ROYAL PURPLE QUEEN Iochroma cyaneum is a member of the Solanaceae family, similar to Brugmansia and Datura, a mini angel trumpet that is sure to please, since this plant starts blooming at 12 inches and never stops. Thats right. Heat and humidity don't phase this garden performer. Royal Purple Queen develops into a medium size plant with a shrub-like appearance. It can reach 3 feet in a single season. In mild climates, it may reach 5 feet tall. It is also fairly wide, reaching 24 to 48 inches. produces clusters of 3- to 4-inch-long, dark purple flowers all summer in mass, with 20 to 30 flowers per cluster. We consider it a truely one-of-a-kind Plant. perennial Cold hardy to zone 6.