Ivy does not chemically lure rats, but the dense growth it creates offers a prime environment for them to thrive, making it a significant harborage concern. The plant provides exceptional shelter and a safe, concealed travel network for rodents already present in the area. Ivy’s year-round evergreen nature maintains this protective cover even through winter, a time when other vegetation has died back. This transforms the landscape plant into a potential rat habitat, particularly where natural cover is limited.
The Appeal of Dense Foliage for Rodents
Dense, low-lying plant cover, such as English Ivy (Hedera helix), satisfies the rats’ need for secure harborage. The thick, intertwining vines and leaves create a heavy, dark mat that insulates against temperature extremes, providing a stable microclimate for nesting. This dense foliage acts as an effective shield from predators, allowing rats to move and nest with confidence.
The ground cover also provides protected travel routes, often called “runways,” allowing rats to commute unseen between their nests and available food or water sources. When ivy climbs vertical structures like fences or walls, it extends this safe travel corridor, granting rodents access to upper stories and rooflines. This is particularly relevant for the agile roof rat (Rattus rattus). These conditions facilitate the establishment of a rodent population by offering a superior alternative to exposed ground for burrowing and nesting.
Identifying Rat Activity Within Ground Cover
Homeowners can detect rat activity within dense ground cover by looking for several observable signs. The most definitive sign is the presence of established runways, which are smooth, worn paths pushed through the dense undergrowth. These runways connect the ivy to a food source or structure and often follow the base of walls or edges of fences, where rats feel safer.
The discovery of rat droppings within or near the ivy is another clear indicator. Fresh droppings are dark and moist, while older ones appear gray and dry, and they are typically concentrated along runways or near feeding areas. Rats also leave distinct gnawing marks on nearby materials, such as wood siding, plastic utility lines, or irrigation pipes. In cases of severe infestation, a strong, musky, ammonia-like odor, caused by concentrated rat urine, may be noticeable near the ivy, especially when the cover is disturbed.
Reducing Ivy’s Harborage Potential
The most effective method for reducing the risk of rodent harborage involves modifying the ivy’s structure to eliminate the protective cover it provides. Instead of blanket ground cover, the ivy can be rigorously trimmed, or “skirted.” This involves cutting and removing the growth so that the remaining foliage is elevated 12 to 18 inches above the soil. This exposed gap removes the concealed layer rats rely on, making the area less appealing for nesting and travel.
For ivy growing against structures, cutting the vines at chest height and removing the bottom section creates a gap. This prevents rats from using the plant as a vertical ladder to access roofs or upper windows. A more permanent solution is the complete removal of the ivy, replacing it with a low-growing ground cover that does not form a dense, deep mat.
If complete removal is not feasible, homeowners should create a buffer zone around the foundation of the home. This inspection strip is typically a 12-inch to 36-inch wide area of bare earth or gravel immediately adjacent to the structure. This eliminates the dense vegetation rats use for cover and burrowing near the building’s entry points.
Additional Harborage Reduction Steps
Other steps can be taken to reduce adjacent harborage:
- Seal any holes or gaps in the foundation, especially those larger than a quarter-inch.
- Use rodent-proof materials like quarter-inch hardware cloth or concrete to prevent direct access into the home.
- Stack firewood or lumber at least 18 inches off the ground.
- Ensure stacked materials are kept 12 inches away from walls.