I have been told to harvest the common garlic plant when the tops dry before the flower(that is so pretty) starts to form otherwise your garlic cloves will not keep for very long. This stands to reason I suppose because when the plant flowers it has put all of its reserve energy into that form of reproduction. I have heard that you should reduce the leaves should the plant have too much nitrogen in the soil and go mad
I have just planted (6 weeks ago) half an acre of the stuff -so I hope
I'm right !
Megan