From a botanical perspective, peonies (Paeonia spp.) possess several inherent characteristics that contribute to their deer-resistant reputation. Their primary defense is not a single trait but a combination of physical and chemical deterrents. The foliage and stems of many herbaceous peony varieties are notably tough and somewhat woody, even during the growth season. This coarse texture is unpalatable to deer, who prefer tender, soft vegetation like hostas, daylilies, and many annuals. Furthermore, the plant contains paeonol, a compound found particularly in the bark of tree peonies and to a lesser extent in other parts of the plant. This chemical, along with other mildly toxic compounds, gives the plant a bitter taste that deer find offensive, leading them to avoid it when more preferable forage is available.
It is crucial to understand that "deer-resistant" is not synonymous with "deer-proof." A plant's resistance is highly dependent on external environmental pressures, primarily the availability of alternative food sources. During most of the growing season, when vegetation is abundant, deer will typically browse on their favorite plants and leave peonies alone. They sample vegetation and quickly learn to associate the peony's bitter taste and tough texture with an undesirable meal. However, in times of extreme hunger, such as a harsh winter or a severe drought when their preferred food sources are depleted, deer are far less discerning. Under these conditions of high pressure and scarce resources, they may eat plants they would normally avoid, including peonies, especially the emerging tender buds in early spring.
From the plant's standpoint, not all parts are equally protected. The mature, leathery leaves and established stems are the least palatable due to their high concentration of fibrous tissue and bitter compounds. The large, often sticky flower buds in spring are slightly more vulnerable because they are a nutrient-rich package, but their strong flavor still often protects them. The fully opened, fragrant flowers can sometimes be a target, not necessarily for consumption, but out of curiosity or by accidental damage as deer navigate the garden. It is important to note that deer resistance can also vary by peony variety. Some hybridizers may inadvertently select for traits that reduce bitterness or produce softer foliage, which could make a specific cultivar slightly more appealing than others.
To effectively protect peonies and other plants, a multi-layered, strategic approach is best. This mimics the diversity of a natural ecosystem. Planting peonies alongside other strongly-scented and reliably deer-resistant plants like lavender, sage, catmint, or Russian sage can create a sensory barrier that helps to mask the scent of more vulnerable plants. The most reliable physical method is the use of barriers. This can involve spraying a deer-repellent spray directly onto the peony's emerging shoots and buds. These sprays work by emitting an odor that deer associate with predator urine or by adding another layer of bitter taste. For persistent deer populations, physical fencing, even if just 6-8 feet tall around the garden's perimeter, remains the only guaranteed method of protection, effectively separating the deer from all desirable plants.
