Debuting golden yellow flowers when many other plants have ceased blooming, popcorn cassia is a welcome addition to the late summer and fall landscape. In cool climates, it is enjoyed as an easy-to-grow annual in containers and in-ground plantings. In Zones 9–11 it is grown as a perennial or multi-stem shrub, reaching an impressive 10 to 15 feet tall and wide.
Popcorn cassia gets its common name from the scent of its foliage. Some folks think that when the leaves are disturbed, the plant gives off the scent of buttered popcorn. Other people find the fragrance less appealing, characterizing it as the scent of a wet dog or mice. No matter the fragrance of the foliage, popcorn cassia is a colorful and welcome addition to both tropical and temperate landscapes.
Planting Popcorn Cassia
In tropical areas, plant popcorn cassia in landscape beds and alongside other shrub plants where it has room to expand. It is a great plant for adding interest to a lackluster corner of the landscape or anchoring an island planting in fall. It is particularly striking when planted alongside banana, elephant's ear, or castor bean and any plants with dark green leaves.
In cool climates, plant popcorn cassia in containers and landscape beds where it will begin blooming when the heat of midsummer sets in, then continue its flower show until the first frost. Amplify its bold yellow flowers by pairing it with orange and magenta dahlias, color-drenched snapdragons, or bright purple verbena bonariensis.
Popcorn Cassia Care
Popcorn cassia is easy to grow as an annual or perennial. In tropical regions, it will form a multi-stem shrub. Staking is helpful in Zones 9–11 where popcorn cassia puts on new growth each year, rarely killed back by freezing temperatures.
Plant popcorn cassia in full sun and rich, moist, well-drained soil. Start it from seed or begin with a purchased rooted cutting. Seeds will germinate more readily when soaked in water for 24 hours. Sow seeds shallowly indoors in February or March and wait until all danger of frost has passed before transferring outdoors.
Provide plants with ample water and fertilize as needed if soil is lean on nutrients. Plants grow quickly and unfurl many new leaves and flower stems in heat and humidity. Expect the plants to slow their growth significantly when temperatures fall below 80 degrees F. Popcorn cassia will tolerate a light frost. In cold regions, it can be overwintered indoors in a greenhouse or a bright window. Bring the plant inside when nighttime temperatures are in the high 30s.
Beware of Invasive Look-Alikes
A member of the Senna genus—Senna pendula var. glabrata—is an invasive plant in South Florida and should not be planted. Senna pendula var. glabrata has the potential to spread to wild areas, displacing native species. When purchasing popcorn cassia, make your purchase from a reputable nursery and carefully inspect the plant tag before buying.