Moles are small, subterranean mammals whose intense tunneling habits often lead to noticeable damage in yards and gardens. These creatures are insectivores, primarily searching for earthworms, grubs, and other soil invertebrates, which drives their constant digging activity. While they do not consume plant material, the extensive tunnel systems they create directly impact the health and appearance of turf and garden beds. Understanding the specific nature of this damage helps homeowners address the problem and protect their cultivated spaces.
Surface Disruption: Mounds and Ridges
Mole activity is recognized by two distinct types of surface structures: mole mounds and surface ridges. These structures are the visual evidence of the animal moving soil in search of food and shelter. The presence of these formations can quickly ruin the uniform appearance of a lawn or garden area.
Mole mounds, commonly referred to as molehills, result from the animal excavating deeper tunnels, nests, or main travel lanes. They appear as volcano-shaped piles of loose soil pushed up to the surface, typically ranging from two to twelve inches high. The appearance of multiple molehills spaced apart usually signifies the presence of a deep, permanent tunnel system beneath the surface.
The second type of surface damage is the raised surface ridge or runway, evidence of the mole foraging just beneath the turf layer. These ridges are shallow tunnels that look like raised, winding lines snaking across the lawn as the mole searches for food. These tunnels may be used only once or become part of a frequently used hunting route, giving the turf a bumpy, uneven appearance. The formation of these ridges makes a smooth lawn feel spongy or soft when walked upon, as the soil has been separated from the grass roots.
Impact on Turf and Gardens
Beyond the aesthetic ruin caused by mounds and ridges, the mole’s tunneling directly compromises the biological health of plants and turf. Although moles are not herbivores and do not eat roots, their constant movement through the soil causes significant indirect damage to vegetation. This disruption can lead to patches of dead grass and wilting plants that appear to be suffering from drought stress.
The shallow foraging tunnels cause root shearing and desiccation, which occurs when the tunnel separates the fine root systems of turfgrass from the surrounding soil. When the roots lose contact with the soil, they can no longer absorb water and nutrients, causing the grass above to rapidly dry out and die. This results in the classic dead or brown patches that often appear suddenly across an otherwise healthy lawn.
In garden beds, the problem is more pronounced, as tunneling beneath planted areas can uproot seedlings or disrupt the delicate root structures of established plants. The displacement of soil around a plant’s base can leave air pockets, making the root system unstable and prone to drying out. This instability is particularly damaging to perennial flowers, bulbs, and vegetable plants, which require firm soil contact to thrive.
Mole activity affects the soil structure by bringing subsoil to the surface when creating mounds, which alters the composition of the topsoil in localized areas. While tunneling provides some aeration, the destabilization of the soil layers makes the ground more susceptible to erosion, especially after heavy rainfall. The loose, disturbed soil also provides a perfect medium for weed seeds to germinate, further degrading the health of the lawn.
Secondary and Safety Hazards
The extensive network of tunnels and mounds introduces several secondary problems beyond plant health and visual damage. These consequences include safety concerns and the infiltration of more destructive pests. The uneven surfaces created by ridges and molehills can pose a tripping hazard for people walking across the lawn.
Uneven ground amplifies risk during routine maintenance, as the mounds interfere with lawn care equipment. Mowing over a molehill can dull or damage mower blades, and aerators or other machinery are negatively affected by the soft, unstable terrain. The presence of these subterranean pathways also invites other animals to use them for destructive purposes.
Abandoned or existing mole tunnels provide easy access for other pests, most notably voles and mice. Voles, unlike moles, are herbivores that actively feed on plant roots, bulbs, and bark, causing consumption damage often mistakenly attributed to the mole. By creating the initial underground highway, the mole enables these root-eating rodents to move freely beneath the garden and damage plants without exposing themselves above ground.