I'm going to unearth this thread because it has some interesting info.
I have a 15 gallon pot that is 16" high and 23" across. I am mixing up about 1/2 Pro-Mix and 1/2 pine bark. I will also apply some Espoma TomatoTone.
I have 2 seedlings of Straight Eight in a 4" pot. Suze advised me to cull one seedling rather than trying to separate the two.
Then I will be sowing seeds of Lemon Cucumber and Poona Kheera. I will be placing a 4' x 8' trellis in the pot and hopefully that's enough for 3 plants in a 15 gallon pot.
Advice is always welcome.