Royal poinciana (Delonix regia)

The Royal poinciana (Delonix regia) provides welcome shade and spectacular color in the warm climates of USDA zone 10 and above. Showy black seedpods measuring up to 26 inches (66 cm.) in length decorate the tree in winter. The attractive, semi-deciduous leaves are elegant and fern-like. Read on to learn more about flame trees.

I. Appearance and Characteristics

Delonix regia is a species of flowering plant in the bean family Fabaceae, subfamily Caesalpinioideae native to Madagascar. It is noted for its fern-like leaves and flamboyant display of orange-red flowers over summer. In many tropical parts of the world it is grown as an ornamental tree and in English it is given the name royal poinciana, flamboyant, phoenix flower, flame of the forest, phượng vĩ or flame tree (one of several species given this name).

This species was previously placed in the genus Poinciana, named for Phillippe de Longvilliers de Poincy, the 17th-century governor of Saint Christopher (Saint Kitts). It is a non-nodulating legume.

Delonix regia is a medium-sized deciduous tree that grows to about 10 m (33 ft). The bark is light brown. Often creased at branches, it has prominent lenticels. The flowers are large, with four spreading scarlet or orange-red petals up to 8 cm (3 in) long, and a fifth upright petal called the standard, which is slightly larger and spotted with yellow and white. They appear in corymbs along and at the ends of branches. The naturally occurring variety flavida (Bengali: Radhachura) has yellow flowers.

The pods are green and flaccid when young, then turn dark-brown and woody as they mature. They can be up to 60 cm (24 in) long and 5 cm (2 in) wide. The seeds are small, weighing around 0.4 grams (6.2 grains) on average. The compound (doubly pinnate) leaves have a feathery appearance and are a characteristic light, bright green. Each leaf is 30–50 cm (12–20 in) long with 20 to 40 pairs of primary leaflets or pinnae, each divided into 10–20 pairs of secondary leaflets or pinnules. Pollen grains are elongated, approximately 52 μm in size.

In India, the trees are bare during the winter months from December to February. New leaves start to form in March-April. Flowers start to appear in April, reaching full bloom in May. Fruit pods are present for many months.

II. How to Grow and Care

Sunlight

These trees do best in full sunlight, so choose an area that gets at least six full hours a day. Without adequate light, you might not see the showy red-orange flowers for which the flame tree is known.

Temperature

This plant is native to the tropics. It is affected by temperature changes. It is evergreen in hot, dry conditions but deciduous in cooler temperatures. It grows best at temperatures ranging from 50° F (10° C) to 68° F (20° C). As a result, it is advised to place it in a sunny indoor or greenhouse environment. In the fall and winter, you should take insulation measures to keep it above 50 degrees Fahrenheit / 10 degrees Celsius. When your room is too cold, grow tents, and LED grow lights are a good solution. Installing a thermometer near the tree allows you to easily check the temperature and thus avoid low temperatures.

Watering

It is a general rule for Delonix to keep the soil moist at all times. When the weather is warm and sunny, it grows quickly. Young trees require a lot of water to grow, especially in their first summer, but don’t overwater as this can damage the tree’s roots. If it loses a lot of leaves when the temperature drops, it does not require frequent watering. Delonix regia can withstand light drought. Mature trees require very little additional irrigation.

Soil

A flame tree will grow in a variety of soil conditions as long as there is good drainage. The tree will tolerate clay, loamy, sandy, or gravelly soils in a wide pH range between 4.9 and 10.6.

Fertilizing

Delonix regia requires a lot of nutrients during the first two years of seedling growth to support growth and flowering. You can use organic fertiliser or a general-purpose liquid plant fertiliser. Apply an organic fertiliser every four weeks or a fertiliser with a balanced N-P-K ratio every week to promote healthy growth and flowering. However, take care not to overdo it.

Pruning

Delonix regia can withstand aggressive pruning. The pruning and shaping of bonsai can begin in the second year of growth. You should actually prune it more frequently. If you let it grow, it will soon become a jumbo. Follow bonsai pruning principles in the spring and summer to reduce excess internal branching, which increases sunlight exposure and reduces nutrient depletion. For shaping, use copper or aluminium bonsai wire. After flowering has finished in late summer, carefully remove damaged wood and excess shoots. Keep an eye on the bonsai wire, and don’t let it go too long because it can damage the epidermis of Delonix regia. Premium bonsai tools make it simple to prune and repot Delonix regia / Flame trees.

Propagation

Seed germination and cuttings are used to propagate this tree. To propagate the tree from cuttings:

• Using a sharp knife, take a cutting about one foot long. Remove any leaves from the lower third.
• Dip the stem in rooting hormone. Plant the cutting in a 1-gallon container filled with damp potting mix.
• Place in a warm outdoor location but away from direct sunlight. Keep the soil evenly moist until you see new growth, which can take several months. Once it starts growing, you can move it to a sunny location but let it grow into a strong sapling before planting it in the landscape.

Growing From Seeds

The seeds can be germinated and seedlings planted at any time but the seeds will need to be scarificed first to break open the seed coat and allow water to germinate the seed (see techniques below). If you already have a flame tree, harvest the long, strappy dark brown seed pods when they fall to the ground in the spring.

• Remove the seeds from the pod.
• Soften the coating of the seeds by soaking them in warm water for a day or two before planting in potting mix.
• Scarify the softened seeds by gently nicking or scratching each one with a knife; this process allows water in and speeds up the germination process. Some gardeners suggest rubbing the seed with sandpaper for a few seconds to generate peeling.
• Add well-draining potting mix to a 3- to 6-inch deep seed tray. Place each seed 1 inch deep and 3 inches apart. Pat the soil firm around each seed.
• Put the tray in a warm, partially shaded outdoor area. Keep the soil moist but not overwatered. Seeds begin to germinate in four to six days.
• Transplant 8-inch high seedlings to a 1-gallon container. Continue transplanting your seedlings as they grow until you are ready to select a site in your landscape to root the tree.

Growing in Pots

The flame tree is too big to be grown in containers but it can be grown and trained as a bonsai. As such, it will require potting every two years.

Overwintering

The flame tree can’t tolerate frost as it will rot the roots. If there is ever the danger of frost in the typically no-frost zones of 10 to 12 (USDA), cover smaller trees with burlap or a tarp overnight.

Repotting

If everything is in order, repot Delonix regia in early spring every year or two, depending on the size of the pot. Delonix regia’s root system will quickly take over the entire pot space due to its rapid growth. When its roots run out of room to grow, the entire bonsai tree will stop growing and eventually die. Remove Delonix regia from the pot with care, removing about one-third of the roots, and paying special attention to the dead roots and the strong roots at the bottom. Repot it in the pot, cover it with new soil, water it lightly to ensure the pot drains properly, and watch it grow.

Pests and Diseases

Common Pests and Plant Diseases

Although flame trees don’t have a lot of pests, some species of caterpillars may chew away on the leaves. However, it should not defoliate the entire tree. Additionally, spider mites can be an issue, particularly if the tree isn’t in a humid environment. If you spot spider mites, increase the humidity or set the plant outdoors. Scale insects can also be an issue. They’ll appear under the leaves, but can be removed with cotton swabs dipped in alcohol.

Phellinus noxious is a fungus that may cause the roots to rot. Choosing a spot with soil that drains well can help lessen the possibility that this fungus will invade.

Common Problems

Litter will happen if the branches (which are brittle) break or when the seed pods fall to the ground. You can help reduce the chances of the branches breaking if you can provide a spot with protection from winds and prune to form a strong branching structure.

The tree has a shallow root system, which not only competes with neighboring plants for space, but also makes the tree prone to being uprooted in strong winds.

III. Uses and Benefits

Ornamental uses

In addition to its ornamental value, it is a useful shade tree in tropical conditions, because it usually grows to a modest height (mostly 5 m or 15 ft, but it can reach a maximum height of 12 m or 40 ft) but spreads widely, and its dense foliage provides full shade. In areas with a marked dry season, it sheds its leaves during the drought, but in other areas it is virtually evergreen.

Medicinal uses

• The Delonix regia tree is endowed with numerous medicinal properties. It has antibacterial, anti-inflammatory, antifungal, antimicrobial, antioxidant, antimalarial, gastroprotective, and cardioprotective properties, as well as wound healing properties.
• The leaves of the Delonix regia tree are anti-diabetic. The methanol extract of these leaves is used to lower blood glucose levels.
• The leaves of the Delonix regia tree may have hepatoprotective properties.
• The plants’ leaves have antidiarrheal properties.
• It contains flavonoids, which help to protect the liver’s health.
• Antifungal properties of essential oil extracted from Delonix regia tree leaves
• The plant is used to treat a variety of physical conditions in ancient and folk medicine, including constipation, rheumatoid arthritis, inflammation, diabetes, malaria, and pneumonia.
• This plant is used to rehabilitate the soil.
• It can also aid in the fixation of atmospheric nitrogen.

Cultural significance

In the Indian state of Kerala, royal poinciana is called kaalvarippoo (കാൽവരിപ്പൂവ്, kālvarippūv) which means “the flower of Calvary”. There is a popular belief among Saint Thomas Christians of Kerala that when Jesus was crucified, there was a small royal poinciana tree nearby his Cross. It is believed that the blood of Jesus Christ was shed over the flowers of the tree and this is how the flowers of royal poinciana got a sharp red color. It is also known as Vaaga in many areas of Kerala.

Its blossom is the national flower of St. Kitts and Nevis, and in May 2018 the royal poinciana was adopted by the city of Key West as its official tree. Known locally as semarak api, Delonix regia is the city flower of Sepang, Selangor, Malaysia.

In Vietnam, this tree is called Phượng vỹ, or “phoenix’s tail”, and is a popular urban tree in much of Vietnam. Its flowering season is May–July, which coincides with the end of the school year in Vietnam. Because of this timing, the flower of poinciana is sometimes called the “pupil’s flower”. The tree is also commonly found on school grounds in Vietnam; however, after several incidents where a tree fell onto students, with one student killed, schools started cutting down or severely pruning the trees. Hải Phòng is nicknamed Thành phố hoa phượng đỏ (“City of red poinciana”).

The song “Poinciana” was inspired by the presence of this tree in Cuba.

In South India, these trees are common in schools, so children used to play with the stamens of the bud.