The best way to repel cats or deter them from entering your yard is through an integrated approach. This means using combination control methods, such as physical barriers together with chemicals or plants that are repellent to cats. Cats can be a nuisance if they don't belong to you, especially if they are feral. These cats can be noisy at night, dig up garden beds to use as toilets, destroy the bird population and can bring unwanted fleas into your yard.
Cats mark their territory by releasing pheromones, which they rub onto objects. Scent glands are located on their feet and cheeks. When cats want to demonstrate ownership of an area, they spray urine to warn other cats that this space has been taken. It is mostly male cats that have not been neutered that exhibit this behaviour. Cat repellents won't be effective until you have removed scents that have been left behind by territorial cats. Remove any cat faeces as they also have a scent that can mark territory. Wash and scrub any walls or objects in the yard that have been sprayed before applying cat repelling products.
There are a variety of products on the market that can be purchased online or in garden or pet stores. Some use coyote or fox urine to keep cats away. Shake Away Domestic Cat Deterrent is such a product, which is in powder form. The formula claims to repel cats 5 feet on either side of where it has been sprinkled. Havahart has a cat repellent that contains the essential oil of mustard and chillies as well as lemon. Other repellents use the oil of orange, citronella and Bergamot as well as lemon grass. These are sold in liquid form in spray bottles.
Rue is an herb that gives off a very strong odour that cats do not like. Plant this herb in the garden and near places where the cat may be gaining access to your yard. Make your own cat repellent using natural ingredients. Many of the home remedies used to repel cats depend on the cat's sharp sense of smell and its dislike for certain smells. Citrus peels and cayenne pepper are among the ingredients that cats don't like. Cutting raw onions in half and rubbing the juice on an area or sprinkling vinegar are other natural cat repellents that you can try.
There are several devices available that use water as a method for repelling cats. Cats are not fond of getting wet, and water-spraying devices use motion detectors that are activated when a cat-sized animal walks by. The device is hooked up to a garden hose and delivers a sudden, strong spray of water over the area. The cat is startled and gets wet. After triggering the device a few times, it learns to avoid the area. You can move the device to maintain the element of surprise and the hope is that soon the invading cat will realise that there is no safe place in your yard.