Wow, well winter is here. Yes you can leave them in pots. But you are going to need to protect them somewhat. An unheated garage is best. Three in a pot is way too crowed. Mine in pots are in 30 gallon pots for one plant. HUGE pots!
Sounds though like you have a smaller cultivar, as mine will grow to 6 feet high. Still three in a pot is too crowded. Protect it from freezing and thawing, this will kill it. Keep it moist, not wet, not dry. Protect from constant rain.
If you must leave them on the patio, I would put chicken wire or hardware cloth around the pot and fill with leaves covering the plant. Do this after freezing weather to keep it frozen, to keep it from thawing in the sun.Go to the Orchard forum for advice on fruit. It is a lot more active.