I am stumped! I think I would try to find out who maintains and plants these flowers and ask.

It's hard to tell on my monitor what color the flowers are but if they were bright pinkish red, it reminds me of red valerian. Does the gray foliage in the lower right belong to the same plant? That is definitely not red valerian.

Looks like one of the Asclepias species (Milkweed), maybe Asclepias incarnata.
Anyone of of the MO native species of Asclepias would be an attractive garden plant, plus, comes with a huge bonus. They are Butterfly magnets!
Check the link below for a photo from Missouri plants website. Click on the BACK link at the bottom of the page to view all of the native Asclepias species.
Rb

Here is a link that might be useful: Asclepias incarnata

As soon as I saw the pic I too thought it looked like a milkweed, but usually has leaves on the stems.

Pam

It does SORTA look like milkweed. Thinking like a tree forum guy here, maybe its a long stem cultivar or something.

This weekend I'm headed to the Botanical Garden. Maybe I'll see something labeled there that resembles it!

I took this SLIGHTLY better pic at MOBOT this sunday. They had it tagged "Asclepias curassavica - Blood-flower" and looking it up on the internet it is indeed a version of milkweed.

Razorback and Pam you all are good!

I've grown that myself and still got it wrong. lol
There are lots of butterfly lovers growing it for Monarchs who like it for a host plant and will visit the flowers too. I've only seen it for sale at a nursery once here and bought a couple. I've grown it from seed also. Someone in the Butterfly Forum sent me seeds. The ones I purchased in pots bloomed a lot better though.

I noticed it got a Plant of Merit award from Mobot.

Here is a link that might be useful: Mobot - Asclepias curassavica

Mystery solved! Thanks for letting us know.

bump for Christie. I bought seeds for this last year. I didn't get them planted and don't know how viable they are but I have seeds if you want some.

I had forgotten about this thread Helen. Thanks for the offer but I have seeds I saved from some I grew about three years ago. They might still be good. I have them set aside to try. I may get low germination.

Monarchs definitely prefer tropical milkweed over asclepias tuberosa (butterfly weed) to lay eggs on. My tropical milkweed got completely defoliated from all the Monarch cats munching on it.