The highly popular Stiff Coreopsis (Coreopsis palmata) sports bright yellow flowers during the dog days of mid-summer. The underground rhizomes spread and form a dense mat, making it excellent for stabilizing dry, sunny slopes and even sand dunes! A perfect match for the most difficult dry soils. Other common names include Tickseed, Prairie Coreopsis and Stiff Tickseed. Hardy to Zones 3 - 8.