_gonzo_

I live in S. Florida, when we get cold enough weather to effect a ficus the leaves turn yellow (not black) and drop off within a day, to three days after exposure. This happens even though the temp stays above freezing. However, temps under 40 degrees for just a coulple of days can reduce a ficus to a stick. The upside is that the trees down here take very little time to come back. Many times showing new growth within 2 weeks after warming back up.

Don't shoot the messenger, but I also have a place in Maine. One weekend while I was away we had a frost. One of my older ficus (a healthy tree) turned black and it died.

Keep yours as warm as you can even watering with warm water. The grow light certainly won't hurt either. I wish you luck.

Cheers,

_gonzo_