Thai Giant Crown of Thorns Queen Millionaire has some of the largest flowers on any euphorbia, often reaching 2 across or more. The blossoms are orangey-red with creamy white petal edges, and the flowers appear in clusters during the spring and summer blooming season. In China, its believed that when a euphorbia produces 8 flowers in a cluster, good luck will grace the household. Crown of Thorns are indestructible houseplants that thrive on neglect. Be sure to let the soil dry out between waterings. Grow Queen Millionaire on a sunny windowsill, or outside during the warm summer months.