Before I got my allotment last year I used to grow many vegetables in containers in my garden. Most things did really well including, to my surprise, sweetcorn. Once I got my allotment I started using toilet roll inners to start off seeds before planting out. My sweetcorn was rubbish last year and is none existent this year. The only thing I can put it down to is starting the seed off in toilet roll inners. The seedlings seem to lose their green colour as they grow before planting out and this is why I'm putting it down to this, they didn't lost their colour when I used plant pots. I don't have any problem with germination though, so next year I'm going to start the seeds off in plant pots as I did when growing in containers and see if this makes a difference.