Hi Colin,
I’ve had the same thoughts, and come to the conclusion that the calendar reflects Charles’ personal work scheme. As a market gardener he needs a lot of plants and properly split them into several batches in order not to have a zillion plants to be sowed, pricked, transplanted and harvested at the same time.
I only sow a particular vegetable the first time it it mentioned in the calendar for the first crop. This is my first season as a ‘Charles Dowding follower’ and my challenge will be to work out from Charles’ calendar if a subsequent sowing recommendation represents the second (autumn/winter) crop, or is one of several first batches.
Does this make sense?
Regards
Erik