Richard C. Bogren, Owings, Allen D.
News Release Distributed 07/31/15
By Allen Owings
LSU AgCenter horticulturist
HAMMOND, La. – We are still a couple months away from fall, but there are several plants to consider now that will be showstoppers come October.
One of the popular fall-flowering plants offered at many retail garden centers in Louisiana during late summer and early fall is cassia. These plants have now been re-classified as sennas, but most home gardeners still call them cassias.
Cassias are prolific fall bloomers. South Louisiana to north Louisiana, flowering time can vary by two to three weeks between September and November. They produce a massive bloom display that attracts plenty of attention.
Several different cassias are common in Louisiana, and many home gardeners may be confused as to which cassia they have.
Probably the best that fits a mostly tree-like description is Cassia splendida. Cassia splendida is usually the tallest-growing – making a 10-to-12-foot-tall tree in warmer locations of south Louisiana and a 4-to-6-foot grower in north Louisiana.
Other species are Cassia corymbosa and Cassia alata, which we may know as candlestick tree. You also may see popcorn cassia (Cassia didymobotrya) being sold and grown in Louisiana now. Candlestick trees and popcorn cassia have more herbaceous-type growth, and the other species have more woody-type growth.
Cassia corymbosa is most often a medium-to-large shrub.
The candlestick tree can vary greatly in size depending on age and location in Louisiana. It is common to see them 12-15 feet tall in the more southern portions of the state with a 6-to-8-foot height range common in the Florida parishes.
All cassia species have golden yellow flowers. The candlestick tree makes a candle-shaped bloom. The splendida species has showier blooms than the corymbosa species. It also produces fewer seed pods and stays in flower slightly longer than the corymbosa species.
All species have a tendency to need trimming and pruning occasionally to keep the plants in a manageable growth pattern. Right after new growth commences in spring is a great time to remove dead wood. You can also prune slightly during the growing season to manage growth. But don’t get carried away with pruning after early summer, or you’ll sacrifice fall flowers.
Cassias are trouble-free and easy to grow. Plant them in full to partial sun and fertilize regularly. Cassias need minimum irrigation. And once they’re established, irrigation is seldom required.
Cold weather the past two winters has been hard on cassias. While some are perennial, they have been slow to come back from the record cold, and many have needed to be replanted. Fall-planted cassia will not over-winter nearly as well as plants added to the landscape in the spring.
Cassias adapt well to containers, so consider this option in areas of the state that have not had success with them as perennials.
Cassias make a great background to herbaceous flower borders and mixed flower plantings. They are highly desired by butterflies, and bees go to the plants. Seeds of all species germinate readily, but people have the most success with seed from candlestick trees and the popcorn cassia. Plants also can be propagated by stem cuttings.
You can see more about work being done in landscape horticulture by visiting the LSU AgCenter Hammond Research Station website. Also, like us on Facebook. You can find an abundance of landscape information for both home gardeners and industry professionals at both sites.