i've seen hay being used as insulation for plants.

I ave my dozen trees planted in big pots and I make holes in the pots and plant it in a raised bed in the garden. In winter I dig the pots out and take them inside the 3 car garage. Frankly this was a fun job when I had two trees but with dozen trees it became a daunting job.I have a roof over the raised bed and the house covering the west side, I am planning to make a home made green house nothing fancy by closing the north, south and east sides by by greenhouse fabric. The house provide some heat and may be I can provide some heat too. The temperature has to stay under 30 in order for the trees to stay dormant. I have another ambitious idea comes February I will raise the temperature to 45-50for the trees to start blooming in March and have little figs in April. This will extend my figy season by two months I will have no worry about ripening. Off course wife thinks I crazy but that is Ok she will change her mind when she dips her teeth in sweet figs as early as June.