From a botanical perspective, the question of a plant's deer resistance hinges on its physical and chemical characteristics. Gladiolus, a genus of perennial cormous plants in the Iridaceae family, possesses certain traits that influence its appeal to deer. The corm itself, which is an underground storage organ, is starchy and could be a potential food source. More critically, the above-ground growth—the tall flower spikes, broad, sword-shaped leaves (from which it gets its name, from the Latin "gladius" meaning sword), and vibrant blooms—are all potentially vulnerable. While not the most preferred browse, these tender, succulent parts can be attractive to deer, especially in times of scarcity when preferred food sources are limited.
Plants defend themselves against herbivores through physical and chemical means. Gladiolus employs a moderate physical deterrent. Its leaves are generally smooth and lack the sharp spines, thorns, or hairy textures that make plants like barberry or lamb's ear less palatable. However, some gardeners anecdotally report that deer show less interest in certain hybrid varieties with tougher, thicker foliage. Chemically, Gladiolus does not produce significant quantities of the potent toxic or bitter compounds found in highly deer-resistant plants like foxgloves (digitalis) or daffodils (lycorine). It lacks strong aromatic oils that deter deer, such as those found in lavender, sage, or mint. This overall lack of powerful defensive chemistry makes it a possible target for foraging deer.
It is crucial to understand that "deer resistant" is not synonymous with "deer proof." A plant's susceptibility varies greatly with environmental factors. The local deer population density and pressure is a primary factor. In areas with high deer numbers and limited natural forage, deer will consume plants they would otherwise ignore, including Gladiolus. Seasonal hunger plays a significant role; during late fall and winter when food is scarce, deer are far more likely to sample non-preferred plants. The availability of more delectable alternatives in your garden also influences risk. A landscape filled with hostas, daylilies, and roses will be a primary target, potentially drawing attention away from less favored plants like Gladiolus. However, if Gladiolus is the only green thing available, it will almost certainly be eaten.
Given that Gladiolus is not reliably deer resistant, proactive measures are recommended to ensure the survival and blooming of your flowers. The most effective strategy is physical barriers. Installing a tall fence around the entire garden is the ultimate solution. For a more targeted approach, protective cylinders of wire mesh around individual clumps of Gladiolus can prevent deer from accessing the plants. Repellents offer another line of defense. These products, which must be reapplied frequently, especially after rain, work by emitting an odor that deer find offensive (e.g., putrescent egg solids) or a taste they find unpleasant. Finally, employing strategic planting by surrounding your Gladiolus with plants known for high deer resistance can create a protective buffer. Deer tend to avoid strongly aromatic herbs like rosemary, plants with fuzzy leaves like stachys, and toxic plants like euphorbia.
