My uncle in Chicago has had a 4-in-1 apple tree for over a decade but it is on it's way out. It is a beautiful tree. All but one of the grafts has failed over the years and it is down to the main apple type which needs cross pollination but no longer has other types available. Sorry, I don't know his specifics but I was thinking of planting one until he gave me a tour of his backyard.

Anyone else have stories about 3-in-one trees, compound fruit trees? Are they just not to be trusted, or, do I need to go with a great online dealer?

Multi-graft fruit trees are very common here and good for folks with restricted space. They are no harder to grow than a single variety tree but they can have issues with graft failures over time, although I know of a number that have been well maintained and all grafts are working and producing well. They are often available in an espaliered form, which makes tending to the individual grafts pretty easy.

I am far more skeptical about the mixed variety or "fruit cocktail" trees. There is a much higher rate of failure on these due to incompatible grafting - I just don't understand the logic behind a cherry, plum, apricot, apple and/or pear all on the same tree for anything other than novelty of it!!.

And of course it does make a difference as to the source.......a multi-graft tree is NOT something I would purchase from a box store but rather from a fruit tree specialist.

gardengal48 thank you! I was think a 3 in 1 apple, or a stone fruit 4 in 1, like apricot, plum, peach and nectarine. I think I should really do my research. I am indeed low on space.

You can always try a 2 or 3 tree planting in a small space to have your varieties in a small area. Look up backyard orchard culture with Dave Wilson Nursery. Its a very popular method in California

https://www.youtube.com/watch?v=u4qpL5pDKd4