The Tree of 40 Fruit is an ongoing series of hybridized fruit trees by contemporary artist Sam Van Aken. Each unique Tree of 40 Fruit grows over forty different types of stone fruit including peaches, plums, apricots, nectarines, cherries, and almonds.


Here is a link to the project's page...
http://www.treeof40fruit.com/

How very unusual,.

I tried a plum with several varieties grafted onto one stock tree.
It did not make it through our winter.

My dad tried those fruit trees - a 5-way apple, and a 3-way cherry, and I've tried a couple of mixed citrus as well. Either, as Caroline says they die off altogether, or one type that is the most vigorous of all the fruits takes over the whole tree. Pretty soon you have only one type of fruit anyway. I had lemon/orange/grapefruit on one tree and it looked great for the first year. After its first winter, the grapefruit grew tremendously and the other two died right out.

So, yes, I'd agree it's a nice idea but I have serious doubts you'd ever get one to mature with more than one type of fruit still producing.

It works best when you graft the tree yourself, this way you know where all your graft unions are and you don't prune out a particular variety. Like Elaine said the more vigorous varieties will be dominant so pruning is very important. Places like burgess, direct gardening, and other low cost nurseries sell crap trees that are often not even grafted but seedling plants so beware of purchasing mulitgrafted plants from these folks. some things to keep in mind when buying or grafting your trees is only plants in the same genus can be grafted to each other. Apples and plums won't graft to each other but you can do things like pecans and hickories on 1 tree because they are both in the Carya genus. Stone fruits are the most common because "most" all prunus members are compatible especial on a rootstock like saint Julian. You can grow peaches, plums, nectarines, apricots, almonds, pluerries, pluots, apriums, and other interspecific prunus hybrids all on the same tree and this is how the Mr. Aken has success in doing a 40 on 1 tree.
Any woody plant can be grafted including things like roses. So anyone that had the wish to do so could make a 40 in 1 rose bush as well or any other plant with multiple varieties in the same genus.