Brassica soil is clay. In regard to organic matter, I beg to differ with my hero farmerdilla. Brassicas don't form mychorrizal associations, and they seem, in my experience, to not differentiate between proper garden soil and new, unimproved soil that is well fertilized (chemically). This has to do, possibly, with their origin as a seaside mediterranean plant, growing in soils that were poor in organic matter. Chard and beets (different species) share the same seaside origin, and they too do not form associations. Fertilizer needs (nitrogen needs really) are approximately proportional to leaf area. They are lower for arugula or turnip, and larger for cabbage and collard. They also like soil on the alkaline side, or at least not the regular acid we have here.

I had to look up the program, to see what the criteria was. There was no way I could see children all across this huge country receiving their plants at the same time, because of the disparity between zones as far as planting seasons...... and expect them all to be ready in September. Reading further, I see that they don't expect that. You just need a photo and measurements. I have never had a cabbage I planted in March grow until September, and if it did......it would be as tough and strong as a hockey puck. Your goal then if you're going for size is just to keep it growing as long as possible. Sadly, you found out what happens to cabbages when they react to a lot of water, especially if it comes after a dry spell. You may be able to just peel back gently that one split layer. If you don't and the leaf starts to die it'll get dry and leathery and could start up a rot on the good layers. I'm not a southern gardener so I really can't speak to how it's done down there. Just about cabbage in general. Have you measured it lately?

I have few cabbage plants. Bought the seedlngs around early May. They are big and forming head. When I look at yours in the picture I can say that it need fertilizer, mostly nitrogen. Another thing about cabbages is that they need MORE water. Also, cabbage being a cool crop will not like very hot day and night. Partial shade is preferred over full sun. I don't know your growing conditions,(temps, sun, shade, watering..) but it looks like your cabbage is getting ready to bolt, as there is no head at all.

Interestingly I am trying to collect them for the same reason too. :) If I remember correctly (I'm still trying to verify this), being aroids, they don't have pods, but form fruits. The fruits, which form at the end of the stalk like a thick cluster of grapes, are bright orange/red when mature. The seeds inside are whitish (again, I need to verify this), and there are a few in each fruit. The fruits should form from those diamond-shaped features on the very immature seed stalk heads. The problem is that they are very much loved by wildlife, and the bright red colour really attracts them. I've also found that many of the immature stalks have been chewed by some very hungry critters. The ones I've seen this year are nowhere near ready yet. I don't know how long their shelf-life is, so I would probably ship the whole berries, rather than taking the seeds out first, which would protect the viability of the seeds more. Make sure you package them in a way that discourages mold and fungi from forming. Good luck. Try asking in the aroid forum too. They should be able to give you better info than I can.