Irises are popular garden plants, and for gardeners dealing with browsing animals, their resistance to deer is a primary concern. Irises are generally considered deer resistant, but they are not entirely deer-proof. Deer consistently choose other plants over irises due to a combination of unappealing characteristics. Understanding the biological reasons for this avoidance helps manage gardens in areas with high deer populations.
The Reason Deer Avoid Irises
The primary defense mechanism in the Iris genus stems from natural chemical compounds that are unpalatable and toxic to grazing animals. These compounds include iridoid glycosides, which impart a bitter taste to the foliage and rhizomes. This bitter flavor acts as a significant deterrent, as deer rely heavily on taste and smell to identify safe forage.
These defensive chemicals are concentrated throughout the plant, especially in the underground rhizomes. Ingestion of these glycosides, or other toxic substances like lycorine, can cause gastrointestinal distress, making the plant an undesirable food source. The strong scent and the tough, fibrous texture of the leaves also contribute to the plant’s low appeal.
Factors That Increase Deer Damage
While irises possess strong natural defenses, specific conditions can increase the likelihood of deer browsing and damage. The most significant factor is severe food scarcity, typically brought on by environmental stress such as prolonged drought, heavy snow cover, or late winter conditions. In these desperate circumstances, a hungry deer will sample and consume plants it would normally ignore, including irises, simply for moisture and bulk.
Damage is also often observed on new or young foliage, which may contain lower concentrations of the bitter-tasting compounds compared to mature leaves. Tender new shoots emerging in early spring are more appealing, and deer may sample these before moving on to find a more palatable meal. This “sampling damage” usually means the deer quickly realized the plant was still unappealing and did not consume the entire clump. New hybrid varieties may also occasionally have slightly reduced chemical defenses compared to older, hardier species, making them marginally more vulnerable to browsing.
Protecting Your Iris Garden
For gardeners in areas with significant deer pressure, a combination of physical and sensory deterrents offers the most effective protection. Physical barriers are the most reliable method, ranging from a seven-to-eight-foot-tall fence, which is necessary to fully exclude deer, to temporary netting placed over smaller plantings. Short-term physical barriers, like hardware cloth bent over new sprouts, can protect vulnerable foliage until the plants are larger and less appealing.
The use of commercial deer repellents, which employ strong tastes or odors like rotten eggs or garlic, can be effective but requires regular reapplication. These sensory deterrents must be reapplied frequently, especially after rain or as new foliage emerges, to maintain a consistent barrier. Strategic planting can also offer a degree of protection by placing irises closer to a house or a high-traffic area, which deer generally avoid. Interplanting irises with highly fragrant, deer-resistant companion plants like alliums or lavender can further mask the irises and make the area less inviting for browsing.