Symptoms

Heaps of excavated soil are thrown up on the surface of lawns and flower beds; tunnelling through the soil disturbs the roots of seedlings and other small plants in flower beds and vegetable plots.

Cause

Moles are rarely seen as these blackish-brown mammals live mostly underground. They dig out a system of tunnels and chambers, and dispose of the excavated soil by throwing up molehills. Apart from the spring breeding season, moles lead largely solitary lives, so all the activity in a small garden could be due to a single animal.

Moles feed on earthworms and other soil-dwelling creatures, not on plant roots. The damage they cause is incidental to their lifestyle. Molehills on lawns must be removed before mowing and collapsed surface tunnels need filling in to maintain a level lawn surface.

Control

Several steps can be taken to control moles or encourage them to move elsewhere:

Mole traps are inexpensive and available from garden centres and hardware stores. They are humane but need careful placement in a tunnel, but not directly under a molehill. The secret is to open up a tunnel with the minimum of disturbance and align the trap with the direction and depth of the tunnel. No bait is required. Handle the trap with gloves as moles are sensitive to human scent. Once the trap is set, gently cover it with an upturned bucket to exclude light and draughts. Check the trap daily. With a bit of luck, the mole will be caught but sometimes the mole pushes soil into the trap. If this happens, clear the tunnel of soil and reset the trap. If this continues to occur, reset the trap in a different part of the tunnel system. Vacant tunnel systems may be taken over by another mole from nearby areas so further trapping may be needed to keep a garden mole free.

Electronic devices are more costly and available from garden centres and mail order firms. Their buzzing noise is said to drive the mole away; however it may only be to another part of the garden.

Caper spurge, the biennial Euphorbia lathyris, has its adherents who claim the root exudates repel moles. It is worth a try, but remove most of the flower heads before seeding occurs or a weed problem may result.

Mole smokes are no longer on sale to amateur gardeners. Professional contractors can be employed to use pellets that emit toxic gases into the tunnel system. This can be effective but freedom from moles may not last long if there are other infested areas nearby from which moles can soon recolonise the garden.