The sudden appearance of raised ridges and conical mounds of soil across a manicured lawn is the most frustrating sign of a mole’s presence. Moles are common subterranean pests, and their digging activity immediately raises the homeowner’s concern: will the grass die? Moles do not consume grass, but the extensive network of tunnels they create causes severe, indirect damage to the turf’s structure and root system. Understanding the mole’s behavior and the precise mechanism of this damage is the first step toward effective lawn recovery. This analysis explains how a mole’s search for food translates into turf destruction and outlines the steps necessary to restore a damaged lawn.
Understanding Mole Tunneling Behavior
A mole’s life is spent almost entirely underground, and its constant tunneling is driven by an enormous appetite for invertebrates. Moles are insectivores that feed primarily on earthworms, beetle larvae, and grubs, often consuming up to their own body weight in prey daily. They construct two distinct types of tunnels, each serving a different purpose and creating different types of lawn damage.
The most visible sign of activity is the presence of surface runs, which are temporary feeding tunnels created just beneath the grass layer, typically only one to three inches deep. These shallow runs appear as the characteristic raised ridges that snake across the lawn as the mole pushes up the topsoil while hunting. Moles can excavate these shallow tunnels rapidly, sometimes creating over 100 feet of new run in a single day.
The second type is the deep run, which serves as the main highway and permanent residence, often located six to twelve inches or more below the surface. Soil excavated from these deeper tunnels is pushed up to the surface, forming the volcano-shaped piles known as molehills. These deeper tunnels connect feeding areas to nesting chambers, but it is the shallow, temporary feeding runs that cause the majority of the surface disruption.
How Mole Activity Affects Grass Roots
Moles rarely kill grass outright because they do not eat vegetation; the damage to the lawn is a side effect of their search for food. The primary mechanism of grass death occurs in the shallow surface runs, where tunnel construction physically severs the grass roots from the deeper soil. This separation prevents the grass from accessing moisture and nutrients, causing the turf to yellow or turn brown in the affected area.
The creation of air pockets is another significant factor in root damage, particularly in the surface runs. When the mole pushes the soil upward to form the ridge, it introduces large voids beneath the turf layer, separating the roots from the surrounding soil. This exposure to air causes the roots to dry out (desiccation), which quickly leads to dead patches of grass along the tunnel path.
The conical molehills, which are mounds of displaced soil from the deeper tunnels, can smother the grass directly underneath them. While the damage from a single molehill is localized, extensive tunneling can lead to numerous mounds, creating patches of dead turf that require repair. The resulting uneven surface also makes the lawn difficult to mow and creates issues with water distribution, further stressing the grass.
Restoring Your Lawn After Mole Damage
Restoring a lawn after mole activity involves repairing the physical damage to the soil structure to allow the grass roots to re-establish contact with the earth. The most immediate step is to collapse the raised surface tunnels and compact the soil back into place. This can be accomplished by lightly pressing down on the ridges with your foot or using a lawn roller, which eliminates the damaging air pockets and reconnects the severed roots with the soil below.
For molehills, the soil should be carefully raked out and spread thinly across the surrounding lawn, or collected and removed entirely. Once the tunnels are flattened and the surface is level, any bare patches of dead or thinned grass should be overseeded with new grass seed. Applying a thin layer of topsoil or compost over the seed ensures good seed-to-soil contact, necessary for germination and successful recovery.
Long-term recovery depends on addressing the underlying reason the moles came to the area: the food source. Moles will continue to tunnel in areas with abundant earthworms or grubs, so reducing the population of these prey items serves as a preventative measure against future damage. Proper watering and fertilization of the recovering areas will help the new grass take hold, allowing the lawn to return to its previous condition within a few weeks.