From what I can determine this specimen is in the papyrus family.
It does re-seed itself, but not on an invasive level. This medium-small plant can take lots of sun, looks unusual in the garden and I like it!
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On the other hand, this plant has shown itself to be invasive.
My plan this year, is to prune off all the ‘flowers’ so it cannot reseed itself.
I believe it is a sea holly, but, to me, it resembles a thistle.
On a positive note, the deer are not remotely interested in this greenery.
susansflowers 