Matt wanted me to put in this link to an article I sent him on overwintering trees "Touchy" to my zone 5 NE Ohio. After 26 years in bonsai this is working out fine. This was part of an article in ABS Journal on overwintering in various zones around USA.
http://wiki.bonsaitalk.com/index.ph...ng_Hardy_Bonsai
A couple extra notes:
You can get a nice and CHEAP indoor/outdoor digital thermo from Radio Shack .
I use a 1500W electric heater hanging from roof support of unheated greenhouse to ASSIST when temps got to below zero and, mainly, in early spring when stuff starts leafing in greenhouse after some nice days THEN we get a heavy frost. The heater will bring up the temp a few degrees.
I'm going to try to attach a couple photos of my TROPICAL tree setup indoors in basement with light racks. They spend 6 months per year there!!
and
my outside greenhouse
Regards,
Dale