Your fridge.

For
me, in N.Y., once night temps get and stay 35-40 F. I remove my Sarrs
from the pots, dunk and clean the roots in rainwater. Put them in zip
lock bags, spray a little sulphur based fungicide on them and put
into the bottom of my fridge. Works great.

For
VFTs, I drain off excess water from the pots, hit them with a sulphur
based fungicide and place in zip lock bags and pop them in the fridge
for 3-4 months. Late winter around March I take them out and place
in a south and west window until night time temps. Regularly stay
above freezing then slowly acclimate them to full outdoor Sun.