Whatweed, I am still leaning toward rattlesnake master since the leave have spiny edges and the blooms are in cluster mostly on the plant top. It also know as Button snakeroot, Since I can’t see the second plant you mentioned. I assume you meant : ‘American bur reed (Sparganium americanum)’. Its round shape feathery flowers are up and down along the stem. leaves have smooth edges. Its seed head are dark green, and it does look similar to the Rattlesnake master. You have an amazing plants laboratory at your beckon call. 200 known and counting….Thanks to your posting, also get to see them too. Best wishes!

Laura, today I found a common buttonbush just a few feet from the rattlesnake master. I had never seen either plant before. The fruit sure remind me of the other.

Thanks Laura. I wasn’t fully convinced until I found good pic of leaves. I have identified approximately 200 plants on my place, many with help from you all. I have no idea how many more there are. This spring was the wettest I’ve ever seen. I see a lot of plants that I don’t know.

Maybe rattlesnake master (Eryngium yuccifolium). https://en.wikipedia.org/wiki/Eryngium_yuccifolium