If you have leeks to spare try cutting out the flower stem on a couple of dozen or so .. I did this about this time last year and still ended up with useable leeks for stews and soups over winter but I did have to remove the rest of the defunct stalk .
Some were good enough to use as braised leeks in gravy or white sauce .
Those leeks that we didnt deflower gave me some seeds around June this year .. they are now dried ( airing cupboard in a paper bag for a week ) and stored in some cold oven dried rice in an air tight (small potted meat ) jar, ready for an early start in January 2012.