Cats like to explore their surroundings, and fences and walls cannot prevent this. For them, roaming freely through the garden is the most species-appropriate behaviour imaginable. Essentially, what they need is to monitor their turf regularly, to mount expeditions and above all to act out their natural urges and instincts.  

If you want to prevent your cat from going beyond the boundaries of your own garden (e.g. because of a particularly dangerous road), a special cat fence can help. This might be made of a material your cat will not be able to scale (e.g. plastic or Plexiglas) or it might have an extension at the top that skews back inwards (also made of plastic or similar), making it harder for a cat to climb over. In any event, a cat fence definitely has to be very high. Trees, or other plants cats can climb up, should never be planted around the borders of your garden. If you already have a tree there, the solution is to fix a fairly wide plastic shield around the trunk to stop the cat climbing up it.

Unlike dogs, cats cannot be trained not to do their business in your vegetable bed or flower bed; to them, the loose earth pretty much constitutes an invitation. Here, it helps to mulch the soil with natural materials with long fibres, such as dry bark mulch or chopped twigs.

Vegetable beds can be protected by bordering them with plants which have a scent disagreeable to cats – Balkan cranesbill, for example, or common rue or wormwood. Not all animals will react to the same plants, so it is best to find out first by trial and error what will deter your cat.