The volumes of the "gallon" can be smaller depending on how much they are filled. A gallon pot is a no 1 blow mold nursery pot. If I am limited on space I up pot to the no. 2 pots which is commonly referred to as a 2 gallon pot. I can keep the smaller peppers in that size for a long time as long as it gets water and fertilizer.
https://www.sprigsandtwigs.net/docs/ask/133.pdf
https://www.nurserysupplies.com/traditio ... assic-line
I use mostly the no 1, no 2, and egg cans. I use 6 inch pots for some herbs and I will sometimes wire them for hanging baskets. For big plants like tomatoes, large long lived peppers, eggplant, and citrus trees I like to use a 14 inch pot minimum but an 18 gallon pot is preferred. I use rope handle muck buckets for the 18 gallon pots. They do get brittle after about 3-4 years but will last if you don't try to move them. I usually break them with my pick trying to get the soil out. I do have a couple of 25 gallon tree pots that I bought from a local nursery. I use one of them for edible ginger. The other, I haven't planted yet. I picked up some large resin pots from Costco and I haven't decided what to put in them either, but it will probably be a rose, citrus, or the persimmon. Pots are not as thick as they used to be so I will have to kill a couple of the citrus trees that have broken out. They did not break out as easily from the thicker older pots.
- luckily no air travel or borders to cross; but they'll be outdoors, and cooler, for a couple of weeks - any concerns about that or bringing them back to the hot greenhouse? We've taken plants on vacation before - young tomatoes - when tenting but camping days are over as of last year. This time we'll be in a cottage which will be both nicer and not so nice 
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