Erythrina herbacea, native throughout the South, can be found growing on sandy, well-drained soil as a single specimen or in small clumps.
Erythrina herbacea is best known in Louisiana as mamou, but it also answers to coral bean, Cherokee bean and cardinal spear. A member of the Fabaceae (bean) family, mamou has compound (trifoliate) leaves, thorny stems and showy red flowers on tall spikes in late spring to early summer, followed by long slender pods opening to reveal bright crimson-red seeds.
Mamou performs well in full to partial sun on a site with well-drained, sandy-loam soil. At the edge of the woods would be ideal for this native herbaceous perennial. In the southern extent of its range (Zones 7-10), it may not die to the ground in winter, but rather grow into a tall shrub or small tree (to 15 feet) with a woody stem. In most other areas, it only reaches a height of about 3 to 4 feet.
Flowers are quite attractive to butterflies and hummingbirds (and people), and the colorful seed pods cling to the stem for several weeks in fall to early winter. Plants can be divided from larger clumps and it can be grown from seeds harvested and planted in fall after a little scarification (scratching the seed coat to allow for water penetration). Plants will not appear until the following spring, however.
Mamou is ideal for native or naturalistic landscapes, but it can also be used in a more traditional setting. I would recommend incorporating it into a mixed border planting, where other species will fill in when this one may not be at its peak.
Common Name: Mamou, coral bean, Cherokee bean or cardinal spear
Botanical Name: Erythrina herbacea
Color: Bright crimson-red flowers on upright spikes, followed by brown pods, splitting open to reveal showy red seeds
Type: Herbaceous to woody perennial shrub
Size: Normally reaches a height of 3-4 feet with a spread of 5-6 feet, but can achieve a height of up to 15 feet in the southernmost extent of its range (where it doesn’t die back to the ground in winter).
Exposure: Full sun to partial shade; seems to perform well and appears at home near the forest edge.
When to Plant: Late fall planting is ideal, both for seeds and clump divisions.
How to Plant: Seeds are harvested in late fall, scarified (sanded or filed to allow for water intake) and planted in prepared soil or containers outdoors. Alternatively, clumps can be divided in the fall, planting new offspring into loose soil that has been cleared of potentially competing weeds. New growth won’t appear until the following spring.
Soil: A well-drained, loose, organic or sandy-loam acid soil is ideal,but this plant is really quite adaptable to even relatively poor soils.
Watering: Irrigation is usually needed during the first year after planting,but also during periods of extended drought.
When to Fertilize: A balanced slow-release fertilizer should be applied upon planting and in early spring just prior to the emergence of new growth in the first couple years.
Buying Tips: The species may not be readily available in the garden center, but can be propagated from plants growing in a friend’s yard.
The common name “coral bean” comes from the showy, bright scarlet-red seeds clinging to the dark brown, twisted pods. Seeds have been used as beads for jewelry or other novelties, but they are also very poisonous, often used in Mexico as rat and fish poison.
(Photos by Peter Gallagher)