The best way is to remove them and take them inside or bury them in soil.
Barring that, you may need to wrap them in hot-compost doughnuts, or worse,
electric heaters...depending on what you are planting in them.
Good Luck.

--
Mike LaMana, MS
Heartwood Consulting Services, LLC
Toms River, NJ
www.HeartwoodConsulting.net



"Paulo" wrote in message
. ..
I am planning to place some big pots (20" x20" approx) in my balcony with
some perennials. I am wonder, what is the best way to protect them during
winter time? I was thinking wrapping them with some cloth.... Any idea? I
am
in Toronto, and if i am not wrong it is Zone 5/6
Thanks

--
Paulo