Globe Artichokes

I ate  one or two long ago, and remember quite liking them, so thought I'd try my hand. Bought as seedlings:

There's an interesting variation in leaf shapes, but it's hard to tell if these mean anything.

Update 2015/10/11:

Nearly a month's growth. I'm starting to get concerned about the size implications...

Update 2015/11/15:

Trimming off base leaves after wind damage seems to have helped.

Update 2015/11/22:

Update 2015/11/27:

Heads starting to form.

Update 2015/11/30:

Multiple heads showing on one plant. A big one, then two smaller.

Lesson learned is that three plants in one tyre is too many. One becomes dominant and shades the others, stunting them somewhat. Maybe in a bigger tyre?

Update 2015/12/03:

Tiny, but tasty. About the size of a golf ball, but I was afraid they'd open as flowers. I suppose they'll get larger.

Update 2016/01/28:

I've been picking them while they're too small. Will know better next time.

Update 2016/03/13:

New leaves growing from crowns.