I'm growing blue sweetcorn in a large crate converted into a planter, which has reached 2-3 feet tall with sturdy side shoots, but no sign of cobs yet.They were planted directly into the crate, in compost & manure, perhaps this is better as there's no need to disturb the roots?
I've planted some mixed salad leaves between them to make full use of the space, they seem to be doing ok.