Coral Bean (Erythrina herbacea)

Cardinal-spear, Cherokee-bean, Coral Bean, Red Cardinal

Coral bean (Erythrina herbacea) is a low shrub or small tree species with red tubular flowers that appear on the tall stalks in the spring. Late in the summer the pods mature by turning black and splitting open to reveal scarlet-colored seeds. Coral bean seeds are extremely poisonous. Grow the coral bean with other colorful plants, as the shiny leaves may become sparse during summer heat. Flowers are shaped like an arrowhead and blooms appear profusely on numerus annual stems. They are a magnet for hummingbirds.

I. Appearance and Characteristics 

Erythrina herbacea, commonly known as the coral bean, Cherokee bean, Mamou plant in South Louisiana, red cardinal or cardinal spear, is a flowering shrub or small tree found throughout the southeastern United States and northeastern Mexico; it has also been reported from parts of Central America and, as an introduced species, from Pakistan. Various other systematic names have been used for this plant in the past, including Erythrina arborea, Erythrina hederifolia, Erythrina humilis, Erythrina rubicunda, Corallodendron herbaceum and Xyphanthus hederifolius.

Coral bean grows as a low shrub or small tree, reaching around 5 m (16 ft) in height in areas that do not kill it back by freezing; elsewhere it may only reach 1.2 m (3.9 ft). Stems are covered in curved spines. The leaves are yellowish-green, 15–20 cm (5.9–7.9 in) long and 6 cm (2.4 in) wide. The leaves are divided into three 2.5–8 cm (0.98–3.15 in) arrowhead-shaped leaflets. The bark is smooth and light gray. The tubular flowers are bright red and grow in long spikes, each flower being 4–6.5 cm (1.6–2.6 in) long; the tree blooms from April to July. They are followed by 5–10 cm (2.0–3.9 in) pods containing bright red seeds, from which the tree gets its name. The plant forms a woody caudex. Toxic alkaloids, including erysopine, erysothiopine, erysothiovine, erysovine, erythrinine, erythroresin, coralin, erythric acid, and hypaphorine, are found throughout the plant. The leaves were found to contain erysotrine and erythrartine. These cause paralysis upon ingestion, much like curare.

Coral bean grows best in sandy soils and has moderate salt tolerance. It is found in open woods, forest clearings, hammocks, and disturbed areas.

II. How to Grow and Care

Sunlight

Coral bean shrubs bloom best in full sun for four to six hours daily, but they can tolerate partial sun, as they naturally occur along the edge of woodlands and forests.

Temperature and Humidity

The coral bean requires warm temperatures and thrives in USDA zones 8-11. In regions that experience cold winters with freezing temperatures, the coral bean can be grown as an annual rather than a perennial.

Watering

Water the coral bean once a week for the first growing season to encourage growth. The shrub does not tolerate excess wetness and should never be waterlogged. Once established, the coral bean is a drought-tolerant shrub and requires only supplemental watering during abnormally long dry periods. Be mindful of inadequate rainfall.

Soil

Coral bean is adaptable to a wide range of soil types but thrives in sandy, acidic soil. If you’re planting coral beans in a clay-rich area, supplement the soil with organic matter.

Fertilizing

The coral bean shrub does not require regular fertilizing. However, young plants benefit from fertilization in the spring to help boost growth. Use a balanced fertilizer, such as a 10-10-10, slow-release product. For the amount to use, follow product label instructions. This shrub also benefits from annual mulching to help retain moisture and protect the sensitive root system from cold temperatures.

Pruning

The coral bean does not require heavy pruning but benefits from light yearly maintenance. Do not prune during the first growing season. In the spring of the second growing season, you may prune any dead or cold-damaged growth and trim to shape where necessary. Though it can grow up to 10 feet tall, it has been known to shoot up to 25 feet high in warm climates where it does not die back each year.

Propagation

You can propagate the coral bean shrub via semi-hardwood cuttings and division. You can take semi-hardwood cuttings in the late summer or early fall once the stems mature. The shrub can technically be propagated by division of the root ball at any time, but it is best to do so once the coral bean is well established with excess growth that you can easily separate. Here’s how to propagate coral bean:

  • Cut a 4-6 inch section of a hardened, brown area of the stem.
  • Clip any seed pods or flowers from the cutting and an inch of bark from the bottom.
  • Dip the cutting into a rooting hormone.
  • Create a mixture of peat moss and coarse sand and insert the cutting into the pot.
  • Water and cover with plastic to retain moisture.
  • Place the pot in a shaded area.
  • The cuttings have rooted once you can gently tug on the cutting and it feels like it’s “in place” in the pot. Or, you may see some emerging growth on the cutting, which also means it has rooted.
  • Begin to harden off the potted seedlings by bringing them outdoors for a few hours a day in the spring. Keep under shrubs or out of direct sunlight. Bring them in at night. Do this for a week or two before you plan to plant the young plants in the ground.
  • Plant young plants 3 to 5 feet apart in the ground in the late spring or early summer.

How to Grow from Seeds

Coral bean seeds can be purchased from a nursery or garden center or collected directly from the plant. Take these steps:

  • Collect the pods that are filled with coral-colored seeds from the plant in the late summer or early fall.
  • Always wear protective gloves when handling coral bean seeds.5
  • Coral bean seeds benefit from scarification, or slightly scratching the seeds with an abrasive material, such as sandpaper, to increase the germination rate.
  • Soak scarified seeds in a jar of water until tiny roots emerge from each seed.6
  • Place germinated seeds in small pots with potting soil, keep indoors in indirect light, and slightly on the dry side (though not parched).
  • Plant germinated seeds in the ground after the threat of frost and once the temperatures are consistently warm, around late spring to early summer.
  • When planting several shrubs together, ensure you sow the seeds between 3 to 5 feet apart.

Potting and Repotting 

Coral bean may be grown in a container. It is best placed in full sun with southern exposure. Be sure to protect it from freezing during cold weather. Ensure that the potting medium is well-draining as the coral bean’s roots cannot tolerate sitting in water.

Overwintering

Coral bean is evergreen in tropical climates but will die back in freezing winter temperatures. However, it will regrow in the spring. You may overwinter coral bean indoors, preferably in a greenhouse.

Pests and Diseases

Common Pests & Plant Diseases

Coral bean is susceptible to infestation by a variety of moths. Leucoptera erythrinella are particularly harmful to the coral bean. The shrub is relatively unaffected by disease but can develop funguses and root rot.

Common Problems 

The problems you may have with coral beans are common to most shrubs. While the plant is relatively simple to care for, pay attention to issues like yellowing, browning, and wilting. Occasionally dust your coral bean to ensure proper photosynthesis and discourage discoloration.

Yellowing

Yellowing is the most common issue related to coral bean growth. Usually, this is caused by overwatering or inadequate nutrients like potassium, nitrogen, magnesium, and iron. Sunburn can also cause yellowing, in which case, move your plant to a slightly shadier area.

Browning

Browning on a coral bean can usually be attributed to dehydration or overexposure to direct sunlight. Consider adjusting your watering routine and placing your plant in a different location.

Wilting

Wilting is typically caused by dehydration. If your coral bean is particularly large, it will require more water than a smaller plant.

III. Uses and Benefits 

  • Ornamental uses

Coral bean is a popular plant in subtropical and tropical gardens, where it provides color from spring through fall. Showy flowers attract bees, hummingbirds, and other pollinators in the spring and summer, while bright-colored seed pods provide garden interest in the fall. Its tolerance to salt also makes it a good choice in coastal gardens.

  • Medicinal uses

Native American people had many medicinal uses for this plant, varying between nations and localities. Creek women used an infusion of the root for bowel pain; the Choctaw used a decoction of the leaves as a general tonic; the Seminole used an extract of the roots for digestive problems, and extracts of the seeds, or of the inner bark, as an external rub for rheumatic disorders.

  • Culinary uses

In some Central American countries the flowers are used in traditional cuisine. Mostly added to bean soup or meat patties, it is known for its mild narcotic properties.

  • Other uses

In Mexico, the seeds are used as a rat poison, while a fish poison is made from the bark and leaves.

Coral Bean (Erythrina herbacea) Details

Common name Cardinal-spear, Cherokee-bean, Coral Bean, Red Cardinal
Botanical name Erythrina herbacea
Plant type Poisonous
Hardiness zone 6a, 6b, 7a, 7b, 8a, 8b, 9a, 9b
Growth rate Slow
Harvest time Summer
Height 6 ft. 0 in. - 12 ft. 0 in.
Width 6 ft. 0 in. - 12 ft. 0 in.
Sunlight Full sun (6 or more hours of direct sunlight a day)
Soil condition Clay
Flower color Red/Burgundy