Spring-flowering bulbs like the crocus are a welcome sign of the season, often pushing colorful blooms through the last patches of snow. They signal the end of winter, but their early appearance also coincides with a period of low food availability for many garden pests. Gardeners frequently face the challenge of protecting these delicate plants from hungry wildlife. While the primary concern often centers on large herbivores such as deer, the greatest threats are frequently smaller, less obvious mammals. Understanding the specific feeding habits of these various animals is the first step in successful bulb cultivation.
The Specifics of Crocus and Deer
Crocus are generally considered low-preference plants for deer, meaning they are not a primary food source, but they are not entirely deer-proof. The foliage and flowers contain compounds that are unpalatable to deer, which tend to seek out less bitter and more nutritious forage. This low palatability is why they are often grouped in “deer-resistant” planting lists, unlike highly desirable bulbs such as tulips.
Deer are opportunistic feeders, and their aversion to crocus is a matter of preference, not absolute resistance. When natural food sources are severely depleted, especially in late winter and early spring, a hungry deer will consume almost any vegetation, including crocus blooms and leaves. This is when gardeners most often report damage, as the early emergence of the plant makes it one of the only available items on the menu.
The resistance of true crocus species (Crocus spp.) is often confused with the high toxicity of the related Colchicum autumnale, commonly called “autumn crocus” or “meadow saffron.” While the latter contains the highly toxic alkaloid colchicine, true spring and fall blooming crocuses do not. Their relative safety from deer browsing is simply due to their bitter taste and texture, which makes them a last resort for grazing animals.
Addressing Other Mammalian Pests
The most destructive pests for crocus bulbs are typically not deer, but smaller rodents that attack the plant from above and below the soil line. Squirrels and chipmunks are notorious “diggers” who are attracted to the newly disturbed soil and the scent of the planted corms. They physically excavate the bulbs, often carrying them away to consume, leaving behind small, conical holes in the garden bed.
Voles, on the other hand, are “burrowers” that pose a threat by eating the corms underground, often in their entirety. These mouse-like rodents create extensive tunnel systems, accessing the bulbs from beneath the soil surface without leaving much evidence above ground until the plant fails to emerge in spring. Vole damage is frequently mistaken for a bulb that simply failed to grow, as the telltale sign is an empty planting cavity.
Rabbits are another common pest, similar to deer in that they tend to feed on the emerging foliage and flowers rather than the subterranean corms. They use sharp incisors to make clean cuts on stems and leaves close to the ground, which can quickly decimate an emerging crocus patch. Identifying the specific pest is important, as protection methods that deter a digging squirrel are ineffective against a tunneling vole or a grazing rabbit.
Effective Protection Methods for Bulbs and Blooms
The most reliable strategy for protecting crocus is implementing physical barriers during the autumn planting season. Since rodents are highly attracted to the corms, surrounding the bulbs with half-inch mesh hardware cloth creates an effective defense. This material can be formed into a bulb cage to protect against both digging squirrels and tunneling voles, allowing the roots and shoots to pass through the mesh while keeping the corm secure.
Planting depth and soil composition also play a significant role in deterrence for subterranean pests. Crocus corms should be buried at a depth of two to three times their height. Mixing sharp grit, crushed oyster shells, or small gravel into the planting hole can deter voles and squirrels from chewing or burrowing. Removing all bulb papery debris after planting is also important, as the scent of the sheaths can attract hungry animals.
For above-ground protection against deer and rabbits, repellents that contain putrescent egg solids or capsaicin are highly effective. These products work by smell or taste, but they must be reapplied frequently, especially after rain or heavy dew. Strategic companion planting with toxic or strongly scented bulbs, such as daffodils (Narcissus) or ornamental onions (Allium), can also help disguise the appealing scent of the crocus.