Erythrina, Coral Tree: Planting and Care

Description and botany

The Erythrina is a small tree from the Fabaceae family, like peas, wisteria, beans, or even Albizias. It originates from South America, particularly Bolivia, Brazil, and Uruguay. Found in tropical and subtropical regions, this explains why the Erythrina thrives in warm conditions and is only moderately hardy. It grows naturally on the edges of humid forests, along watercourses, marshes, and swamps.

Illustration of an Erythrina caffra

The Erythrina genus includes nearly 108 species of deciduous or semi-evergreen trees and bushes. In our gardens, the genus is mainly represented by Erythrina crista-galli, the cockspur coral tree, which is the hardiest species. It has given rise to several interesting cultivars and hybrids, such as Erythrina x Bidwillii. It is considered shrubby in our warmest regions, where it forms a small tree, and as a herbaceous perennial not exceeding 2m in height in more continental gardens.

You may also encounter Erythrina lysistemon or Erythrina caffra along the French Riviera, another beautiful but less hardy species.

In its native lands, the Erythrina grows into a tree 4 to 9m tall, but in our gardens, it reaches 2 to 4m in height with a spread of 1 to 2m in cultivation. The ‘Compacta’ form does not exceed 1.50m in any direction after 10 years. The plant develops from a strong taproot capable of fixing atmospheric nitrogen, an adaptation to poor soils. The Erythrina has a somewhat gnarled habit, with a slightly prehistoric appearance. It usually forms a single thick trunk with fissured bark in a crosshatch pattern, sometimes bearing a few curved black thorns.

Erythrina biwilldii, Erythrina caffra, and Erythrina crista-galli

The crown is broad, spreading, slightly umbrella-shaped, and sometimes weeping. The thorny branches bear ample foliage. The Erythrina is a deciduous tree that loses its leaves during the dry season and in autumn, producing new ones in spring. The alternate leaves, 10 to 15cm long, are divided into three large heart-shaped leaflets, leathery and with a thorny petiole. They are glossy blue-green to apple-green, sometimes variegated depending on the variety.

The Erythrina is prized for its strikingly original flowering, with large scarlet clusters earning it the nicknames “Cockspur Coral Tree” or “Coral Tree”. Flowering occurs earlier or later depending on the climate, starting in June in mild regions and around mid-August elsewhere. The flowers appear at the tips and along the current year’s shoots, grouped in clusters often exceeding 70cm in length, sometimes reaching 1m. They are quite atypical for pea-like flowers. Measuring 5 to 7cm long, they consist of five unequal fused sepals, with the largest upper one forming a downward-facing banner. The other reduced petals form a boat-like keel, revealing a curved, protruding tube containing the floral organs: a cluster of stamens and the pistil. With its folded banners, Erythrina x bidwillii stands out for its very elongated, almost tubular flowers. Most display a bright orange-red hue, hence its name “Cockspur Coral Tree” (Crista-galli meaning “cock’s comb” in Latin).

Melliferous and nectariferous, these vermilion flowers attract many pollinating insects, such as bees and butterflies. They give way to long brownish pods resembling beans, containing black seeds.

In traditional medicine, certain Erythrina species like Erythrina caffra have therapeutic properties and are used to treat arthritis, rheumatism, and toothaches.

Main species and varieties

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Planting the coral tree

Where to Plant It?

The Erythrina is a rather tender plant, hardy down to around -10/-15°C at the stump with protection, but the aerial parts can suffer at the slightest frost. It will thrive in gardens in the south of France. To achieve beautiful flowering, a very sunny and warm exposure is essential. In regions where frosts are brief and mild, position it against a south-facing wall, sheltered from cold winds, and protect the stump with a thick mulch in winter. This is why this bush is best suited to open ground in regions with mild winters, such as Mediterranean or mild Atlantic climates. Gardeners in more continental areas should grow it in containers as an orangery plant, to be stored away during the cold season.

In open ground, it thrives in full sun, sheltered from prevailing winds to preserve its vibrant flowering. Native to the marshy banks of South America, while it can grow in relatively dry soil, the Erythrina prefers soils that remain moist during its flowering period. Undemanding, it tolerates poor soils and thrives in any good garden soil that is moderately fertile, very well-draining, and preferably sandy. Avoid planting it in clay soil, as it cannot tolerate waterlogging or overly compact soils, which cause root rot.

Whether in pots or open ground, this bush adds an intensely colourful and exotic touch to gardens and terraces. It can be planted at the centre or back of a flowerbed, or as a standalone feature.

A stunning Erythrina planted in the ground in Provence

When to Plant the Erythrina?

The best time to plant Erythrina is in April-May, once all risk of frost has passed.

How to Plant It?

In Open Ground

Ensure your soil is lightened with well-draining materials at planting time if it retains water.

• Dig a hole 3 to 5 times wider than the root ball (at least 60 cm in width and depth)
• Create a good drainage layer (pumice, clay pebbles, gravel) at the bottom of the hole
• Plant the bush at collar level in the centre of the hole, using a mix of 1/3 compost, 1/3 garden soil, and 1/3 coarse sand
• Firm the soil
• Mulch the base
• Water thoroughly after planting and regularly, especially during the first few summers

In Pots

Again, good drainage is essential. Choose a pot at least 50 cm in diameter.

• Add a thick layer of drainage (gravel or clay pebbles)
• Plant in a slightly sandy substrate made of 1/3 garden soil, 1/3 compost, and 1/3 sand (or simply a mix of geranium compost + 1/3 sand).
• Bring the pot indoors or under frost protection at the first sign of cold in cooler regions

Cultivation, pruning and care

During the first few years, it’s best to monitor watering in summer. This bush enjoys cool soil in summer. Throughout the warm season, water abundantly and regularly to keep the base cool but never waterlogged. Allow the soil to dry out between waterings.

While it likes its roots to stay cool in summer, the Erythrina appreciates a good protective blanket bog at its base during the cold season. Apply a generous mulch (about 30 cm deep) around the stump in autumn to protect it from frost, especially in the first few winters. With annual hard pruning and a thick layer of mulch, it will be better equipped to withstand the cold.

An application of organic fertiliser once or twice a year in spring and autumn is recommended.

Erythrina crista-galli

In pots

Water regularly throughout summer. During the growth period, to encourage flowering, apply a liquid fertiliser for flowering plants every two weeks. From October onwards, move the pot into a cold greenhouse or a bright, minimally heated conservatory where temperatures won’t drop below 3°C. Continue watering about once a month. Replace the growing medium after 4-5 years, ideally after flowering.

How to prune it?

In temperate climates, it is often grown more like a herbaceous plant in the ground rather than a bushy plant because, after hard pruning, it can regrow from the stump and quickly produce beautiful, floriferous stems in midsummer. Therefore, if you want to encourage its development and keep it floriferous, it will tolerate severe annual pruning.

1. Cut back stems to 10 cm above the ground, before or after frost—either in early spring or November, depending on the climate—then mulch the stump to protect it from frost and winter moisture.
2. Regularly remove faded flowers to prolong flowering.

Propagation

Erythrina can be propagated by sowing seeds or by propagation by cuttings. However, fruiting is more unpredictable and difficult in our colder regions, and you’ll need to be patient as in any case, your young plants from sowing will take 3-4 years to flower. We recommend propagation by cuttings, which is easier to succeed with.

Sowing

If you already have an Erythrina in your garden, harvest the seeds from the tree, found in the pods once they have turned brown and dry.

• Soak the seeds for 2 days
• Sow on the surface of a good seed compost and cover them with 2 cm
• Place the sowings in a warm, humid environment at a minimum of 25°C
• Keep the substrate moist until germination
• Transplant into the garden or into pots once the young plants are large enough

Propagation by Cuttings

Semi-hardwood cuttings, taken in late summer, are simple and reliable.

• In late summer, take cuttings just below an eye, from shoots turning into hard wood, 4-5 cm long
• Remove the leaves from the lower third
• Plant the cuttings in a light, well-draining mix of sand and compost
• Keep the substrate moist in a humid environment until rooting, which is quick
• Transplant into individual pots
• Place them in a warm, bright spot throughout winter
• Transplant your cuttings into pots the following spring

Pair

Notable for its incandescent red flowering that lasts all summer, the Erythrina Cockscomb brings a decidedly exotic touch to both the garden and a well-exposed terrace. It helps create highly colourful and original summer scenes.

In mild climates, within a shrub border, pair it with Leucadendron ‘Safari Sunset’ (with striking purple foliage), with Grevillea rosmarinifolia ‘Clearview David’ or a Lagerstroemia indica ‘Rubra’, which also boast magnificent scarlet-red flowering, or simply with Buddleias. In an exotic or Mediterranean-inspired garden, it can be combined with plants that thrive under similar growing conditions, such as the Shrubby Sage ‘Violette de Loire’, Gauras, Phormiums, or tall Sedums like Sedum ‘Black Knight’, prized for its very dark, almost black foliage and its pink-red flowering from September to November.

It will stand out beautifully emerging from a sea of perennials. To create a striking flower colour contrast, surround its base with shrubby perennials featuring blue summer flowering, such as Salvias or Teucrium fruticans. In autumn, it complements asters, which are just as vibrant.

Erythrina crista-galli, Leucadendron ‘Safari Sunset’, Buddleia, and Grevillea rosmarinifolia ‘Canberra Gem’