When are hops flowers to be harvested?

I have a hops plant that came up in a container from last year (Total fail last year growing them. I thought it was just too hot.) I put them next to my kids old wooden playset that I had grown some peas on. I trained the new vines up onto the lattice and they have taken off, growing clear to the top of the set and now over the rails. Its very cool and there are lots of hops flowers now.

So when are they "ripe" and what do you do when you pick them?