deer browse opportunistically, viewing garden beds as accessible food, especially during winter or early spring.
Rabbits target low-growing vegetation, focusing on tender new shoots and young foliage closer to the ground. Both mammals can cause significant damage quickly, leaving distinct clues for the gardener. Smaller grazers, like slugs and snails, cause cosmetic damage by rasping away soft leaf tissue. These mollusks are active during damp conditions, leaving irregular holes in the foliage.
Identifying Specific Damage Patterns
Identifying the perpetrator requires examining the physical evidence left on the plant tissue. Deer lack upper incisors, forcing them to grasp and tear the material they consume. This results in a ragged, frayed, or shredded appearance on the remaining iris stalks and leaves.
Rabbit damage, in contrast, is characterized by a clean, sharp cut, often appearing at a 45-degree angle. Rabbits use razor-sharp incisors to snip through stems and leaves with precision, resembling deliberate pruning. Slugs and snails are diagnosed by their unique trails. The telltale sign of their nocturnal activity is the silvery, dried mucus trail deposited on the foliage and surrounding soil.
Deterring Above-Ground Feeders
Protecting irises from grazers involves physical barriers and deterrents. Fencing is the most reliable protective measure, but required height varies significantly between the main culprits. To deter deer, a fence must be eight to ten feet tall, as they jump considerable heights when motivated.
For rabbits, a two to three-foot fine-mesh wire barrier is sufficient. This low fence must be secured or buried a few inches into the ground. Burying the barrier prevents rabbits from digging underneath and accessing the protected plants.
Repellents offer a non-barrier approach, working by taste or smell to make plants unappealing. Commercial products often contain putrescent egg solids, which emit an odor highly unappealing to deer and rabbits. Other options include scent-based deterrents like dried blood or strongly scented bar soaps, which require frequent reapplication, especially after rain or irrigation.
It is important to rotate the type of repellent used, as deer and rabbits can become quickly habituated to a single scent or taste over time. Combining different strategies, such as alternating between a scent-based spray and a taste repellent, enhances the long-term effectiveness of the chemical defense.
Cultural controls also reduce the garden’s appeal. Removing dense ground cover, brush piles, and low-hanging branches near iris beds eliminates the protective cover rabbits rely on for shelter. Companion planting with highly aromatic herbs or other plants known to be unpalatable to grazers can create a buffer zone around the irises, making them less visible and accessible.
Managing Burrowing Pests
The most destructive pests operate underground, targeting the rhizome. Voles and gophers are the main subterranean threats, and their feeding is damaging because they consume the part of the plant with the highest concentration of toxins. Gophers can cause the entire iris plant to disappear suddenly by pulling it into their tunnels.
Protecting the rhizomes requires specialized intervention, often focused on exclusion during planting or division. Individual irises can be planted inside wire cages or baskets made from hardware cloth. These barriers must be wide enough for lateral growth but shallow enough to protect the root mass without constriction.
Trapping Methods
Trapping is a highly effective control measure once an infestation is established and is often preferred over baiting due to safety concerns for non-target animals. Gophers are best controlled using specialized two-pronged pincer traps placed directly inside their main tunnels. For voles, standard spring-loaded mousetraps set perpendicular to their visible above-ground runways are highly successful. Eliminating dense vegetation and high grass immediately surrounding the iris beds also removes the protective cover voles rely on for surface activity, making the area less attractive for nesting and feeding.