The sweet pea, Lathyrus odoratus, is a beloved garden annual known for its intense fragrance and vibrant flowers, often cultivated on trellises and arches for vertical color. As deer populations expand into residential areas, the risk of browsing damage to ornamental plants has become a common concern. Gardeners must determine if deer will target the sweet pea, a plant that possesses certain natural defenses.
Deer Interest in Sweet Peas
Sweet peas are generally classified as a less-preferred food source for browsing deer, but this does not make them deer-proof. The plant contains toxic compounds, most notably the amino acid derivative beta-aminopropionitrile (BAPN). This chemical gives the foliage a bitter taste, which most deer instinctively avoid when other, more palatable food is available. This chemical defense mechanism makes the sweet pea a low-priority target for a well-fed herd.
Deer can detect and remember plants that could cause them digestive upset. However, this deterrence is not absolute, and the plant is not entirely safe from being consumed. Deer have been observed to nibble on the foliage and flower buds, particularly when testing out new food sources. When browsing pressure is high, or preferred vegetation is scarce, deer will override their natural aversion to bitter or slightly toxic plants.
Variables That Affect Deer Foraging
The likelihood of sweet peas being damaged is heavily influenced by environmental pressure and the deer’s local diet. When natural food sources are limited, such as during severe drought or the lean winter months, deer become far less selective. Their need for calories compels them to consume plants they would normally ignore, including those with bitter chemical compounds. This scarcity is the biggest factor that can turn sweet peas from an avoided plant into a viable food source.
Deer foraging behavior is also linked to the plant’s maturity and the regional palate of the local herd. Deer generally prefer the tender, high-nutrient growth of young plants and new shoots over older, tougher foliage. Newly transplanted sweet peas or fresh spring growth are at a higher risk of being eaten than established vines. Deer in different geographic regions can develop unique preferences, meaning a plant left alone in one area may be heavily browsed in another.
The deer’s habituation to human proximity plays a role in their willingness to enter a garden and browse. In residential areas where deer frequently encounter people, they are less wary of taking risks. Once a deer discovers a food source, even a slightly unappealing one like sweet peas, it will likely return repeatedly. This learned behavior underscores the importance of employing effective deterrents immediately.
Methods for Deterring Deer Damage
The most reliable method for protecting sweet peas is the installation of physical barriers. Because deer are exceptional jumpers, a fence must be at least eight feet high to provide consistent exclusion in open areas. In smaller, enclosed yards, a six to seven-foot fence may be sufficient, as deer are hesitant to jump into a confined space. An alternative is a double-fence system, where two lower fences are placed several feet apart, which deters deer from attempting the jump.
Chemical deterrents offer another layer of protection, working primarily through taste or smell aversion. Repellents containing ingredients like putrefied egg solids, garlic, or capsaicin create an unpleasant experience that encourages the deer to forage elsewhere. These products include contact repellents, applied directly to the foliage, and area repellents, used on the garden perimeter to create a scent barrier. To maintain effectiveness, repellents must be rotated frequently to prevent habituation and reapplied regularly after rain or when new growth emerges.