Cats are infamous for being smart, sneaky and athletic. All these skills make them experts at getting into places they are not supposed to be. Repellent can be used to keep cats out of gardens and away from forbidden house areas, but homemade recipes in the past have centred on using cayenne pepper and mothballs, both of which can be harmful to cats. It is reassuring to know that newer creative repellents can be just as effective.
Because cats are finicky creatures, they can sometimes be deterred from a garden by purely physical means. For instance, cats don't like walking on chicken wire, so the material can be laid horizontally over the soil's surface. Then, when it is time to plant, use wire cutters to make holes where needed. Spiky surfaces are also discouraging to cats. If the area is small, consider vertically inserting a wooden skewer in the dirt every few inches. For larger areas, cover the ground with clippings of thorny branches such as raspberries or bougainvillea. Stone mulch is a sharp surface that will keep cats away from the plants it surrounds because they cannot dig in it. Finally, is also possible to scare cats away with visual stimuli that play with the light such as half-filled water bottles or old CDs strung together.
Water is a proven cat deterrent. If personally supervising your own cats, you can alter their behaviour by spraying them with a water pistol when they enter forbidden areas or jump on the counter. In the yard, try running sprinklers at the times when neighbourhood cats are most active. You may choose to invest in motion-sensor sprayers triggered by the cat's motion.
It is possible to incorporate cat repellent into the garden itself with plants like the "Scaredy Cat Plant." Cats hate the odour of it but the tiny blue flowers are pleasing on the eye. It can grow in almost any soil and should be planted 1 to 2 yards apart to create an effective barrier. Other plant solutions include rue (which has pretty, blue leaves), lavender (which also repels deer), and pennyroyal.
While cayenne pepper and mothballs are dangerous, there are many other safe household products that help keep cats away. Used coffee grounds can be sprinkled around plants to repel not only cats but bugs and other pests. If you use blood meal for fertiliser, it can also be spread as a cat repellent. Pieces of citrus can be cut up and spread around the garden or citrus peel can be sowed into sachets for use in the house. Essential oils can also be used inside. Mixes of lemon oil, eucalyptus oil, liquid soap and vinegar have all proven successful at protecting furniture.
You can buy products made specifically to repel cats. For instance, organic repellents made from predictor urine elicit a fear response and keep the cat away. Ultrasonic devices emit a frequency of sound which humans can't hear but which cats detest. These devices can be expensive, but effective, last resorts.