This grower is sure of this plant identification.
Miscanthus sinensis 'Kleine Silberspinne', up to 1,2m tall. I have 5 of those, pot sizes vary but at least 3 litres.
Maiden grass, Eulalia
Miscanthus genus (Maiden grass). This genus consists of tall-growing ornamental grasses, they are highly desirable herbaceous plants, which are deal in a perennial border or by the edge of water.
They will prefer full sun with moderately fertile, moist but well-drained soil.