Molehills in the Garden: What They Mean and What to Do

Molehills in the garden mean a mole is tunnelling under the lawn and pushing the loose soil from its tunnels up to the surface. Fresh molehills of dark, damp, crumbly soil that appear overnight show that the mole is active now, and a line of hills usually follows a single tunnel. A lawn covered in molehills is often the work of just one or two moles, because moles live alone and defend their own tunnel systems. The realistic choices are to put up with the hills, to have the mole trapped, or to protect small areas with buried mesh, since repellents have little evidence behind them.

What causes molehills in a garden?

Molehills are caused by moles digging and extending their tunnel systems under the ground. A mole feeds mainly on earthworms and soil-living insect larvae that fall into its tunnels, so it keeps digging new tunnels to reach fresh feeding ground. The soil a mole excavates has to go somewhere, and the mole pushes it up through the surface, which is what forms each molehill. Lawns with moist, well-drained soil and plenty of worms are especially attractive to moles, which is why well-kept gardens are so often affected.

How many moles make a garden full of molehills?

A garden full of molehills is usually the work of one or two moles rather than a large number. Moles are solitary animals that each keep their own tunnel system, and a single mole can push up several new molehills in a day. A large number of hills therefore says more about how actively one mole is digging than about how many moles there are. The exception is spring and early summer, when young moles leave the nest to find territories of their own and new activity can appear in gardens that were previously clear.

How can you tell if molehills are fresh?

Fresh molehills are made of dark, damp, loose soil with no grass growing through them, and they appear overnight. Older molehills dry out, turn paler, settle, and gradually grow over with grass or weeds. A simple test is to flatten a molehill or gently press down a raised surface tunnel with your foot, then check the next morning. If the hill has been pushed up again or the tunnel has been raised, the mole is still using that part of the system.

Are molehills harmful?

Molehills are mainly a nuisance rather than a danger, but they do cause real damage to lawns and borders. Tunnelling disturbs grass roots and plants, raised surface runs leave the lawn uneven, and soft ground over tunnels can collapse underfoot, which is a trip hazard. Stones brought up in the soil can damage mower blades if the hills are mown over. Mole tunnels run shallow and rarely threaten the foundations of a house, although long-term tunnelling can undermine paths and patios.

Why do molehills appear at certain times of year?

Molehills tend to appear most noticeably in spring and autumn. In spring, moles extend their tunnels while looking for mates, and later young moles disperse to find their own territories. In autumn, and after heavy rain, changes in where the worms are in the soil lead moles to dig new tunnels, which pushes up fresh hills. Moles do not hibernate, so molehills can appear at any time of year, including mild spells in winter.

Do mole repellents and deterrents work?

Mole repellents and deterrents, including sonic devices, strong-smelling products and home remedies, have little reliable evidence that they remove moles. At best, a deterrent may push the mole into another part of the garden or next door for a while, and the mole can return. Buried wire mesh set vertically around a small bed or a new lawn can protect that particular area, but it is not practical across a whole garden. Reducing heavy watering can make the surface soil less attractive to worms and therefore to moles, but it will not remove a mole that is already there.

What are the legal ways to deal with moles?

Moles are not a protected species in the UK, but any method used to kill them must be lawful and humane. Strychnine, which was once used on moles, was withdrawn in 2006, as recorded in a peer-reviewed study of mole control after the withdrawal. Gassing products for moles do exist, but buying and using them requires a certificate of competence, so they are not a garden DIY option. Trapping in the active tunnel is the usual method, and it targets the mole that is causing the damage rather than other wildlife.

What should you do with the molehills themselves?

Molehills are easiest to deal with once the soil has dried, when it can be raked or brushed out across the lawn rather than flattened into it. Flattening wet molehills with a spade or roller compacts the soil and smothers the grass beneath. Molehill soil is fine and free of weeds, so many gardeners collect it for potting or top-dressing. Sunken areas over collapsed tunnels can be filled with a little topsoil and reseeded once mole activity has stopped.

When is professional mole control worth it?

Professional mole control is worth it when new molehills keep appearing, when the damage is spreading across a lawn you care about, or when you would rather not set traps yourself. GEM Services, a BPCA member, identifies which tunnels are in active use and traps the mole responsible, which usually resolves the problem without affecting other wildlife. Mole problems are not urgent. More detail is on the mole control service page, and the next step is to request a quote.