Ageratum houstonianum, commonly known as Floss Flower, is a popular annual bedding plant recognized for its distinctive, fluffy pom-pom blooms. These flowers introduce soft textures and cool colors, predominantly shades of blue, purple, and white, to garden beds. Gardeners often seek to know if this plant is safe from browsing wildlife. While no plant is entirely deer-proof, Ageratum is categorized as a deer-resistant option generally avoided by foraging deer.
Ageratum’s Natural Deterrents
Floss Flowers possess several natural defense mechanisms that make them unappealing to deer, which rely heavily on scent and taste to select their food.
The primary deterrent is the plant’s chemistry. Ageratum contains bitter-tasting compounds known as pyrrolizidine alkaloids. These substances are toxic to grazing animals and can cause liver lesions if ingested in significant amounts.
The plant’s physical texture also contributes to its low palatability. Ageratum leaves and stems are often covered in small, fine hairs, giving them a fuzzy surface. Deer prefer plants with smooth, tender foliage, and the rough texture of Ageratum is uncomfortable for them to chew, prompting them to seek out smoother alternatives.
In addition to the texture and toxicity, the plant emits a strong, distinct aroma that deer find disagreeable. Deer have an extremely sensitive sense of smell, which they use to detect palatable food sources. The intense fragrance of the Floss Flower acts as a repellent, causing deer to bypass it in favor of less aromatic vegetation.
Factors That Increase Deer Browse
Although Ageratum is naturally unappetizing, its resistance is not absolute and can break down under environmental stress. The most common reason deer browse resistant plants is a severe lack of preferred food sources. This often occurs during periods of deep snow cover or extreme summer droughts when succulent forage becomes scarce.
In times of scarcity, a deer’s foraging behavior shifts from selective browsing to survival feeding. Gardens located in areas with a high deer population density are also more likely to experience damage. Increased competition for limited resources forces deer to be less discriminating in their diet, leading them to sample less palatable plants.
If deer are already grazing in a garden due to the presence of highly favored plants, they may occasionally sample the Ageratum out of curiosity. The deer’s initial taste test, however, is often enough for them to quickly abandon the plant due to its bitter flavor. Deer learn quickly to avoid sources of discomfort or poor nutrition.
Practical Deer Deterrence Methods
Gardeners facing high deer pressure can employ a combination of strategies to ensure the safety of Ageratum and other plantings.
Physical Exclusion
Physical exclusion is the most reliable method. This often involves installing a perimeter fence that is at least eight feet tall, as deer are capable of jumping considerable heights. For smaller, isolated areas, netting or wire cages can be placed directly over the plants to create a protective barrier.
Chemical Repellents
Chemical repellents offer a practical solution, working either by foul odor or unappealing taste. Taste-based sprays, which often contain ingredients like putrescent egg solids or capsaicin, must be applied directly to the foliage. Repellents must be reapplied regularly, especially after rain or new growth emerges. It is important to rotate between different types of repellents, such as switching from a scent-based to a taste-based product, to prevent deer from becoming accustomed to a single deterrent.
Companion Planting
A simple and effective approach involves using companion planting to mask the scent of more vulnerable plants. Placing Ageratum near highly fragrant herbs like rosemary, sage, or lavender utilizes their pungent aromas as a natural, secondary line of defense. This strategy leverages the deer’s sensitive nose, making the entire area less desirable for foraging.