Cassia didymobotrya waves a big yellow welcome for sulphurs. (photo by B. Boothe)

Bring Sunshine Yellow to Your Garden with Florida Cassias

By JoJo Lindquist

One of the best gifts from a plant and butterfly loving friend was a tiny Cassia seedling. I knew it was a caterpillar foodplant for a variety of sulphurs and would be a wonderful addition to the caterpillar resources in my garden. The showiest butterflies during our winter months are the large and butter-yellow Cloudless Sulphurs and Orange-barred Sulphurs. The Orange-barred Sulphurs, in particular are so poetically beautiful that perhaps they should be called Orange Bards. These butterflies have been a source of much joy with their wild aerial antics ­ spiraling and soaring endlessly near the Cassia. The best way to attract these butterflies is to plant their caterpillar foodplants ­ species of Cassia, Senna, and Chamaecrista. These three genus names are used interchangeably depending upon the botanists bias, so don't let this be too confusing. These fast growing tropical shrubs and trees bloom during the fall, winter and spring months. The small Cassia seedling I had planted grew 6' the first summer and to 10' the following year. Luckily the butterflies didn't find it until there was enough caterpillar food to go around. The high visibility of the sulphurs and ease of attracting them makes planting a cassia a perfect first-time butterfly gardening experience for individuals, school children, and horticultural therapy.

Many sulphurs across the country use pea or legume family plants as their caterpillar foodplants. This article will cover the use of cassia species in Florida.

Orange-barred Sulphur eggs decorate the flower buds of a tree cassia. Oct. 4, 1995. Mary Krome Bird Sanctuary, Homestead, Florida (photo by Jeffrey Glassberg)

Many cassias are cold-tender tropicals (USDA zone 10b-11) from the Bahamas, Argentina, and southeast Asia. Horticulturists introduced them here primarily because of their showy bright yellow flowers that bloom mainly in the fall, winter and spring months. They have compound alternate light-green leaves that are usually evergreen. The flowers are in terminal spikes or clusters. In Sarasota, Florida, (zone 10a) we need to plant them in warm, sunny, southern locations to avoid die-back to the ground during our brief freezes. They tend to be relatively drought-tolerant plants once well-established. These usually live 5-10 years, a relatively brief time, but grow rapidly.

Propagation and Care
Cassias are great plants to share with friends as they are easily propagated by seed or cuttings. Typical of pea-family plants, many long flat pods containing the seeds are produced each year. Collect the pods after they turn brown and separate out the large seeds. These can be planted in a light potting soil or directly in the ground. I have been told soaking seeds overnight and then scarifying them speeds germination. Apply a rooting compound to soft cuttings and plant in a sandy peat. It can be difficult to locate shrub varieties for purchase as they quickly outgrow the pots and do not last well in a nursery environment. Many cassias will re-seed under the parent plant. These seedlings are easily transplanted, so share them with butterfly-enthusiast friends. Nurseries specializing in butterfly plants may have cassias. Plant sales at local botanical gardens and butterfly exhibits may also sell plants.

A female Orange-barred Sulphur, richly suffused with color, lays her eggs on a Bahamian Cassia (Cassia chapmanii). March 31, 1997. Fairchild Gardens, Miami, Florida (photo by Jeffrey Glassberg)

Cassias are fast growing plants. To help them keep a compact form, prune back 1/3rd of the plant at a time. I prefer this method so there is plenty of food for sulphur caterpillars to enjoy. When used as a landscape plant only, it is recommended to cut them back hard after flowering. Because they tend to be weakly rooted, plant them where it is not windy. You may also have to stake the shrub/tree. They grow in a wide range of soils including alkaline, but prefer very well-drained soil with occasional deep watering. This works well with a "water-wise" garden.

Select a Planting Location
Most cassias have a fairly wide spreading growth habit so leave some room (6' or more for the larger ones) when you plant them. They work well in the background of a large mixed border planting or in front of a dark green shrub-mass. Remember to plant them where they are protected from the winds. The butterflies will appreciate a calm warm sunny location, too. There are several small tree-sized cassias which can be used to make a shady alcove in your butterfly garden. I encourage you to spread caterpillar food sources throughout your yard to give the caterpillars a better chance of escaping predators.

A mated pair of Barred Yellows, a delightful but diminutive species whose caterpillars feed on cassias. Sept. 22, 1994. Cabbage Swamp, Pasco Co., Florida. (photo by Jeffrey Glassberg)

Native Cassias
Bahamian Cassia, Cassia chapmanii (C. bahamensis) is a slow growing, showy shrub indigenous to the coastal pinelands of South Florida and the Bahamas. It tolerates alkaline soils and salt. Partial shade is OK. This plant is strictly for tropical Florida.

Partridge Pea (Cassia fasciculata and other names) is a fine textured low-growing (1'-3' ht.) annual herb found from Texas to Florida north to New Jersey. It grows and reseeds in pinelands, open woods and disturbed sites, and has become naturalized on some coastal dune systems. Plant it away from walkway areas as it will stick to your clothing. Partridge Pea is a good addition to a meadow.

Favorite Local Caterpillar Foodplants
Two varieties are particular favorites of our home grown sulphurs. They are Cassia bicapsularis and Cassia didymobotrya. The C. bicapsularis is a 10'x10' shrub which is covered in the fall with yellow flowers. It needs pruning to keep it compact. The flowers are borne on the ends of the branches. Cassia didymobotrya is a larger, lankier shrub or accent tree. It has candle-shaped spikes that bloom all year, but more heavily in the winter months. The butterflies will choose these species over others grown in our area and they are both very easy to grow. Both can freeze to the ground in a prolonged 28 degrees chill.

Cloudless Sulphurs need energy for their long-distance flights. Here a female nectars at a morning glory. Sept. 29, 1996. Savannah, Georgia (photo by Jeffrey Glassberg)

   Some Butterflies that Use Cassias as Caterpillar Foodplants

White Angled-Sulphur. Strays from Cuba and Mexico to south Florida and south Texas.

Yellow Angled-Sulphur. A rare stray north from the West Indies and Mexico.

Cloudless Sulphur. Widesread and common over much of the South.

Orange-barred Sulphur. Florida and south Texas

Sleepy Orange. Southern 1/4 of the United States.

Mexican Yellow. Immigrant from Mexico to much of the central United States.

Little Yellow. Southeastern United States immigrating northward into most of the eastern United States and into southern Canada.

Barred Yellow. Southeastern United States.

Left: The fabulous pupa of a Cloudless Sulphur. Aug. 9, 1996. Patagonia, Arizona (photo by Jeffrey Glassberg)

Right: Sleepy Orange is yet another species whose caterpillars feed on cassias. Oct. 23, 1995. Roma, Starr Co., Texas (photo by Jeffrey Glassberg)

Left: Bahamian Cassia (Cassia chapmanii) is a pleasant garden plant that helps to populate the landscape with sulphurs. March 31, 1997. Fairchild Garden, Miami, Florida (photo by Jeffrey Glassberg)

Right: All the life stages of phoebis are pretty great. Here an Orange-barred Sulphur caterpillar noshes on some Cassia bicapsularis flowers. (photo by Pat Donnelly)