Calamagrostis Karl Foerster AGM 5LCalamagrostis acutiflora Karl Foerster (also known as Calamagrostis Stricta) is a slender, upright form of ornamental grass. The dense feathery flowerheads start green, turn to purplish bronze and then fade to the colour of light straw, lasting well into winter. A recipient of the RHS AGM (Award of Garden Merit), for all round excellence in the garden.