Answer: Basically, the weeping top is grafted onto a normal trunk, this joins two separate plants together so they grow as one. You would not be able to mix different genus of apple, cherry and dogwood although you may be able to mix species within the genus. Generally speaking you would need to graft an apple scion onto an apple rootstock, a cherry onto a cherry, and a dogwood onto a dogwood.
There are different methods of grafting. The following web site has more detailed information. (You may need to cut and paste the complete url into your browser ot make it work correctly.)
If you are interested in grafting, the best way to learn is to have someone who knows how to do it explain it and show you how and help you figure out the best method and time of year for the tree you want to work on. Good luck with your project!
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