Gardeners often seek plants resistant to browsing animals like deer and rabbits, which can quickly devastate flower beds. Geraniums, popular for their vibrant blooms and hardiness, are frequently cited as a natural defense. This article explores the resistance level of geraniums to deer and rabbits and examines the biological mechanisms that deter these animals.
General Resistance to Deer and Rabbits
Geraniums are generally classified as highly resistant to both deer and rabbits, though this does not equate to absolute immunity. They are low on the preference list of both animals and are rarely consumed when other palatable food sources are available. Horticultural studies, such as those from Rutgers University, rate many common Pelargonium types as only “occasionally damaged” by deer.
Resistance is not a guarantee that the plant will never be touched, especially during periods of environmental stress. A desperate animal, such as one foraging during a drought, may still browse on geranium foliage. However, the plant’s natural defenses ensure that deer or rabbits will almost always choose alternatives like hostas or tulips first.
The plant’s effectiveness is a cumulative result of multiple factors rather than a single defense mechanism. These defenses combine to make the plant unappealing to the herbivore’s sense of smell, taste, and touch.
The Chemical and Textural Deterrents
The most potent deterrent is the presence of volatile essential oils concentrated within the foliage. Deer rely heavily on their sense of smell and are repelled by the strong, pungent aroma released when the leaves are crushed. These oils contain terpenoids, such as citronellol and geraniol, which many herbivores find intensely unpleasant.
This powerful scent signals unpalatability and often steers deer away before they attempt to take a bite. Studies using geranium oil confirm its efficacy as a repellent against small herbivores. The plant’s natural fragrance is a significant factor in its defense.
Rabbits are deterred by a combination of texture and taste. Many geranium varieties feature leaves covered in fine, dense hairs, known as trichomes. This fuzzy or coarse surface creates a physical barrier that rabbits dislike chewing, making the plant less appealing than smooth-leaved alternatives.
Additionally, the foliage contains bitter-tasting compounds, including certain alkaloids, which rabbits instinctively avoid. These substances can cause digestive upset, prompting the animal to seek safer forage. This bitter taste acts as a powerful secondary defense.
Distinguishing Between True and Common Geraniums
The name “geranium” commonly refers to two distinct genera within the Geraniaceae family. The annual, upright plants popular in containers are Pelargonium species, often called zonal geraniums. These are typically treated as annuals in cold climates and are characterized by thick stems and a pronounced foliage scent.
The second group is the “true geranium,” or cranesbill, which belongs to the genus Geranium. These are hardy perennials known for their low-growing, spreading habit and ability to survive cold winters. Both Pelargonium and Geranium are generally resistant to browsing animals.
Pelargonium varieties, especially scented types, often have a more intense, bitter compound profile and fuzzier leaf texture, making them a stronger repellent for rabbits. Conversely, some perennial Geranium species, such as Geranium macrorrhizum, are rated as “seldom damaged” by deer. Both the annual Pelargonium and the perennial Geranium are effective choices for discouraging browsing.
Active Measures When Geraniums Are Eaten
When geraniums are unexpectedly eaten, it signals that food scarcity has forced animals to consume non-preferred forage. Gardeners must then supplement the plant’s natural defenses with active interventions. One effective strategy is using odor-based commercial repellents, which utilize strong smells like rotten eggs or botanical oils that deer and rabbits find offensive.
These sprays must be applied directly to the foliage and require reapplication after heavy rain or watering. It is necessary to rotate between different repellent formulations over the season to prevent animals from becoming accustomed to a single scent. Homemade solutions, such as mixtures of eggs and hot sauce, can also serve as temporary taste deterrents.
For persistent problems, physical barriers are the most reliable solution. Low fencing, two to three feet high, is sufficient to discourage rabbits. Protecting plants from deer requires a much taller barrier, ideally a fence at least eight feet high, as deer easily jump shorter obstructions. Motion-activated sprinklers offer a non-physical deterrent by startling the animals with a sudden burst of water.