Miscanthus sinensis (Chinese silvergrass) -- there are loads of cultivars out there, and this tall grass can be found in MANY gardens, possibly including yours!
Personally, I've just never liked these things. They always seemed so out of place in American gardens to me.
This grass originates in Asia and has been used in the US as an ornamental plant since the 1800's. It has now spread into disturbed sites throughout the Eastern US, Colorado, and California. It displaces native vegetation and is particularly flammable. I have seen it growing wild along the highway here in SCPA.
If you have some miscanthus to remove, digging it out usually doesn't work as it is so difficult to remove all of the rhizomes. DCNR recommends using an herbicide. Until you are able to remove it, cut it back before it sets seed each year.
Sources: @padcnr , Invasive Plants Atlas
PHOTO: pisauikan on Pixabay