LC,
When I was living on Nantucket we had an early freeze and I had to pick quite a few of my tomatoes while they were still green. An old gardener told me to put them in a grocery sack with a couple of ripe red apples. When I asked him why, he replied, "I dunno, it works though. Maybe the apple gives them the idea of what they're really suppose to look like."

Oh, and speaking of apples... That'd be me