Espalier

I was struck by the beauty of this espaliered pear at the Cloisters.

And I thought someone could really do something with these on rooftops and terraces, where there are ugly bulkheads and mechanical installations to hide. Most fruit trees do decently in containers provided they have an irrigation system; there is plenty of sun and moving air to keep down the leaf diseases; and since roof gardens are isolated from other plants, pests are less of a problem. So it's conceivable one could grow unblemished fruit without having to spray.

Of course, the trees would need to be knowledgeably pruned lest they lose their form, but one could learn. And the more difficult initial training could be handled by the esteemed Henry Leuthardt of Long Island.

http://www.henryleuthardtnurseries.com/

I notice they list apricots, which I've never seemed espaliered.