I live in Pittsburgh, PA. I have a tree that grows with huge leaves each year but never sets fruit. My girlfriend has a tree especially developed for this climate but has the same problem, lots of huge leaves but no fruit. She heels her tree in each year; I do not. A friend in eastern Washington State where the winters are equally harsh gets abundant fig production and does not heel in. My friend said when she lived in Florida they threw their wood ashes on their fig and it also produced well. We were wondering if it might be the acidic soil in Pittsburgh which hinders production. I understand the soil west of the Rockies is more base, which would also result if wood ashes were added.
To determine what your soil really needs you should have a soil test preformed.
Here are links that should help you.