Over on Jeannine Blogs, Jeannine Hall Gailey talks about, and asks about, writing poems in a series.
This is a favorite subject of mine, and here is the response that I posted:
Thanks for bringing this up. (I sent my essay on it in to P&W, although that's a long shot.)
I've realized that most of my poems that I'm working on right now are thematic but not actually a series (no necessary ordering). And right now I'm having trouble finding a solid rhythm in any of my projects, which is uncomfortable for me. Even when I'm coming up with some intriguing one-off ideas, it's still uncomfortable.
For fitting those one-offs into a collection, I've heard a few ideas to try: Find the thread that holds them together (chances are there is some overarching abstract idea that each of these poems is expressing in a different way). Then you can retitle the poems to fit your theme, or you can divide the poems into sections and use the section titles to bring in the theme. Okay, I'm out of ideas for now.
Finally, I proposed a session on writing poems in a series to Winter Wheat, and the response was positive. So this is even more on my mind than usual.