Fig Plant in Unheated Tunnel Greenhouse


I have a some fig plants in pots in a home made unheated tunnel greenhouse. I have a thermometer inside which went down to -4 degrees Celsius.
My greenhouse set up is as follow:
Hoop tunnel with cardboard on the inside covered with plastic then covered with a tarp. The figs are placed directly on cardboard and stacked on each other then covered with blankets.
I know some people keep their fig plants in the garage or sometime dig trenches in the ground and bury them over the winter (not sure what the temperature would be in the trenches) and they survive just fine
So my grand question is to ensure survival should I just bring mine to the garage or just leave them as is and hope for the best?

Note: l went to the greenhouse and out of curiosity clipped off a branch and it was still green inside.





Thank you for contacting Toronto Master Gardeners with your question.

Figs are hardy only to USDA zone 7 (zone 6 for certain varieties), and ideally should be overwintered in a space with temperatures between 0 to 10 degrees Celsius. Given the repeated cold spells we have been experiencing in Toronto this winter, to be safe, you may want to move your fig plants into your garage (if it is above freezing). Then, once the worst of winter is over, you can move them back into the tunnel greenhouse so that they do not break dormancy too early.