Calamagrostis x acutiflora  'Karl Foerster' Feather Reed Grass Size: 3 to 5' high and 2 to 3' wide. Hardiness: Zones 4 to 9. Heat Zones: 9 to 1. Habit: Forms dense clumps of arching, bright green leaves from which rise stiffly upright stalks of feathery flowers. Culture: Full Sun to light shade.