I like toothlesslady's idea. But you can't wait there with a hose. So what you could do it get a sprinkler and before you go to bed at night turn it on. Point it at the deck so that he cant go on the deck an pee on the garden because he will get all wet.

You could try to find a sprinkler with a timer, if he pees in the morning have the sprinkler going then too. After all the best time to water is at night or in the morning.

Open Eyes