I can't say that this method would work for sure in your case, but you can try.
You should make a little cuts in the young tree's bark (optimum length of cuts is around 3-5cm (or around 1.2-2 inches) - depending on the diameter of the tree), almost vertically little above its base with some sharp knife, three or four cuts should be enough.
Then under those cuts in the base of the young tree you make horizontal cut in the bark, and peal some bark so you form a ring around the base where the hardwood part of the tree is without bark. Optimum wideness for the ring is around 0.5cm (or around 0.2 inches), the ring should not be wider than 1cm (or around 0.4 inches).
When you did that, you have to put some dirt/soil around that shoot, possibly mixed with some nice manure (preferably cow's), and water it. From time to time you should add some more dirt around the shoot, so the cuts stay under it at least 5cm (or around 2 inches), off course, water it daily if the weather is dry.
What you are doing, is that you are forcing a young shoot to form a tissue known as callus, and from it to form a new roots, at same time using a bigger roots of the older tree for supplying with water and some of the mineral and nutritional substances.
This procedure lasts one season, and at the end of it you should have a new plant ready for planting. You cut it off from bigger tree under the newly formed roots, and that's it.
I have done this with root plants/pads for getting new plants for grafting apples on them. I hope this procedure helps you. Good luck.
