use a tool similar to this to poke a hole in the gopher trail:
http://www.atgstores.com/garden-hand-too...
then get poison grain from the hardware store. use disposable gloves and put the grain through the hole. it'll drop down into the tunnel directly in the gopher's path and they'll eat it and die. i always found a little rock to put over the top of the hole just to make sure no birds would be able to get to the grain.
you don't have to buy this tool, just use something that has a point like it does. do NOT use a shovel, you'll just collapse the tunnel and the dirt will block the way and the gopher won't be able to get to the bait.
I used to live in Minnesota known as The Gopher State. We had traps like these shown in this link: http://www.trapgopher.com/ They are a specialized trap for gophers. They are tricky to set and place but not TOO hard, hence the video. My friend had a lot of them and successfully trapped them this way any time they arrived on his property. Good luck. They are troublesome and nasty but not impossible.
find someone with a cat and ask for the used kitty liter. Pour it down the gophers hole and in your garden. Bye-bye gophers.
by leaving food out, that will distract it from the garden and don't put the food near the garden.
A gopher is causing havoc in my flower garden. How can I get rid of this pest?