Cassias provide spectacular color in late summer and fall. Photo courtesy of LSU AgCenter
If your yard is low on late summer/fall bloomers, you might want to try cassia, which bears loads of golden flowers for a long period. They're perennial in South Louisiana and will come back after mild winters in the rest of the state. Here's what Dr. Allen Owings has to say about them:
By Allen Owings, LSU AgCenter horticulturist
One of the popular fall-flowering plants is cassia. Sometimes these plants are now called sennas.
Cassias are prolific fall bloomers and are one of the plants in landscape settings that are a “showstopper” in October and November. They produce a massive bloom display that attracts plenty of attention.
Several different cassias are common in Louisiana. Probably the best that fits a mostly tree-like description is Cassia splendida. Other species are Cassia alata (which we may know as candlestick tree) and Cassia corymbosa. Cassia splendida is usually the tallest growing – making a 10- to 12-foot-tall tree.Cassia corymbosa is most often a medium to large shrub. And 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 6-8 foot height range common in the Florida parishes. Candlestick trees have more herbaceous-type growth, and the other species have more woody-type growth.
Candlestick tree makes a candle-shaped bloom of golden yellow flowers. The other species also have golden yellow flowers. The splendida species has more showy blooms than the corymbosa species. It also produces fewer seed pods and stays in flower slightly longer than thecorymbosa species.
Are cassias annuals or perennials? They typically survive winters in south Louisiana very well. The candlestick cassia is the one that is most likely to not survive winter growing conditions.
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 will 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 once established.
Seeds of all species germinate readily, but people have the most success with seed from candlestick trees. Plants also can be propagated by stem cuttings. Cassias make a great background to herbaceous perennial borders and are highly desired by butterflies.