Like to Try Piss-Off Plant to Repel Cat But Can't Afford to Buy Each Year

I live in Orillia, Ontario. I have a problem with a cat using my garden as a litter box and then my dog goes in there and eats the deposit the cat leaves. What could I use to stop this. Would Piss Off Plant work and my garden is 50 feet long how many plants can I use? I read in the question and answer that the Piss Off Plant can be brought indoors but is it OK to prune it right down and I would probably need more room then I have for all the plants I would need. Orillia is very cold in the winter and I am sure the plant would not servive it. I am retired and do not have the money to be buying these plants every year.

The Piss-Off plant is not hardy so you would have to replant every spring. However it is easy to overwinter indoors. You can prune the plants back to help squeeze them into tight indoor spaces. You only need to bring in a few plants because you can take cuttings to produce enough young plants to cover your garden in spring. You would take cuttings in late March or early April for mid-May planting. You need a plant every 4-5 feet, so if you are garden is narrow and 50 feet long, you need 10-12 plants.
Please note that the plant doesn't always work; some cats and dogs are not repelled by it. There is no way of knowing for sure without trying.