This topic comes up a lot on various forums here at Gardenweb.

Check out the linked thread below, especially the posts near the end of the thread. There are photos of one person's solution. The garden mesh mentioned in this thread works pretty well and is non-toxic. Chicken wire also works, but shows through the mulch a little more easily.

Here is a link that might be useful: Cat Thread From Garden Clinic

thank you for the help.i am willing to try anything that does not harm him.

Installing plastic forks stuck into the ground with the tongs slightly, sticking up has been suggested, in previous postings. It is reported that the cats stay away from such treated beds and are smart enough not to injur themselves while learning to avoid those garden or landscape beds.

I have pine trees with the really long stickery needles, and use those for mulch. My cat doesn't like them at all and won't tread on them.

Susan

Another good reason to always wear gloves when gardening. Even if it's not your cat, no telling what comes along when you aren't looking. I saw my neighbor pulling weeds up from around her mailbox the other day without gloves. The same mailbox that every dog in the neighborhood signs his name to when taken on "walkies" by their masters.

Pine cones, the more stickery the better. Makes a pretty mulch and the cats don't dig. You can rake them out when you want to work the beds. They last quite a while.