Moles

What you are looking at

Conical heaps of fine loose soil pushed up onto the lawn overnight, with no visible hole in any of them. Between the heaps, a line of raised turf where a tunnel has been driven along just under the surface, cracked along the top and giving underfoot when you step on it.

In a bed the sign is different. A row of seedlings tilted over, or a small plant wilting for no reason, with the soil beneath it loose and hollow.

The heaps come in runs, often several in a line, and they usually appear in late winter or early spring. That is one animal working, not a colony. Moles are solitary and hold a territory against each other, so a lawn that looks overrun is generally the work of a single mole extending its tunnels.

It has not touched your plants

A mole eats earthworms, and after that leatherjackets, chafer grubs, beetle larvae and anything else that falls into its tunnels. The tunnel system is a trap rather than a route: worms drop into it, the mole patrols and collects them, and it stores surplus worms alive in a chamber with their heads bitten off so they cannot crawl away. It has the teeth of an insectivore and it cannot digest plant material.

So the damage moles do is mechanical. Heaps on a lawn spoil the surface and blunt the mower blades. A shallow run under a seed row heaves the plants and opens air pockets around their roots, which dries them out. Both are real and neither is the mole eating anything of yours.

There is an upside on the balance sheet. Molehill soil is subsoil brought up, worked over and left in a loose heap with no weed seed in it, and gardeners collected it for potting compost long before anyone sold potting compost. Take the heaps away with a shovel rather than raking them flat, since spreading them over the turf smothers the grass and gives you bare patches instead.

The animal that is eating your bulbs

Almost every account of moles destroying a crop turns out to be a vole.

Voles move into mole runs and use them as a ready-made tunnel network, and unlike the mole they are rodents with a rodent’s appetite. They eat bulbs, tubers, roots and the bark at the base of young trees, and they do it in quantity. The mole made the tunnel and the vole did the damage, and the mole gets trapped for it.

The tells are clear once you know to look. Voles leave neat round holes about 4 cm across opening at the surface, which moles do not, since a mole hardly ever breaks the surface deliberately. Damage shows as gnawing, with tooth marks on a bulb or a strip of bark cleanly removed near ground level. And voles leave small green-brown droppings in the runs.

If bulbs are going missing, deal with the vole. Trapping the mole will not stop it, and taking the mole out leaves the tunnel system to whatever moves in next.

What works, and what the law says

Exclusion is the only measure that reliably keeps a mole out of a piece of ground, and it has to be installed before the turf goes down. Mole mesh under a new lawn, or across the base of a raised bed, stops the heaps coming up while leaving the animal free below. Retrofitting it means lifting the lawn.

Trapping works and is a skilled job. In Great Britain a spring trap used for moles has to be one approved under the Spring Traps Approval Order, set properly in an active tunnel, and the Wild Mammals (Protection) Act 1996 makes causing unnecessary suffering an offence. Germany gives the mole full legal protection and killing one there is illegal. Rules elsewhere vary and are worth checking rather than assuming.

Gassing is for trained operators only. Aluminium phosphide releases phosphine, which is lethal to people, and the improvised versions involving exhaust pipes or petrol are dangerous, useless and in most places an offence.

Everything else on sale is folklore. Ultrasonic stakes, windmills, mothballs, buried bottles and chilli powder have no evidence behind them, and the best any of them manages is to move the animal to the other end of the garden.

What to do about it

Work out whether the mole is doing anything worse than making heaps.

Shovel the molehills up and keep the soil for potting rather than raking it into the lawn.

Tread or roll the raised runs back down and water afterwards to settle the roots.

Check for vole holes, gnawed bulbs and stripped bark before blaming the mole for eating anything.

Lay mole mesh under a new lawn or a raised bed at the time you build it.

Expect the activity to peak in late winter and to be one animal.

Leave trapping to someone competent, and check what your own law allows first.

Use no gas, no poison and none of the devices sold as deterrents.

What it gets mistaken for

Voles use mole tunnels and eat roots, bulbs and bark. Neat 4 cm holes at the surface and tooth marks on a bulb are the tells.

Birds and badgers digging for leatherjackets and chafer grubs tear the turf up and scatter it, and the grass comes away because the roots have been eaten.

Rabbits scrape shallow bare hollows, graze growth off at a clean angle and leave pellets.

Ants throw up fine soil around a nest in dry summer weather, in a low spreading mound rather than a conical heap, with ants in it.

Worm casts are small squiggles of soil on the surface in mild damp weather, a few centimetres across rather than a heap, and they are the work of the animal the mole is hunting.