Cosmos flowers, with their delicate, daisy-like appearance, are a popular choice for gardeners seeking an easy-to-grow annual that provides continuous color. A common question for those who share their space with wildlife is how palatable they are to deer. This article explores the specific traits of the cosmos flower that influence a deer’s dining decisions.
The Level of Deer Resistance
Cosmos are consistently classified by horticultural experts as moderately deer-resistant, meaning they are seldom a preferred food source. Deer usually bypass cosmos in favor of more appetizing plants nearby. The term “deer-resistant” signifies a low-preference food rather than a guarantee of safety.
No outdoor plant can be considered completely “deer-proof.” Gardeners can expect damage to be rare, but should not assume the plants are entirely immune to browsing. This low-preference ranking makes cosmos a reliable choice for landscapes where deer are a regular presence.
Natural Factors That Repel Deer
The deer’s aversion to cosmos is driven by specific biological and textural characteristics. One significant deterrent is the taste and odor produced by the plant’s chemistry. Cosmos contains aromatic compounds that deer find bitter or strongly unpleasant, causing them to move on to less noxious forage.
The physical texture also works against a deer’s preference for soft, easily digestible foliage. Deer prefer plants that are easy to chew, but the slender stems and fern-like leaves of Cosmos bipinnatus feel unappealing in their mouths. This combination of strong flavor and undesirable texture signals the deer to seek food elsewhere.
Why Deer Occasionally Browse Cosmos
Despite the plant’s natural defenses, specific environmental and situational factors can override a deer’s typical aversion. The most common cause is extreme hunger, particularly during periods of drought or late winter when preferred food sources are scarce. When a deer’s usual browse is unavailable, the animal may resort to eating plants it normally avoids.
Another contributing factor is a high local deer population, which increases competition for food. In areas with dense herds, the animals are forced to expand their diet to survive, leading to browsing on less-palatable plants. Furthermore, young or newly planted cosmos are often more vulnerable. Their tender stems and leaves have not yet fully developed the strong aromatic compounds that deter mature deer.
Supplementing Cosmos Protection
Gardeners in high-pressure deer areas should implement supplementary protection to guarantee their cosmos’ safety.
Physical Barriers
One of the most effective strategies is the use of physical barriers, such as temporary netting or chicken fencing, around new plantings or small beds. For permanent protection, a woven-wire fence must be at least eight feet high to prevent deer from jumping over it.
Repellents
Repellents offer another layer of defense by targeting a deer’s sense of smell and taste. Commercial or homemade repellents based on ingredients like eggs, garlic, or capsaicin create a foul smell and bitter taste that discourages browsing upon contact. These liquid sprays must be reapplied every few weeks and after heavy rain to maintain their effectiveness.
Companion Planting
A simple technique is companion planting, which involves strategically placing cosmos near plants deer actively dislike. Highly fragrant herbs such as lavender, sage, or rosemary can mask the scent of the cosmos. This creates a natural, aromatic perimeter that makes the area less inviting to foraging deer.