There is no species, no name and no other information except for that the cabbage can grow to 40 pounds. I have 5 gallon buckets and I want to put them in them instead of the ground. Is a 5 gallon bucket going to be big enough for one cabbage? Do they need lots of nutrients and care or will they be good in a heavy compost based soil?
Plant them in the soil !! If they get that big they are going to need more than a five gallon bucket will hold as far as nutrients !! That is a huge cabbage !!!
How about a 24x24 short raised bed that sits on nutrient rich compost mixed soil? I want to keep the slugs away and the sow/pill bugs because I can go out and find 100 of each in less than hour here. I figures even the slightest riased bed will help to help keep the bugs out.
I bet they brought home Megaton hybrid cabbage seeds. It's known for the big heads of cabbage it produces. Try a search on that to get info. Even if it's not exactly that one, you should get some information to help you.