Yes, squirrels frequently target iris bulbs. This is a common source of frustration for gardeners, especially during the autumn planting season when rodents are focused on foraging and caching food for winter. The fresh, loosened soil around newly planted bulbs acts as a clear signal to passing squirrels that an item has recently been buried there. Whether the squirrel intends to eat the bulb or simply use the disturbed area to bury one of its own nuts, the resulting damage can destroy the planting.
Why Squirrels Target Iris Bulbs (And Which Parts They Eat)
Squirrels are driven by instinct to forage for high-carbohydrate food sources to sustain them through colder months. Bulbs are compact energy packets, containing starches and sugars that appeal to small mammals. While some bulbs, like daffodils, contain toxic compounds that deter consumption, iris bulbs and rhizomes are not reliably unpalatable to all squirrels.
The actual damage often involves more digging than direct consumption. Squirrels unearth the bulb to inspect it, sometimes taking exploratory bites before discarding it. This digging alone is enough to severely damage or kill the plant by exposing it to the air, breaking its roots, or moving it. The main part they may consume is the fleshy storage tissue, which provides a concentrated source of calories.
How to Identify Squirrel vs. Vole Damage
Determining the specific culprit is the first step toward effective pest control, as the signs left by squirrels and voles differ significantly. Squirrel damage is typically a messy, above-ground affair resulting from their digging action. Look for shallow, small holes roughly the size of a quarter or half-dollar, often with the bulb completely dug up, partially eaten, and left lying on the soil surface.
Vole damage, conversely, is characterized by a clean disappearance of the bulb, which is consumed entirely from below the surface. Voles are burrowing rodents that attack the bulb underground, meaning a gardener may only notice that a plant failed to emerge in spring. Above-ground signs of voles include small, one- to two-inch wide runway paths in the grass or mulch, or small, open entrance holes to their tunnel systems.
If an unearthed bulb shows small, parallel grooves from tiny incisor teeth, it is likely the work of a vole or mouse. A squirrel’s bite marks are generally larger and more haphazard.
Physical and Scent-Based Deterrents for Bulb Protection
Protecting iris bulbs requires a dual approach using physical barriers and sensory deterrents to discourage digging. Physical exclusion is the most reliable method for newly planted bulbs that are most vulnerable. Gardeners can create underground cages using half-inch hardware cloth, burying the bulbs inside the wire mesh before covering them with soil.
For larger planting areas, chicken wire or hardware cloth can be laid flat over the planted soil and secured with garden staples. This barrier allows iris shoots to grow through the openings but prevents squirrels from digging down to the bulb. The wire should remain in place until the ground freezes solid or until the spring shoots are several inches high.
Scent-based repellents work by appealing to the squirrel’s powerful sense of smell, making the planting area unattractive. Dusting the newly planted soil surface with granular deterrents like cayenne pepper, crushed red pepper flakes, or commercially available capsaicin sprays can discourage a curious squirrel. These materials cause mild irritation when sniffed or tasted, prompting the animal to seek food elsewhere. However, these applications typically require reapplication after rain or watering to maintain their effectiveness.