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 Erythrina thrives in warm conditions and is only moderately hardy. It grows naturally on the margins of humid forests, along watercourses, marshes and swamps.

Illustration of Erytrhina 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 like 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 on the French Riviera, another beautiful but less hardy species.

While in its native lands the Erythrina forms a tree 4 to 9m tall, in our gardens it will reach 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 at 10 years old. The plant develops from a powerful taproot capable of fixing atmospheric nitrogen, an adaptation to poor soils. The Erythrina has a somewhat nodose habit, a slightly prehistoric appearance. It generally forms a single thick trunk, with bark cracked in a criss-cross pattern and sometimes covered with a few curved black thorns.

Erythrina biwilldii, Erytrhina caffra and Erythrina crista-galli

The crown is broad, spreading, slightly umbrella-shaped, sometimes pendulous. The thorny branches develop beautiful 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 3 large heart-shaped leaflets, leathery and with a thorny petiole. They are shiny blue-green to apple green, sometimes even variegated depending on the variety.

The Erythrina is prized for its flowering, as original as it is dazzling, in the form of large scarlet clusters which have earned the bush its nicknames “Cockspur Erythrina” or “Coral Tree”. Flowering occurs more or less early depending on the climate, starting in June in mild climates, and from mid-August elsewhere. The flowers appear at the tips and along the year’s shoots, grouped in clusters often exceeding 70cm in length, sometimes reaching 1m. They are quite atypical for pea flowers. 5 to 7cm long, they consist of 5 unequal fused sepals, the uppermost and largest forming a banner pointing downwards. The other atrophied petals form a kind of boat’s keel from which protrudes a curved, prominent tube containing the plant’s floral organs: a cluster of stamens and the pistil. With its banners folded in two, Erythrina x bidwillii stands out for its very elongated, almost tubular flowers. Most display a bright orange-red colour, hence its name “Cockspur Erythrina” (Crista-galli meaning “cock’s comb” in Latin).

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

In traditional pharmacopoeia, some Erythrina species like Erythrina caffra have therapeutic properties and are used to treat arthritis, rheumatism and toothache.

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 be perfect in gardens in the south of France. To achieve beautiful flowering, a very sunny and warm position is essential. In regions where frosts are brief and not too severe, plant it against a south-facing wall, in a spot 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 our regions with mild winters of Mediterranean or mild Atlantic type. Gardeners in more continental areas should grow it in a container 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 spectacular flowering. Native to the marshy banks of South America, while it can grow in relatively dry soil, the erythrina will prefer 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-drained, and rather sandy. Avoid planting it in clay soil, as it cannot tolerate waterlogging or overly compact soils which cause its roots to rot.

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

A stunning Erythrina planted in the ground in Provence

When to plant the erythrina?

Planting Erythrina is best done in April-May when all risk of frost has passed.

How to plant it?

In open ground

It is essential to lighten your soil with drainage materials when planting if it retains water.

• Dig a hole 3 to 5 times wider than the root ball (at least 60 cm wide and deep)
• 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 in a mix of 1/3 compost, 1/3 garden soil and 1/3 coarse sand
• Firm down
• Mulch around the base
• Water thoroughly after planting and then regularly, especially during the first few summers

In pots

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

• Spread a good layer of drainage (gravel or clay pebbles)
• Plant in a slightly sandy substrate made up of 1/3 garden soil, 1/3 compost and 1/3 sand (or simply in a mix of geranium compost + 1/3 sand).
• Bring the pot under cover at the first sign of frost in colder 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 cool in summer, the Erythrina appreciates a good protective blanket bog at its base during the cold season. Mulch generously (about 30 cm deep) around the stump in autumn to protect it from frost, especially during the first few winters. With annual hard pruning and a thick layer of mulch, it will be better able 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 growth, to encourage flowering, apply a liquid fertiliser for flowering plants every fortnight. From October onwards, bring the pot into a cold greenhouse or bright, minimally heated conservatory where temperatures won’t drop below 3°C. Continue watering about once a month. Replace the compost after 4-5 years, doing so after flowering.

How to prune it?

In our temperate climate, it’s more commonly grown as a herbaceous plant in open ground rather than as a bushy plant because, after hard pruning, it can regrow from the stump and quickly produce beautiful, very floriferous stems in midsummer. Therefore, if you wish to encourage its development and keep it floriferous, it will tolerate severe annual hard pruning.

1. Cut back stems to 10 cm from the soil, before or after frosts – either in early spring or November depending on the climate – then mulch the stump to protect it from frost and winter damp.
2. Regularly remove spent flowers to prolong flowering.

Propagation

Erythrina can be propagated by sowing seeds or 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 as it’s easier to succeed.

Sowing

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

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

Cuttings

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

• In late summer, take shoots that are turning into hard wood, 4-5 cm long, just below an eye
• 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 occurs, which is quick
• Transplant into individual pots
• Keep them in a warm, bright place throughout winter
• Transplant your cuttings into pots the following spring

Pairing

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

In mild climates, within a shrub border, pair it with Leucadendron ‘Safari Sunset’ (with its striking purple foliage), with Grevillea rosmarinifolia ‘Clearview David’ or with 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 makes a striking feature emerging from a sea of perennials. To create a contrast in flower colour, surround its base with shrubby perennials that bloom blue in summer, such as Salvias or Teucrium fruticans. In autumn, it pairs beautifully with asters, which are just as vibrant.

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