The common snapdragon (Antirrhinum majus) is a vibrant garden favorite generally considered highly deer-resistant. Deer are selective browsers, but this resistance is not a guarantee of protection; snapdragons are resistant but not entirely deer-proof. The plant’s inherent traits make it an unappealing food source, and it is rarely damaged when more palatable options are available.
Deer Resistance: Why Snapdragons Are Often Ignored
Snapdragons possess specific chemical and physical characteristics that act as natural deterrents to grazing mammals. The primary defense mechanism is chemical, involving the presence of compounds known as saponins and iridoid glycosides. These secondary metabolites create an intensely bitter flavor that deer find unpalatable upon initial sampling, prompting them to seek out agreeable vegetation.
These bitter compounds serve as a protective warning, as ingesting large amounts can cause mild digestive upset in mammals. Beyond the taste, the snapdragon also presents a less desirable texture. Its foliage is not tender or succulent like the plants deer prefer, and the leaves and stems are protected by small, hair-like structures called trichomes.
These glandular hairs create an unpleasant, fuzzy or greasy mouthfeel for the deer. Although a deer may take an exploratory bite, the combination of bitter taste and unappealing texture usually convinces the animal to move on. This multi-layered defense system classifies the plant as reliably avoided under normal foraging conditions.
Situational Factors That Override Resistance
A plant’s deer resistance is highly situational, and external pressures can cause deer to consume even the most protected species. The most common cause for browsing snapdragons is a scarcity of preferred food sources, often triggered by environmental conditions. During severe drought or harsh winter weather, the lack of tender, native forage forces deer to widen their diet.
High deer population density is another factor that eliminates the protective effect of resistance. When the population exceeds the habitat’s capacity, deer rapidly deplete preferred plants, leading to intense competition for remaining resources. This ecological pressure leaves resistant plants like snapdragons as the only available option, making them a necessary, though disliked, meal for survival.
Furthermore, the age of the plant material influences its palatability, particularly in the spring. New, tender growth is generally less fibrous and contains lower concentrations of the bitter saponins than the fully matured foliage. This makes the young shoots of snapdragons more vulnerable to browsing early in the season before the plant has fully developed its chemical defenses.
Practical Steps for Protecting Snapdragons
For gardeners in areas with high deer traffic, localized protection methods can reinforce the snapdragon’s natural resistance. The most effective approach involves using repellents that target a deer’s sensitive sense of smell and taste. Scent-based sprays containing putrescent egg solids or strong essential oils should be applied directly to the foliage.
These contact repellents make snapdragons smell and taste worse, but they must be reapplied every few weeks and after heavy rain. Granular repellents, which often contain blood meal or predator urine scents, can be applied around the perimeter of the flower bed. These create a localized scent barrier that deters deer from entering the area.
Physical barriers offer the most reliable localized solution, especially for new spring plantings. Temporary, lightweight polypropylene netting with a three-quarter-inch mesh size can be draped over newly planted snapdragons or secured using short stakes. This simple measure creates a physical obstruction that deer are reluctant to push against, protecting the vulnerable young plants until they mature and their natural resistance fully develops.