Do cat repellents work? How to stop a cat from using garden as litterbox? Tell me how to keep cats out of my garden. These are common questions of concern to all gardeners but is there a real answer?

The first line of defence is to ensure that your yard boundaries are secure. Any gaps in your fence should be blocked to deny low level access. But cats can jump so fix a taut wire or string some six inches above the top of your fence to deter this approach.

Once inside your garden many people say that the best cat repellent is a dog who will soon see off any feline invader. If you are not a dog lover then you will have to resort to more passive methods. Since cats like to lie on freshly dug soil you should lay mulch on your borders so that no bare soil is left exposed. Seed beds should be covered with wire netting or twigs arranged as a barrier.

Young trees should have plastic guards fitted around their trunks to protect them against use as a scratching pole. Your garden pond should be covered with netting to keep your fish safe.

Cats are generally known to dislike water so a well aimed bucketful or a squirt with the hose will certainly make an intruder run. After one or two dousings it may learn the lesson and stay away.

To protect plants and borders both mothballs and citrus are said to be effective deterrents. Place the mothballs, orange peel or lemon rind in the borders. Alternatively spray cloths with orange scented air freshener and place the cloths around the plants you wish to protect. Other known cat repellents are cayenne pepper, coffee grounds, pipe tobacco, lavender oil, lemon grass oil, citronella oil, eucalyptus oil and mustard oil.

Certain herbs are said to deter cats. In particular rue but not catmint which has the opposite effect. Coleus canina is another plant which is marketed by one merchant as a cat repellent.

The broadcaster Jerry Baker has suggested treating your yard with a tonic made from chewing tobacco, urine, birth control pills, mouthwash, molasses, detergent and beer. A smallholder has reported success using dried rabbit blood but you may feel that the ingredients listed in the previous paragraph should be tried first.

If you visit your local garden center or hardware store you will find several cat repellent products on sale. These range from electric water sprinklers and ultrasonic devices to sprays and granules.

Motion activated sprinklers act in the same way as a burglar alarm using an infra red detector. When the cat enters the area covered by the detector the sprinkler shoots out a jet of water to scare the animal away. It is claimed that, after one or two encounters with the jet, the cat will learn to avoid the area.

Ultrasonic devices emit a high frequency sound which is annoying to cats (and dogs) but is not audible to humans. There are various different models some of which operate continuously and others which have an infra red detector and only emit a pulse of sound when the cat triggers the device. To be successful you need to ensure that the model is powerful enough to cover the area you wish to protect. In addition make sure that the sound frequency is designed for larger animals since some models are intended to deter insects and so would be no use for cats.

There are also commercial scent cat repellents. Those that use chemicals should be kept away from any food crops but the essential oil based granule varieties act in the same way as orange and lemon peel mentioned above. Another way to keep a cat out if the garden is a repellent evaporator which consists of a container holding puffed rice which has been impregnated with essential oils. These are effective for three to four weeks and can then be refilled for a further period. Another natural product which many people claim really keeps a cat out of the garden is lion's dung. You may need to visit your local zoo to obtain this although some stores do stock zoo poo.

In Ontario, Canada the local township provides a cat trap service. Once the animal enters the cage it cannot escape but is completely unharmed. The owner has to pay to recover his pet and so should be encouraged not to let the cat stray in future. Apparently few owners bother to reclaim their cats but just obtain another kitten. However this sounds like a good way of dealing with a cat that cannot be deterred by any other method. If there is no such scheme in your area, just buy your own trap.

So, to recap, the first priority is to secure your boundary fences. Then you have the whole selection of suggested cat repellents ranging from homemade recipes to expensive commercial gadgets. I would suggest that you try the orange peel and prickly twigs for a start. If you are around when the intruder appears, try the bucket of water or hose. Even if you miss, the shock may be a sufficient deterrent. If these do not do the trick, then you may have to consider the commercial alternatives.

Hugh Harris-Evans is the owner of The Garden Supplies Advisor where you will find further articles, gardening tips and product reviews.