The simplest dog training solution in this case is allocating him an area where he s allowed to dig as much as he pleases. Once this zone s been established, you can make it understood that there is to be absolutely no digging in the rest of the garden, and you can enforce your rules with a clear conscience. As set these boundaries you know your dog now has his own little corner of the world to turn upside down and inside out as he chooses and all parties are happy.
But what if you don t have a "spare corner" of the backyard for your little digger to call his own? What if the whole thing, grass, flowerbeds, and gravel path, is just too dear to your heart? This is ok, there is a solution to this as well. You can invest in a sandbox, which you can place anywhere in the garden.
You can even make one yourself (the deeper, the better, obviously). Fill it with a mixture of sand and earth, and put some leaves or grass on top if you like for effect and get your dog interested in it by having a scratch around yourself, until he gets the idea.
One great dog training tip is to make it clear to him that the sandbox is OK but that everywhere else is a no-dig zone, spend a little time supervising him. When he starts to dig in the box (you can encourage this by shallowly burying a few choice marrowbones in there), praise him energetically and if he starts digging anywhere else, correct him straight away with an extended finger or hand command and state a firm "No!" or "ahh-ah-ahhhh".
Then, redirect him immediately to the sandbox, and dole out vociferous praise when digging recommences.

To really clarify the lesson, give him a treat when digging gets underway in the sandbox the close proximity between the correction (for digging out of the sandbox) and praise/reward (for digging in the sandbox) will ensure that your point strikes home and you will have dog training success.