you could dig a hole down and see how far down you have to dig before you hit water and plus if its good soil put it back in and its nice and loose for you, that what im doing, I have the same problem, look at some maps like on google and look at the satalite image it may surprise u how your town looks from above, you can also get a bucket and plant it in that then hang it way up in a tree, but u have to make sure its not goin to fall down.