How do I straighten a tree? I just planted 4 trees with fairly large root balls and two...

I just planted 4 trees with fairly large root balls and two of them hold settled and are no longer straight. How do I fix this?
Can you recommend a border plant?
Answers:    dig 'em up and fix the problems. don't fiddle around... obtain to it. the longer you wait, the more shock to the trees...plus, it's vital that the root flare is not below the soil surface or the tree will 'fail to thrive'. I know it will be greatly of work, but if you want good trees there, in that just isn't a better way to fix it.