Sedum 'Autumn Joy' Sedum Size: 18 to 24" high and 18 to 24" wide. Hardiness: Zones 3 to 9. Heat Zones: 9 to 1. Habit: The thick stems of this hybrid carry broad, gray-green leaves. By late summer, the tops of the stems are totally hidden by huge, 6-inch cauliflower-shaped clusters of densely packed, pale whitish green flower buds that turn bright pink then deep red from late summer to late fall. Culture: Full Sun to light shade.