How do I get rid of termites from a garden bed?

I have a garden bed elevated surrounded by bricks. It has been infested with termites for some years now. Last year, I put down termite pellets and sprayed poison on the places where they mostly were. It didn't solve the problem and they ate and destroyed a rosebush. There are many "treatments" for termites in the garden store, but which one is best and what is the best meathod to eliminate them from my garden and from ever coming back?

View this post on my blog: http://madeinhome.info/how-do-i-get-rid-of-termites-from-a-garden-bed