hollingsworthpeonies.com has lots of pics and good descriptions.

Here is a link that might be useful: hollingsworth peonies

I have the same situation going on in my perennial bed as you: lots of summer/fall perennials and a few shrubs. I've fallen in love with peonies and will be adding them gradually each year. It's almost impossible to advise which peonies to plant. There are sooooo many that are beautiful, so I'll leave that to you.

Hollingsworth Peonies has very honest descriptions about peony varieties. He'll write it into the description if they need staking which is very helpful. There's an award that's given plants that have special attributes and it's called "Landscapers Award" (or something close to that) that's given to peonies that are especially fine plants that have all-around good merit such as robustness, beauty, and don't need to be staked, so you can look for those.

I did plant peonies in a garden 10 or so years ago and made the newbie mistake of choosing plants that were too tall and just flopped all over the place. It was a real chore to stake them up. They were described as 36", but grew taller than that; to at least 42" with bomb-type flower heads. It's almost impossible to find any supports tall enough to hold plants that tall. This time I'm going to chose shorter varieties (28 to 34 inches tall) that are just as beautiful and have descriptions stating "stiff stems" or "no need to stake".

The three peonies I received last fall from Hollingsworth Peonies had HUGE roots and were strong and healthy looking. If you visit their website you'll find lots of colors and varieties to chose from. Take notice of their bloom time: early, early middle, middle, or late if you want various colors to bloom at the same time.

I've decided not to purchase the huge bomb-type peonies as I'd rather not have the added chore of staking them. You'll see how many beautiful double and semi-double plants available that aren't so prone to flopping over. There probably are a some bomb-types that aren't floppers. I'd like to know about them.

There are other growers who sell large rooted peonies. I've seen good things written about those listed below, but no personal experience with them:

songsparrow.com
adpeonies.com and
peonyparadise.com

Thanks for your replies. Looks like a very nice website, one I could browse for days. I still have a few questions.

If I plant my new peonies this fall, will they bloom next year? Maybe I'll get lucky and find some in bloom.

I understand that early, early-middle, etc. refers to succession of bloom times; do I just need to go on that, or can I find out what month that means for my area of the country (Chicagoland), so that I can create perennial plant combinations?

Anything else I should know besides the floppiness issue? I hate to stake plants, but I do put a tomato cage around mine before it leafs out. I might want to move it (again). Best time would be fall?

Finally, can you recommend any with long bloom time? Mine only lasts a few days it seems.