I've been picking leeks for ages now and they're nearly all gone. They have been an excellent crop. I'm always banging on about the best crops are the ones you can harvest over a long period and leeks are one of these. I started picking when they are young and sweet, between finger to thumb thickness, (I think this is when they're at their best and cooked whole), and continued until they were nice and fat. Here are some young ones just picked and then trimmed ready for cooking.
Remember the white tubes I used to blanch the stems. It worked! The one on the left of the board didn't have a tube and here's another comparsion below. Also below is one of the later picked fat ones.
