The sunny yellow flowers of the cup plant (Silphium perfoliatum) look beautiful against a bright blue sky. The sky is the usual backdrop you see when admiring the flowers of this eastern North American native because they top long 8 foot tall stems!
The large leaves that climb the stalks are fused in pairs with the leaf opposite. They embrace the interesting square stalk, giving the impression of the plant stalk perforating the leaves, and form a little cup that captures rain water, thus giving the plant its common name.
I’ve been a bit negligent about providing support for the heavy stalks, and the stems have splayed out from the centre.
The result is a ring of sky-high yellow flowers that dip and swing in a swaying circle.
When I walk by the circle of tall flowers, I am always reminded of a painting by Matisse titled Dance. (Photo Wikipedia)
Recently, while I was sitting in the garden reading, I was tickled to spot this goldfinch taking advantage of the water-capturing quality of the leaves that gives the plant its name. The photo is a bit soft-focus because it was shot through screening.
Willow House Chronicles 
I also have a clump of cup plants. In Kitchener, where we had rich soil, they grew to an incredible height. Here, on thin soil, they usually get to be only 5 feet tall. However, this summer, no doubt because of the regular rain, they are about as tall as yours.
This is also the case for a native sunflower which blooms very late in the season. I think it is Helianthus maximiliani. It was about 8 feet tall in Kitchener. Here it does beautifully (in the sense that the patch has increased a lot over the years) but gets to be only 2 to 3 feet tall (but it does not look as it will be taller this year).
Cup-plant seem to be one of the species which has benefited from the relaxation of roadside mowing in Ontario – it used to be scarce, but now it seems to be, if not everywhere, at least very frequent
Uh-oh, this post looks suspiciously like the one I’ve been planning since yesterday to put up for tomorrow! I don’t suppose we’re long-lost twins or anything? 😀
I planted my first cup plant when I lived in the Adirondacks. Loved the little birds using it for water. Then…tragedy…found out it is considered highly invasive there. Had to rip it out. 😦 But here in MI, it is a native! Woo-hoo! So back into the garden it went!!! Hooray! 🙂
Thanks for teaching how cup plant got its name. Ours aren’t even blooming yet,and only 3feet tall.
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Alain, interesting observations on the effect of soil! I don’t have Max, would like to try it.
Fred, don’t see a lot of it right around here, but noticed it was plentiful out around Belleville way.
Dandy, I’ll be checking in.
Ellen, I’ve never heard of it being an invasive. Glad you are able to reclaim it!
Furry, you need to give them a stern talking-to.