Borage (Borago officinalis) is a self-seeding annual herb, native to the Mediterranean, known for its star-shaped blue flowers and cucumber-flavored leaves. It is often used in culinary and medicinal applications. Deer typically do not eat this herb; borage is widely classified as a deer-resistant plant due to specific physical and chemical defenses it has evolved.
Why Deer Typically Avoid Borage
Deer bypass borage primarily due to its unappealing physical texture and defensive chemical compounds. The plant’s stems and leaves are covered in stiff, coarse hairs, known as prickles or setae. These bristly appendages make borage highly unpalatable and mechanically difficult for a deer to chew and swallow. Deer are selective browsers and prefer smooth, tender foliage that requires minimal effort to consume.
Borage also contains a class of protective compounds called pyrrolizidine alkaloids (PAs). Plants produce these secondary metabolites as a natural defense mechanism against herbivores. While the concentration in borage is relatively low, these alkaloids contribute a distinctly bitter or unpleasant flavor. Deer possess a keen sense of taste that allows them to quickly detect and reject plants containing these defensive compounds. This dual-action defense system of physical discomfort and taste aversion ensures borage remains low on the list of preferred forage.
Situations That Increase Risk of Consumption
While borage is generally avoided, the deer-resistant label is not an absolute guarantee against browsing damage. Deer behavior is largely driven by hunger, meaning they will consume less palatable plants when their preferred food sources are scarce. This risk increases during extreme environmental stress, such as severe drought or deep winter when high-quality forage is unavailable. Under these conditions, the deer’s need for calories outweighs its natural aversion to the plant’s texture and taste.
Elevated local deer population density also increases browsing pressure on all available vegetation, including resistant plants. Competition for food forces deer to expand their diet, leading them to sample plants they would normally ignore. Furthermore, young borage seedlings are more vulnerable than mature plants. At the seedling stage, the bristly hairs and high concentrations of defensive alkaloids have not fully developed, making the young growth more tender and less protected.
Practical Steps for Garden Protection
For gardeners in areas with high deer activity, combining borage’s natural defenses with practical measures provides the best protection. Simple physical barriers are the most reliable defense, especially when the plants are young and susceptible to browsing. Temporarily surrounding small patches of borage with a short wire cage or netting during the initial growth phase prevents damage until the plant matures and develops its full set of natural deterrents.
Strategic placement of borage can also help safeguard other attractive plants in the garden. Borage is an effective companion plant; positioning it as a perimeter around palatable crops like tomatoes or strawberries can help mask their scent. The borage acts as a buffer zone, forcing deer to encounter the unappealing texture and flavor before reaching favored vegetables. Planting borage near areas with frequent human activity, such as a patio or walkway, may also discourage deer from browsing.