Grown as an annual in northern zones, Popcorn Cassia is a perennial legume from Africa that makes a colorful ornamental plant in the summer and fall gardens. The green compound leaves are covered with fine hairs and flower spikes rise about a foot above the foliage. Each unopened bud has a dark covering and the bright yellow flowers open progressively from the bottom of the inflorescence upward. After the flowers have passed, brown seed pods form. Grow in full sun with ample water and fertilizer. When the leaves are rubbed, it smells like buttered popcorn!