It is not possible to stop squirrels from entering a garden. Although there are steps that can be taken to reduce the damage they cause. Additional information on living with grey squirrels can be downloaded from the RSPCA
Netting can give protection to fruits and shrubs when squirrels are showing interest in them. Wire netting is best used for permanent structures such as fruit cages, as squirrels can quite easily bite through plastic.
Netting can be placed over areas where bulbs and corms have been planted, to deter squirrels from digging them up. Alternatively groups of bulbs can be placed inside a planting basket designed for aquatic plants and the top covered with chicken wire. This can be sunk into the ground at the correct depth for the bulbs. Bulbs in pots can be protected with wire netting. Usually once bulbs have started growing, bulbs become less attractive to squirrels and the barriers can be removed.
Various designs of squirrel-proof bird feeders and tables are available from garden centres. These usually enclose the food dispenser in a stout wire cage that allows birds access while excluding squirrels.
Animal repellent substances and scaring devices are likely to give no more than short-term protection.
It is permissible to control grey squirrels by shooting or trapping, provided this is done in a humane manner, but shooting is not often feasible in gardens for legal and safety reasons.
Traps are available from some garden centres or mail order companies. The most widely used is a cage-type trap that will capture squirrels alive. Such traps can be baited with peanuts, they must be checked at least once every 24 hours and preferably morning and evening. Under the Wildlife and Countryside Act it is illegal to release non-indigenous animals into the wild, so any grey squirrels caught should be killed. Methods considered to be within animal welfare law include shooting or allowing the squirrel to escape into a sack, where it can be held while a sharp blow is delivered to its head. Drowning squirrels is not a humane method of dispatching any animal and is illegal.
Unfortunately, more squirrels are likely to move in to occupy the vacated territory, so a garden is unlikely to be squirrel-free for long.
There are no poisons approved for use against grey squirrels in gardens.