Charles, I agree with Rhys, the book is slightly vague on the sowing technique for sweetcorn. However, I made the assumption that it would be indoor sown, as it seems only carrots and parsnip cannot be raised indoors in modules.
I raised sweetcorn this year in 2 inch (5cm) modules on 17th April, they are now averaging 6 inch (15cm) in height, at what stage would these be planted out? Additionally, is there still time to sow more indoors in modules or direct?