Meet the columnar apple trees. I learned about these when my father started buying them and planting them in big pots - filling up my sister's driveway (gardeners will always find a way). These trees grow to about 10 feet in height but are only 2-3 feet in diameter. Perfect for a tiny garden or even to grow in a pot.
The tree on the left was new last year but is doing well so far. The middle tree has been with me for about 6-8 years and in this location for one. Just to prove these trees have fruit, I've included a picture of some small apples on the larger tree. Not only will these trees give us fruit, then will grow just enough above the fence to provide extra privacy.
Want to know more about columnar apples? Here are some links for you.
Fine Gardening Columnar Apple Trees for Suburban Yards
Burpee. This link is for the Columnar Northpole apple - that's what the young tree on the left is in the pictures above. If you decide you want to order some columnar trees, do it early. They sell out early. If you look around, you'll also find other columnar fruit trees (peaches, cherries, plums, figs).
A couple extra notes. (1) In the middle picture there's a nice piece of dolomite in the front left quarter. It is a nice example of "elephant-skin weathering" that we often see on dolomite; (2) The larger columnar apple had one apple. Once. I was so looking forward to picking it but it disappeared one night during trick-or-treat. I guess I got the trick instead of the treat that year.