I grow my leeks in two three batches, one April, one late May, one June, a short row of five different varieties. That way I get a staggered harvest, I can fill gaps where I've harvested or the plant has failed, and have some seedlings to put in spare areas such as where some of my blighted potatoes were harvested earlier than I anticipated.
This was the raised bed with leeks at different stages in late July...
I've planted out some of the 'Jaune Gros De Poitou' from Thomas Etty seeds (supposed to grow up to 5'!) only a couple of weeks ago......not planned that late but the ground wasn't free until then.... :-\