Laidback Gardener Tip of the Day

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A Plant that Repels Cats and Dogs?

décembre 13Sometimes you’ll see plants that are that are supposed repel cats and dogs and keep them out of the garden due to their repulsive smell. This is an interesting concept because sometimes our furry friends do cause damage in the garden, but… do these plants really work?

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Plectranthus caninus

A plant that is sometimes offered as a cat- or dog-repellent is so-called Coleus canina, which is sold under various trade names such as Scardy Cat™, Piss off-Plant™, Dog’s Gone™ or Bunnies Gone™. This is actually Plectranthus caninus and it’s supposed keep dogs, cats and other mammals (raccoons, rabbits, etc.) at bay. One seller even invented a pedigree for this plant, claiming that it is a hybrid obtained by an Australian amateur gardener by crossing a plectranthus with a coleus, although, in fact, Plectranthus caninus has been growing wild in Africa and India for millennia. Moreover, when one seller tried to get a patent for this plant (under the name ‘SUMCOL 01’), his request was denied on the grounds that “the plant presented no discernible difference from the species”.

Despite its unpleasant odor, released when you or the animal touches the plant’s sticky foliage, there is no evidence that cats, dogs or other animals are in the least disturbed by the presence of Plectranthus caninus. My late cat Geisha used to like to sleep in its pot and my dog Maggie simply ignores it.

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Rue (Ruta graveolens)

However, there is rue (Ruta graveolens) that apparently repels cats (but not dogs or other mammals). It seems that it is effective in some cases and not in others, depending on the cat’s sensitivity. The problem is that rue often causes burns to humans, as it gives off phototoxic furocoumarins. By phototoxic, I mean that burns only appear when the skin is first exposed to the plant and then to the sun. When the sun is not present, such as in the evening or on cloudy days, there is no unpleasant reaction. Moreover, rue is used as a medicinal plant and even a condiment in some countries, although it should be used very sparingly, since it can cause gastric problems or even death if consumed in important quantities.

The repellent effect of rue is however very limited, covering only about 6 to 12 inches (15-30 cm). To protect a garden from cats, assuming your local cats are sensitive ones, you’ll need to literally surround the bed with rue plants.

Rue is a short-lived perennial, lasting 4 or 5 years, and is hardy in zones 4 to 9. Before planting rue, check to see if it can be legally grown in your area, as it is banned as a noxious weed in some countries.

To learn how to effectively keep cats out of the garden, see the Tip of the day of 14 November 2014.

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