It depends on the species and the effect you're going for. I suggest you'd regret more planting them too close than you would planting them too far. I wouldn't plant a large tree closer than 15' or 20'. It's not that much when you picture the grown up tree.

If by tulip tree you mean Liriodendron tulipifera, 10' is far too close. This will get to be a very large tree - 60-90 feet tall and with a canopy spread of as much as 50'.

And a great many trees wll produce a lot of suface roots as they mature which can easily lift or crack paving - maples, cherries, sweet gums, magnolias, many types of oaks, black locust and most conifers.

Tulip poplar is the largest growing eastern North American deciduous hardwood, you are talking about planting an eventually monumental tree in that spot. Unless you plant a dwarf cultivar, at least one of which has been named - but may not be on the market at this time.

Well I moved it over a bit today and took a couple more pictures. It's at about 17 feet in this picture. I'm thinking that's probably a safer distance. Hopefully it'll still cast some good shade on the driveway in the coming years.

Seeing it, I would add 3' more and round it to 20'. There is NO question that the tree will cover and shade the drive. But you want its contribution to the space to feel more like a cathedral than a mobile home.

Point well taken. As you can see it's about maximizing the shade on the drive way. There's obviously plenty of space for such a large specimen in this lawn.

It is of course going to take many years for this planting to produce much of a shadow - for a long time it's not going to be big enough, to be followed eventually (decades from now) by a phase where it may be thought to be rather overbearing.

Or just plant it close to the driveway so you get some shade on it sooner and by the time it becomes a real problem we'll all be dead

It can cost thousands to pay a fully certified and insured tree service to safely remove a large tree.

Embothrium has just about convinced me to rethink this as a driveway tree altogether. I carried it over to a spot where a white pine blew over this winter. and took some pictures of what it might look like there. This is a spot that can easily accommodate a gigantic tree. It's also much further from the house so safe removal for any future home owner might be a little less of an issue.

The biggest negative to this planting location is that it's close to a part of the yard that can be pretty wet during the spring.

I may give some additional thought to whether this should be a driveway tree of if I'll go with something smaller for that application. There are a number of these tulip tree's utilized as driveway trees in our area. At their current size they make great shade trees, but I still may rethink that application.

I hope you never planted that tulip poplar… wish I knew more about trees before moving into a mini forest of them….