​Senna

senna

( SEN - uh )

At-A-Glance Information

This genus, commonly called Senna, includes both evergreen and deciduous shrubs and trees that need full sun to light shade and little to moderate water to perform well in the landscape. These trees will attract butterflies and other pollinators to the garden, and are grown for their winter and springtime shows of flowers. Pods follow blooms and can create a litter problem if not pruned off after flowering fades. Use Senna in drought-tolerant, naturalized, or arid gardens as backdrops, accents, or for erosion control in sloped areas. Take care when planting these shrubs and trees in the landscape, as some species have plant parts that are toxic to humans and pets of ingested.

senna Species and Varietals

The genus Senna is a member of the plant family Fabaceae and includes between 260 and 350 species. The plants in this species are closely related to those in Cassia (Golden Shower Tree). The best growing zones for Senna vary depending on the species. For more information, see the descriptions below. To find your zone, click here: Zone Map.

Senna acclinis (Rainforest Cassia, Brush Senna, Rainforest Cassia)
These rare shrubs are endemic to eastern Australia, and produces bright yellow-golden flowers in spring and summertime. These plants reach up to 10 feet tall, and are great pollinator plants. This species is suited for USDA hardiness zones 10 and 11.

Senna alata (Cassia alata) (Emperor's Candlesticks, Candle Bush, Candelabra Bush, Empress Candle Plant, Ringworm Shrub, Seven Golden Candlesticks)
This species is native to the areas between Mexico, the West Indies, and Paraguay, and is considered an invasive species in some areas of the world. These shrubs reach between 10 and 13 feet tall when mature and have leaves that close up in the dark. Flowers are yellow and bloom in upright infloresences. These plants are commonly called Ringworm Bushes due to their antifungal properties. This species is considered invasive in Asia, Oceania, the Pacific, and East Africa.

Senna alexandrina (Alexandrian Senna, Egyptian Senna, Tinnevelly Senna, East Indian Senna, Sene de la Palthe, Sanamki, سنامكي, Asharj, عشرج, Asharq, عشرق, Sana Makka, سنا مكة, Eshrag, عشرج, Eshrej, عشرق, Khartoum Senna, Nubian Senna)
This shrubby plant reaches between 20 and 40 inches tall when mature. Flowers are yellow and foliage is green. These shrubs are native to Egypt and Sudan, and is widely cultivated in India and Somalia. These plants are suited for USDA hardiness zones 9-11.

Senna armata (Spiny Senna, Desert Senna)
These rare shrubs are native to desert regions around the intersection of California, Nevada, Arizona, and Baja California. They prefer to grow in sandy or rocky habitats, and reach up to 3 feet tall. Flowers are yellow and bloom in spring and summer. Spiny Senna is suited for growing in USDA hardiness zones 8-10.

Senna artemisioides (Cassia aremisioides) (Feathery Cassia, Silver Cassia, Silver Senna, Wormwood Cassia, Puny Bush)
This species does best in USDA hardiness zones 8-11 or Sunset growing zones 8, 9, 12-16 and 18-23 and are native to Australia. These shrubs are evergreen, and have gray leaves and yellow flowers in late fall, winter and springtime, though blooms often hold on through the beginning of summer. These are heavy re-seeders, but are very drought tolerant (though will flower better with moderate to regular water). Certain subspecies are considered invasive in Qatar.

Senna atomaria (Flor de San Jose, Palo Zorillo, Ruscón, Palo de Burro, Bonchi Largu, Kachu di Biná, Vara)
This species is native to Mexico, Central America, the Caribbean, Colombia and Venezuela. These shrubs or small trees have a multitude of uses, and reach about 6.5 to 40 feet tall when mature. Flowers are yellow. This species is suited for USDA hardiness zones 8-11.

Senna auriculata (Matura Tea Tree, Avaram, Tanner's Cassia, Ranawara, රණවරා, Avaram Senna, Avarampoo, ஆவாரை, Tarwad, तरवड, Tangedu, తంగేడు)
This shrub is the state flower of Telangana, India, and is native to India and Sri Lanka. These shrubs have smooth, cinnamon colored bark and green foliage. Flowers are large and bright yellow. These trees are commonly used for landscaping along roadways and in gardens, and are tolerant of drought and dry conditions but not cold temperatures. Matura Tea Tree grows well in USDA hardiness zones 8-11.

Senna bicapsularis (Rambling Senna, Winter Cassia, Money Bush, Yellow Candlewood, Butterfly Bush)
This species is native to South America and the West Indies, and is a semi-evergreen shrub that reaches between 6.5 and 60 feet tall and has a low, spreading crown. The main cultivar of this species is 'Worley's Butter Cream' (also called 'Buttercream'), with pale butter-cream to yellow blooms instead of the species' golden yellow. These plants are considered invasive in some areas of the world, including East Africa, the Galápagos Islands, and New Caledonia.

Senna circinata (Coiled Cassia, Spring-Pod Cassia, Rounded Cassia)
This species is endemic to eastern Australia, and forms a shrub or small tree that reaches about 7 feet tall when mature. Flowers are yellow, and appear in wintertime in the plant's native range. Leaves are thin and almost needle-like. The specific epithet of this species refers to the flattened, spirally coiled pods that follow flowers. Coiled Cassia grows well in USDA hardiness zones 8-11.

Senna corymbosa (Cassia corymbosa) (Flowery Senna, Argentine Senna, Buttercup Bush, Tree Senna)
This species takes the form of an evergreen shrub, and does well in USDA hardiness zones 8-11 or Sunset growing zones 12, 13, 21-24, H1 and H2. It is native to South America and reaches 10 feet tall and a little wider at maturity. Leaves are dark green, and flowers bloom in round clusters in spring through fall. Self-seeds profusely. This species is considered invasive in South Africa and regions of the southern United States.

Senna didymobotrya (African Senna, Popcorn Senna, Candelabra Tree, Peanut Butter Cassia)
These plants are used worldwide as ornamentals, cover crops, and green manure. They grow well in USDA hardiness zones 9-11 and are native to Africa. The species forms a fragrant shrub that reaches about 16 feet tall when mature. The common names for these plants refer to the various smells they give off. This species is considered invasive in South Africa, East Africa, and regions of Australia.

Senna gaudichaudii (Kolomana, Blunt-Leaved Senna, Gaudichaud's Senna, Climbing Senna, Kalamona, Heuhiuhi, Uhiuhi)
Native to various Pacific Islands, southeast Asia, and Queensland, Australia, this species produces yellow flowers on a shrub or tree that typically reaches between 7 and 10 feet tall when mature. Foliage is green. These plants are suited for growing in USDA hardiness zones 10-12.

Senna marilandica (Cassia marilandica) (Maryland Senna, Maryland Wild Senna, Wild Senna, Southern Wild Senna, American Senna)
This flowering perennial plant is native to the United States, and blooms in summertime. Flowers are yellow, and foliage is green. These plants can reach about 6 feet tall and grow well in USDA hardiness zones 4-9.

Senna multiglandulosa (Cassia tomentosa) (Wooly Senna, Downy Senna, Glandular Senna)
This evergreen shrub grows well in USDA hardiness zones 8b-11 or Sunset growing zones 13, 17, and 22-24 and is native to tropical regions of the world. It reaches 12 to 15 feet tall and wide, producing upright clusters of yellow flowers at branch tips in winter and early springtime. Leaves are dark green on top, white and hairy beneath. This species needs regular water to perform well and is considered invasive in Australia and New Zealand.

Senna multijuga (November Shower, False Sicklepod, Cachimbo, Chipilín, Dormilón, Guajillo, Picho Guacamayo, Pau-Cigarra, Aleluia, Aleluia-Amarela, Canafístula, Árvore-da-Cigarra, Cigarreira, Marimari)
These trees are native to wet, tropical areas in a region that spans from Mexico down through Central America to tropical South America. They can reach 33 feet tall when mature, and are used in restoration projects, as ornamental plantings, and as street trees. This species is considered invasive in Hawai'i, Australia, and Puerto Rico.

Senna nemophila (Senna artemisiodes filifolia, Cassia eremophila) (Desert Cassia, Desert Senna, Green Feathery Cassia, Green Feathery Senna)
This evergreen shrub does well in USDA hardiness zones 8-11 or Sunset growing zones 12-24 and is an Australian native. Foliage is green, but otherwise this species is very similar in growth habit and flowering to Senna artemisioides. These shrubs can reach up to 4-8 feet tall and just as wide.

Senna occidentalis (Coffee Senna, Styptic Weed, Septicweed)
This offensive-smelling weedy shrub is native to the southern United States, Mexico, and South America. It typically grows to 4-7 feet tall when mature, and produces yellow flowers. Coffee Senna grows well in USDA zones 9-11 as a perennial, or as an annual in cooler regions. This species is considered invasive in tropical subtropical and warm temperate regions around the world, including in Australia, the southeastern United States, East and South Africa, the Pacific Islands, Oceania, and regions of Asia.

Senna oliogophylla (Cassia oligophylla) (Outback Cassia, Outback Senna, Bloodbush, Buttercups)
Native to Australia, this species reaches 5 feet tall and wide and has glossy grayish-green leaves and red stems. Springtime flowers are yellow, and followed by attractive reddish brown seed pods. Needs excellent drainage to perform well.

Senna pendula (Easter Cassia, Winter Senna, Climbing Cassia, Golden Shower, Pendant Senna, Valamuerto)
This species is used around the world as an ornamental plant, and is considered a weed in Australia. These plants are native to South America, and is a fast-growing, scrambling shrub with arching stems and branches. Easter Cassia typically reaches between 6.5 and 23 feet tall when mature. The species grows well in USDA hardiness zones 9-11. Easter Cassia is considered invasive in Australia, and Florida (United States).

Senna phyllodinea (Senna artemisioides petiolaris, Cassia phyllodinea) (Silver Leaf Cassia, Silvery Cassia, Silver Leaf Cassial, Woody Cassia)
This species of Senna does well in USDA hardiness zones 8b-11 or Sunset growing zones 12-24 and is native to Australia. It quickly reaches 4-6 feet tall and just as wide at maturity with silvery-grey leaves that are curved. Flowers are yellow and bloom from fall through spring.

Senna splendida (Cassia splendida) (Golden Wonder Senna, Showy Senna, Fall-Flowering Cassia)
This species takes the form of an evergreen shrub and grows well in USDA hardiness zones 9-11 or Sunset growing zones 12, 13, 21-24, H1 and H2. This species has an open habit and tops out around 9-12 feet tall and 6-10 feet wide. Leaves are bright green and yellow flowers bloom at branch tips in fall and winter. Heavy seed pod producer. Garden ornamental cultivars of this species include 'Golden' (to 18 ft. tall and 15 ft. wide with large gold flowers) and 'Ray's Splendor' (with smaller foliage and flowers, better for warmer climates).

Senna surattensis (Cassia surattensis) (Scrambled Eggs, Kolomana, Glossy Shower Tree)
Native to tropical areas of Asia, Polynesia, and Australia, this evergreen species grows best in USDA hardiness zones 9-11 or Sunset growing zones 19-24, H1 and H2. They typically reach up to 12 to 20 feet tall and 10 to 18 feet wide in garden or urban cultivation. Blooms are present almost year-round at the ends of branches in frost-free zones. This species is considered invasive in various regions of Asia, the Pacific Islands, and Hawai'i.

Senna wislizenii (Cassia wislizenii) (Shrubby Senna, Wislizenus' Senna, Canyon Senna, Dwarf Senna, Palo Prieto, Pinacate)
This species, best in USDA hardiness zones 7-10 or Sunset growing zones 10-13, is native to southern Arizona, Texas and Mexico. It has a rounded shape and reaches 5-8 feet tall and 5-10 feet wide. Branches are rigid and upright, clothed in bright green leaves and holding clusters of yellow flowers at the tip in early summer through fall.

Caring for senna

Senna trees and shrubs produce moderate to heavy seasonal litter consisting of dropped small leaflets, spent yellow flower petals, and persistent dry seed pods; consider planting away from gutters, roofs, and outdoor gathering areas. These trees should be planted in a spot in the landscape that receives full sun. Senna requires between 6-8 hours of direct sun daily to flower and grow well. These trees can grow in a variety of soils, including sandy, loamy, and slightly rocky. Soil must drain well and have a slightly acidic to neutral pH (between 6.0 and 8.0). If local soil is overly clayey, it will need to be amended with sand or organic matter in order to make it well-draining. After planting, mulch around the base of the tree, ensuring that mulch stays about 3 inches away from the trunk. Water newly installed trees regularly to help them establish a strong root system. Once mature, these trees are drought-tolerant., benefitting from deep waterings during elongated periods of drought. Avoid overwatering, and allow soil to dry out between waterings to discourage root rot issues.

Prune young trees in order to create a single-trunked tree. Yearly pruning for cleanup should be done after the main blooming period in summertime. These trees can be pruned to control their shape and size, so that they stay the right height for smaller gardens. Prune lightly and avoid removing more than a third of the foliage at any one time, as this can reduce flowering for the year. Prune after the main bloom cycle ends; pruning too late in the season can trigger new growth that is vulnerable to frost in cooler areas. They can take between 10 and 40 years to reach full height. Pods that follow flowers can be left on the tree for ornamental purposes, or trimmed off if desired (especially if you do not want more trees). The seeds can germinate well under the right climate conditions, so having a lot of volunteer seedlings is common around the base of mature trees. Senna trees can last for

Propagation

Senna can be propagated either by using cuttings or from seed. To ensure that your propagated plant will have the exact same qualities and characteristics as the parent plant, use the cutting method. If you would like to experiment and see what plant you can grow from seed, just keep in mind that it will not necessarily be the same as the parent plant. To propagate your Senna tree, follow the instructions below:

Propagating Senna by Cutting

Gather your materials. You'll need a clean, sanitized, sharp pair of garden shears, rooting hormone, a pencil, and a 3-inch pot filled with well-draining compost or other organic material. A good substrate for propagation of cuttings is a light blend of 1/3 pasteurized soil or compost, 1/3 sand, vermiculite or perlite, and 1/3 coconut coir or peat moss.
In spring or early summertime, choose the plant that you'd like to propagate. Ensure that this plant has had a good watering the night before, as this will improve the chances your cutting will take root. Cut one or more 6 inch portion(s) of the end of a non-blooming branch and strip the leaves off of the lower half. Make a hole in your planting medium by pushing your pencil into the soil. Dip the end of the stem in rooting hormone, and plant it in your pot. Fill in soil around the cutting to support it, but do not pack it down too much.
Moisten with water, and ensure that the pot has good drainage. Your pot should be kept in warm, sunny conditions indoors (and not in direct sunlight). Water whenever your soil is dry under the top layer. After about four to six weeks have passed, your cutting should be rooted. When you notice new growth, you'll know you have roots.
Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring, when you can transplant it to its new home. Ensure that the last frost of the year has occurred before doing this, as it can seriously damage your new shrub or tree.

Propagating Senna by Seed

Keep in mind that the plant you get from seed will not necessarily mimic all of the characteristics of the parent plant. To propagate by seed, you will need a paper bag, a pot or tray filled with well-draining compost or other organic material, a spray bottle and a fork. The best potting medium for seed germination is a light blend of 1/3 pasteurized soil or compost, 1/3 sand, vermiculite or perlite, and 1/3 coconut coir or peat moss.
Harvest your seeds. The seed pods on Senna plants are pretty easy to spot, they're long, dark and dangle from the branches, left behind after flowers have faded. Once they have dried out and begun to split open, you can harvest the seeds inside. Cut them off of the plant, placing them in a paper bag. Harvest as many as you can, and place the paper bag in a dry, cool, dark area. They will begin to split open and release the seeds contained inside. Once they have been released, take them out of the bag and put them in a container so you can work with them.
Senna seeds have a hard coating that protects them, but this coating also makes it a little difficult to get them to germinate. We can help the process along by scarifying them with sandpaper (or simply rubbing them against an abrasive surface). Do this with as many seeds as you can; they will probably not all sow, and the ones that do will be of varying characteristics. The more seeds you plant, the more chances you will have to get the resulting plant you want. Place your seeds in lukewarm water for 24 hours. Viable seeds will sink to the bottom, and non-viable seeds will float to the top. You can discard any seeds that float.
Water your prepared seed tray or pot filled with soil, and ensure that good drainage is occurring. Place your seeds in your prepared pot or seed tray about a quarter inch to a half-inch under the soil surface. Cover them with soil and water with your spray bottle. Place your tray of seeds in a warm area that receives bright, indirect light. A greenhouse is the most ideal climate, but a planting tray inside a window will do as well. Germination usually takes between 14 and 27 days from sowing. Once you begin to see seedlings sprout and they are able to be handled, transplant them to their own individual 3-inch pots, filled with the same potting medium as described in Step 1. Loosen the seedlings from the potting medium by digging down with the tines of your fork about an inch and a half, gently working the seedling up until it is out. Then, replant the seedling in its individual pot.
Keep the seedling's potting medium moist, but not wet, by spraying the soil with your spray bottle. Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring (after the danger of frost has passed), when you can transplant it to its new home.

Senna seed pods contain between 6 and 20 seeds each and turn dark brown and brittle when mature.

Senna seeds are flat, brown, and can appear square or rounded to oval.

Problems and Pests

Certain Senna species are considered invasive in some regions; see the species descriptions above for more information. Check with local authorities before planting. Senna plants are generally tough and resilient in the landscape, though they can be susceptible to developing issues with the following pests and diseases: