Wax Begonias (Begonia semperflorens) are among the most popular annual bedding plants, prized for continuous flowering in both shade and sun. Gardeners frequently turn to them as a reliable source of color, especially in areas with high deer traffic. They are generally avoided by deer, but this resistance is not the same as immunity. This distinction means the plant is not a preferred food source, which explains why browsing sometimes still occurs.
The Natural Defenses of Wax Begonias
The typical rejection of wax begonias by deer is a result of the plant’s natural chemical and textural defenses. The foliage of Begonia semperflorens possesses a slightly bitter or unpleasant taste that makes it unpalatable to most browsing animals. This bitterness comes from specific compounds the plant produces to deter herbivores.
A specific defense mechanism involves the presence of oxalic acid, which forms calcium oxalate crystals within the plant tissues. When the begonia is chewed, these microscopic, needle-shaped crystals cause a physical and chemical irritation in the mouth and throat of the animal. This unpleasant sensation serves as a powerful deterrent, signaling to the deer that the plant is not a good source of forage.
The physical structure of the wax begonia also contributes to its low appeal. The leaves are waxy and somewhat leathery, and the stems are fleshy and watery, offering little nutritional value compared to other available vegetation. Deer are selective browsers, and they will instinctively choose plants that provide better calories and protein without the associated bitter taste and internal irritation.
When Deer Ignore “Resistant” Plants
While the begonia’s defenses are strong, they are not absolute, and deer sometimes consume them under specific external pressures. The primary reason resistance breaks down is environmental stress leading to hunger, such as during severe drought or late winter when preferred food sources are scarce. When a deer faces starvation, its willingness to tolerate a bitter or irritating taste increases dramatically, making the begonia a viable option.
High deer population density also forces a change in feeding habits. As competition for palatable plants increases, deer must expand their diet to include less desirable vegetation, which includes wax begonias. In these high-pressure zones, the animal is left with fewer choices and must settle for the resistant plants.
New or young growth on begonias is particularly vulnerable to browsing. The tender new shoots often have a lower concentration of the defense compounds, such as oxalic acid, making them less irritating than the mature foliage. Additionally, fawns may browse on plants their mothers typically avoid as they are still learning which plants are acceptable forage, which can lead to initial damage.
Practical Solutions for Protecting Your Garden
When the natural defenses of the wax begonia prove insufficient, gardeners must implement a layered strategy. Physical barriers offer the most reliable protection against persistent browsing pressure. Temporary plastic netting or wire cages can be placed around beds, or begonias can be grown in elevated hanging baskets or window boxes out of the deer’s reach.
Chemical deterrents are another effective tool, but they must be managed to maintain effectiveness. Applying commercial scent-based or taste-based repellents directly to the plants creates an immediate barrier. To prevent deer from becoming accustomed to a single product, rotate between two or three different types every few weeks.
Reapply these sprays immediately after heavy rainfall or when new growth appears, as the fresh foliage will not be protected. Companion planting can provide an additional line of defense by surrounding the begonias with plants that are truly distasteful to deer, such as strongly scented herbs like lavender or plants with toxic properties like daffodils.