A 3 gallon pot is small for a 4 foot tree. I would keep them outside and get only morning sun. Make sure the black pot sees no sun. You don't want these to start growing till transplant time. Bring them in for frost. I have 3 sour orange trees outside now and I bring them in when the temps drop down to the lower 20'sF

Steve

I think you would be ok leaving them outside in the nursery pot until your ready to plant them. Bring them inside the sunroom if temps are going below freezing. I wouldn't worry about the rainwater unless it rains for days straight. I would worry about the wind blowing them over in that small pot so maybe put some bricks or something around the pot so that doesn't happen.

Ike - if you can manage option 2 and have room - do it. But as your collection expands, I think that option 3 becomes most realistic. I do suggest that you do what you can to maximize thermal stability [jugs of water, rocks, cement, etc.] if you leave them outside.

I am in zone 9b and have 40+ citrus trees in the ground and 100+ in pots - various sizes. I do not use fast draining potting mix - no! I do not worry about overwatering. I have damaged trees by letting they dry out and so do worry about underwatering. Although low 20's [F] is rare in my area, I will only move the larger pots into a shed when temps are to dip to low 20s or teens. The smaller 4x4 pots get whisked in / out of a shed as possible when temps are to dip below 32.

I must admit that many of the pots are strategically placed against a fence or on patio flagstone / cement slab - and i have many pots full of rocks nested against some of them - for (wind stability as well as) thermal stability.

Can you set the pots in part shade and fill in around the pots with lots of pine mulch, like up to the rims? This should stabilize the temps in the pots and keep the rootballs from freezing. Get ready to throw a big frost cloth over them in extremely cold weather events. As long as they are not sitting in a low spot, they shouldn't be bothered by the rain.

I would do option 3. I have several trees in pots and rain in the winter is not a problem. In fact on trees that have leaves you will need to water occasionally, like once a month. Rains do not provide as much moisture to pots at you would think. Best way to tell if they need watering is to lift the pot. If heavy, do not water. If easy to lift, go ahead and water. If temperatures are going to be below 29-30 degrees bring inside or at least beside the south side of house. I would put trees in sun since you are bringing in during cold temperatures. If you get a growth flush just bring inside if temperatures are going below freezing.