While no plant can be considered completely deer-proof, as a starving deer will eat almost anything, Paeonia lactiflora and other common garden peonies are generally classified as deer-resistant. This resistance is not due to a single factor but rather a combination of the plant's physical and chemical properties that make it unpalatable and less attractive to browsing deer.
The primary defense of the Paeonia lactiflora plant against deer browsing is its chemical makeup. Peonies contain compounds that are distasteful to deer. Most notably, they contain paeonol, a compound found in the bark of the peony root, which is also present in other parts of the plant. This substance, along with tannins and other bitter-tasting chemicals, creates an unpleasant flavor profile for deer. When a deer samples a peony, the bitter taste acts as a strong deterrent, encouraging the animal to move on to more appealing vegetation. Furthermore, peonies do not produce the types of volatile aromatic compounds that attract herbivores to many other garden plants.
Beyond their chemical defenses, the physical structure of peonies contributes to their deer resistance. The foliage and stems of Paeonia lactiflora are notably tough and fibrous. Deer prefer tender, succulent, and easily digestible shoots and leaves. The robust, almost leathery texture of mature peony leaves is unappealing and difficult for them to chew and digest. The woody nature of the stems, especially as the season progresses, further reduces their attractiveness as a food source compared to softer-stemmed plants like hostas or daylilies, which are deer favorites.
It is important to note that peonies are considered mildly toxic to humans and pets if ingested in large quantities due to the presence of paeonol and other compounds. This inherent toxicity also extends to deer and other herbivores. While not typically lethal, consumption can cause gastrointestinal upset, including nausea, vomiting, and diarrhea. Deer, through instinct or learned behavior, tend to avoid plants that cause them discomfort, further reinforcing the peony's status as a deer-resistant selection for the landscape.
A critical point of consideration is the stage of plant growth. In early spring, the emerging red shoots of the peony are tender and may be more susceptible to curious deer tasting them. However, because the plant's unpalatable compounds are present even in new growth, these instances are usually limited to a single bite before the deer moves on. The most significant risk is not the deer eating the entire plant but rather the accidental damage they may cause by trampling through the garden bed. During periods of extreme drought or in winter when preferred food sources are scarce, deer may be more likely to sample plants they normally avoid, including peonies.
