Welcome to the critter world. For several years I battled the very same problem with gophers in east Texas. A couple times I actually got rid of all my gophers, but every one of my neighbors had them, so I could not clear the area.
I have watched gophers dig directly under my young castor plants and push them up on top of their tunnel. I have let castor plants grow "wild" for multiple years in places and had as many gophers there as everywhere else. I hooked up my mower's exhaust to tunnels, put juicy fruit gum in tunnels, put gopher bait in tunnels, trapped and killed many many of them, shot many of them with a gun, poured bleach into tunnels, put propane in tunnels and ignited it, and even talked ugly to them. All in vain. Your pitchfork might be the best option if you can't keep a cat.
