Moles are small mammals that live primarily underground. They dig tunnels and burrows to create an extensive underground network. While moles play an important role in aerating and enriching soil, their tunneling and burrowing behaviors can also cause damage to lawns, gardens, and landscapes. In this article, we will explore the types of damage moles can cause and provide solutions for preventing or repairing mole damage.
Tunneling and Burrowing Damage
The most obvious damage caused by moles is the tunnels and mounds of dirt they leave behind as they create their underground burrows. There are a few types of mole tunnels:
Main tunnels
These are the main underground passages moles use to get around their territory. Main tunnels are wide and very deep, usually 6-12 inches below the surface. You’ll know a main tunnel by the large, obtuse mounds of dirt that are pushed up as the mole digs deeper. Main tunnels are used frequently and can cause significant disruption to the landscape.
Feeder tunnels
Feeder tunnels branch off from the main tunnels. They are more shallow (2-4 inches deep) and meandering as the mole searches for food. Feeder tunnels leave small, rounded piles of dirt behind, almost like miniature volcanoes. The numerous feeder tunnels can make yards look messy and uneven.
Surface tunnels
Surface tunnels are short passages the mole creates just under the grass. They connect deeper tunnels or are used to quickly escape predators. Surface tunnels can yellow and kill grass by separating roots from soil.
Overall, the complex network of tunnels can make lawns bumpy and uneven. The raised tunnels are tripping hazards for homeowners. Walking on tunnels can also cause them to collapse, leading to sunk-in holes or depressions in the yard.
Root Damage
In addition to tunnels, moles burrowing close to plants can damage roots. As they create their shallow feeder tunnels, moles can chew through roots less than 3 inches below ground. Damaged, severed, or exposed roots can lead to plant stress, dieback, and even death. Some of the garden and landscape plants most vulnerable to mole root damage include:
- Flowers – tulips, crocuses, hyacinths
- Vegetables – carrots, potatoes, onions
- Shrubs and bushes – boxwoods, azaleas, rhododendrons
- Trees – Japanese maples, dogwoods, dwarf fruit trees
Young plants are also more susceptible to root damage. The stressed, injured plants have a harder time absorbing water and nutrients, leading to poor health and potential death.
Soil Disturbance
The extensive tunneling can also negatively impact the soil itself in several ways:
Compaction
Tunnel walls get compressed over time, creating hard-packed areas surrounding the tunnels. Plant roots have difficulty growing through heavily compacted soil.
Changed structure
Loosening soil from digging tunnels, plus added compaction, changes the composition of topsoil. It alters the balance of air pockets, soil, water, and organic matter that plants need.
Drainage issues
The maze of tunnels can redirect natural water drainage through a yard. Areas with more tunnels tend to hold more moisture, while places with collapsed tunnels can become drier. These drainage issues create inconsistent growing conditions.
Raised pH
Moles bring subsurface soil to the surface when creating tunnels and mounds. Subsoil often has a higher pH than ideal topsoil. As this gets mixed in, it raises the overall pH, creating alkaline soil conditions. Many plants prefer neutral to acidic soil.
Loss of nutrients
Some nutrients and organic matter get deeper buried into the soil profile as moles dig. This can deplete nutrients in the topsoil essential for healthy plant growth.
The changes moles cause in soil can have long term effects on plant health and ability to thrive. It takes time and amendment to restore ideal growing conditions.
Damage to Structures and Foundations
In some cases, moles may tunnel around or under important structures, causing additional problems:
Undermining foundations
Tunneling too close to buildings or under cement slabs/patios can undermine the stability and shift foundations. This can lead to cracking or sinking.
Pushing up pavement
Tunnels under driveways, sidewalks, or garden paths create raised areas as the ground is pushed up. This creates tripping hazards and uneven walkways.
Chewing electrical wires
Moles searching for food (like earthworms) near underground wiring may damage the protective insulation. This can expose and chew through electrical wires, causing fires or power outages.
Entering pools
Moles sometimes accidentally dig into in-ground pools or hot tubs, causing leaks, drainage, and structural issues.
While less common than landscape damage, structural damage from moles can be very expensive to repair.
Indirect Lawn Damage
In addition to their tunnels, moles do further damage to lawns through:
Drying out
Raised tunnels are pathways for air circulation to dry out soil. Tunnel collapses also leave depressions. These effects reduce moisture in grass.
Change in pH
As discussed for garden soil, bringing subsurface soil to the surface raises lawn pH. Most grasses grow best in slightly acidic soil with a pH of 6-7.
Encouraging weeds
Disturbed soil provides the perfect seedbed for weeds to germinate and take hold. Weeds then compete with grass.
Spreading disease
Moles can carry fungal diseases on their feet or fur. Moving through the soil profile spreads spores that infect grass.
Exposing grass roots
Shallow tunnels expose grass roots to air, causing them to dry out. Exposed roots are also more vulnerable to temperature damage.
Inviting other pests
The tunnels provide easy access for other grass-damaging pests like voles or insects.
Already stressed from tunneling damage, lawns become less resilient and have difficulty recovering from these indirect effects of moles.
Quantifying Mole Damage
It’s difficult to attach a definitive dollar value to mole damage, as costs vary based on:
– Number of moles – More moles equals more tunnels and damage. Mole territories overlap, so damage accumulates.
– Size of yard – Larger landscapes usually sustain more damage as they provide more potential tunneling area.
– Type of landscape – Formal gardens with flowering plants or vegetables suffer more issues than grass-only lawns.
– Value of plants – Damage to older mature trees or expensive landscape plants costs more to replace than common flowers or grasses.
– Structural damage – Tunneling that causes foundation, pool, or patio problems is very costly to repair.
However, looking at estimated costs provides a sense of the bill mole damage can quickly add up to:
- Repairing lawn tunnel damage – $200 – $500
- Fixing plant root damage – $50 – $300 per plant
- Regrading sunk-in tunnels – $300 – $1000
- Replacing damaged plants – $20 per annual, $200 per bush, $300+ per mature tree
- Structural repairs from tunneling – $1000s
Controlling moles before they cause damage is a much more affordable solution.
Regions Where Moles Cause the Most Damage
Moles live in areas throughout the United States. However, they cause the most extensive damage in certain regions where conditions allow populations to thrive.
Northeastern States
The cool, moist climate of the northeastern United States is ideal habitat for eastern moles. States including New York, New Jersey, Pennsylvania, Connecticut, and Massachusetts often have high mole populations. Summers in the northeast also coincide with peak garden planting and growing seasons, increasing potential mole damage.
Midwestern States
The fertile soil and abundant earthworms (a mole delicacy) of the Midwest supports large mole populations. From Illinois, Iowa, and Indiana to Ohio and Michigan, midwestern gardeners and landowners report substantial mole tunnels and damage. Hot, dry summers also worsen drought stress on plants already compromised by mole root damage.
Pacific Northwest
The loose, moist soils and mild temperatures of the Pacific Northwest are welcoming to moles. Northern California, Oregon, and Washington have dense populations of Townsend’s and coast moles. These moles thrive in soil conditions ideal for gardening and agriculture, increasing their pest status in the region.
States Bordering the Mississippi River
The riparian corridor along the Mississippi River provides ideal habitat for eastern moles. Reports of significant mole damage come from states including Louisiana, Arkansas, Missouri, Illinois, Wisconsin, and Minnesota where soils are conducive to tunneling.
Within these regions, damage also increases in areas with naturally loose, deep, fertile soil. River bottoms, lowlands, and drainage plains see more destruction from extensive mole burrowing.
Most Common Mole Species Causing Damage
There are several different mole species in the United States, some more destructive than others. The types doing the most damage include:
Eastern mole
The eastern mole (Scalopus aquaticus) is likely responsible for the majority of mole damage nationwide. They thrive across the eastern half of the country, anywhere from southern Canada to the Gulf Coast that has moist soil and abundant earthworms. Eastern moles are voracious tunnelers capable of causing extensive damage.
Broad-footed mole
The broad-footed mole (Scapanus latimanus) Floridas throughout much of the west coast and seriously impacts gardens and landscapes. It is the most destructive mole in the Pacific Northwest. Broad-footed moles sometimes also swim rivers and streams to reach new territories.
Hairy-tailed mole
Also called the Oregon mole (Parascalops breweri), this species tunnels from the Pacific Coast through the Rocky Mountains. It is common in British Columbia, Washington, Oregon, Idaho, and the northern Rockies. The hairy-tailed mole’s extensive burrowing significantly damages plants.
Townsend mole
Townsend’s mole (Scapanus townsendii) inhabits the coast along northern California and Oregon south to Baja California. It thrives in moist soils and causes substantial damage to crops, gardens, and landscaping. Townsend’s mole is especially problematic for farmers.
Prairie mole
The prairie mole (Scalopus aquaticus machrinus) is a subspecies of the eastern mole found across the Great Plains. It is common from Texas up through the Dakotas. Prairie moles damage lawns, gardens, golf courses, parks, and croplands throughout the plains.
Knowing the type of mole pest allows targeting control methods to specific behaviors and tunneling habits.
Plants Most Vulnerable to Mole Damage
Moles feed primarily on insects, worms, and larvae – not plant roots. However, their tunneling still damages many species of garden and landscape plants. Some of the plants most vulnerable to mole damage include:
| Plant | Type of Mole Damage |
|---|---|
| Tulips | Bulbs damaged by tunneling, roots disturbed |
| Other spring bulbs like daffodils, hyacinths | Root damage, bulbs tossed up on mounds |
| Roses | Shallow root damage, bushes uprooted by tunnels |
| Rhododendrons & azaleas | Shallow roots damaged, prefer acidic soil |
| Boxwoods | Extensive surface root damage |
| Iris | Prefers dry soil, suffers from wet tunnels |
| Vegetable crops – potatoes, carrots, onions | Root chewing and disturbance in grow beds |
| Berry bushes – raspberries, blueberries | Tunneling causes established plants to lean and slump |
| Young trees & saplings | Vulnerable to root damage due to small size |
| Dogwoods & Japanese maples | Shallow root damage |
Gardeners in mole-prone regions should take their plant choices into consideration. Focusing on deeper rooted, drought and disturbance tolerant species can help minimize damage.
When Do Moles Cause the Most Damage?
Moles tunnel and cause issues year round. However, there are certain times of year when their damage is most destructive and noticeable.
Spring
In early spring, moles damage bulbs and roots of emerging flower plants and vegetables. Their tunnels heave up expanding plant shoots trying to reach sunlight. Moles also kill young seedlings by disturbing germinating seeds.
Summer
During hot, dry summer weather, mole tunnels worsen drought stress on gardens, lawns, and landscapes. Plants already struggling suffer more from root loss to tunneling or inability to grow in compacted soil. Stressed plants are also more vulnerable to diseases that may spread via moles.
Fall
As gardeners plant spring bulbs in autumn, mole tunnels wreak havoc chopping and disturbing the tender bulbs. They also tunnel through and damage lawns freshly seeded in fall. Moles continue actively tunneling late into fall since they do not hibernate.
After rains
Moist soil after spring rains or fall downpours stimulates earthworms and insects to move closer to the surface. This prompts increased mole tunneling and damage as they hunt food. More mounds appear post-rain.
Gardeners should be vigilant about minimizing mole damage during these key seasons and conditions. Prevention is most effective when targeted before peak damage periods.
Conclusion
Moles may seem like a nuisance, but they can cause severe and costly damage to gardens, landscaping, and lawns. Their extensive tunnels undermine grass, uproot plants, harm roots, and alter soil. Moles also create tripping hazards and can damage pavement and structures. Some regions with ideal tunneling conditions report chronic and devastating mole damage.
The first step is identifying if moles are present by the telltale mounds, ridges, and collapse sinkholes their tunnels create. Timing controls to prevent damage in spring, fall, and after rains is key. A combination of deterrents, repellents, traps, and exclusion options often works best to control moles and stop further destruction. Though messy and disruptive, moles can be managed to limit the harm they inflict. A mole-free garden and lawn is within reach with persistence.