A fast-growing, underground fruit economy is spreading in cities across America. Some years ago, a young, hippyish couple knocked on my front door. They had noticed that I had fig trees in the yard, laden with summer fruit. If I wasn’t going to pick them all, they asked, could they harvest some figs? Since I was about to take a trip, I said: Sure, have at ’em. Upon my return, as I stood at the door fumbling for my keys, I looked down — and there were two jars of delicious fig jam awaiting me. A little common neighborliness can be deeply enriching, in so many ways. I remembered my happy fig exchange recently when I read that a fast-growing, underground fruit economy is spreading in cities across America. Well, the movement is underground, but, naturally, the fruit is above ground and — like my figs — in plain sight. …