A tall Star of Bethleem with large, pyramidal inflorescences of white flowers in late summer/fall.
I find it given as a syn. with O. narbonense L., which is a different species, so there is clearly confusion about this species in the trade.
Looking great at the edge of the woodland garden.
Images: O. arcuatum
Germination: try at warm first and if it doesn’t germinate switch to cold.