St Thomas and some other Virgin Islands in the summer months would flicker with the spectacular glow of the Delonix regia, otherwise nicknamed the glorious flame tree. The tree is originally native to Madagascar, an island just off the coast of Africa. It has been successfully planted in tropical and semi-tropical areas worldwide.
The tall 40-foot tree has a broad-spreading flat-topped crown that, in nature, can spread up to 70-foot wide. Each year, the deciduous tree flowers for several months from spring through to summer with an ornamental display of vibrant scarlet flowers amidst mimosa-like leaves. The name is derived from two Greek words, ‘delos’, which means evident and ‘onyx’, referring to the claw-like petals.
Europeans first noticed the striking tree in the 1820s. A young botanist called Wenzel Bojer from Bohemia was on an expedition in Mauritius, which lies 700 miles east of Madagascar. He collected specimens from the Delonix regia. The seeds have since spread around the world, creating welcome whorls of colour.
The fast-growing deciduous tree has excellent tolerance to poor soils and hard pruning, making it an ideal species for a bonsai. The leaves are pinnately and fern-like; the seed pods can reach up to 60 cm long, which look out of scale if allowed to grow. The tree is virtually evergreen in tropical climates, whilst in cooler subtropical regions, it will be deciduous. The flame tree does not tolerate cold temperatures and must be kept between 10 and 20 degrees Celcius.
Care Guidelines For Flame Tree Bonsai
The spectacular Delonix regia loves to be kept warm and ideally live in a sunny, wind-protected place outside in the garden during the entire growing season. Although the flame tree prefers to live outside, it can also be grown on a sunny window sill. Ensure that you carefully monitor nighttime temperatures because the tree cannot tolerate drastic temperature drops at all.
Bonsai experts recommend that the tree must be kept inside or in a heated conservatory or greenhouse. From autumn until spring, you must keep the flame tree between 10 and 20 degrees Celcius. The cooler and darker the overwinter space, the longer the flame tree will have to rest in its dormancy period without leaves.
During the winter months, photosynthesis ceases in deciduous trees and slows to a trickle in evergreen species. Tropical and sub-tropical trees are usually more tender to the cold. It is vital to prepare your tree for wintering. Trees produce carbohydrates and sugars which stop them from freezing. Therefore, it is essential to ensure that your tree is fed well during the growing season to have all of the proper nutrients ready for the winter.
When the cold nights have definitely passed, you can bring your tree out onto a sunny windowsill or your sun-filled garden and allow the tree to stretch, enjoy the warmth on its branches and allow growth.
During the growing summer months, the flame tree will need lots of water. You will need to practise careful watering techniques. Check the loam daily. Only water the bonsai when the soil gets ‘almost’ dry. Take care not to overwater the tree; this could lead to root rot, and it could lose all of its leaves and die. Your flame tree can tolerate an occasional short drought period.
In the dormant winter months, the tree will lose its leaves and will therefore require much less water. The flame tree enjoys a pH value between 4.50 and 7.50, so avoid hard calcareous water, which naturally has a higher pH value.
Soil And Fertilizing
Your flame tree will need lots of nutrients during the growing phase to grow its beautiful leaves and vibrant flowers. Therefore, it will require the application of a liquid fertiliser each week and a solid organic fertiliser every four weeks. Ensure that you administer well-balanced fertilisers. Nitrogen (N), phosphorus (P) and potassium (K) should be in equal proportion to promote healthy growth and perfect blooms.
To keep your flame bonsai in its very best shape and health, you’ll need to hard prune just as the tree comes out of dormancy and before the growing season begins. The leafless tree will allow you to carefully shape its body and plan the new season’s growth. Trim back branches to encourage the required shape and carefully remove any excess, damaged or wilted stems to promote healthy growth. The flame bonsai needs to have a good prune each summer to develop the perfect ramification and the beautiful umbrella-shaped crown that you’d find in the finest specimens in nature.
Gently prune the flame bonsai throughout the growing season to maintain optimal health. Thin out the interior branches to increase light penetration and air circulation throughout the tree to encourage balanced ramification. Regularly prune back vigorously growing branches to maintain shape. The spring is the best time to wire the branches and shoots while still young and pliable. You can gently shape older woodier branches with guy ropes. Keep a watchful eye on the wires and make sure that you remove them before they have the chance to bite into the bark, which will cause scarring.
You must ensure your blades are sharp and cleaned thoroughly with rubbing alcohol or antiseptic. You don’t want to cause damage or infection with blunt or dirty blades.
You must repot your bonsai as part of your regular maintenance plan. Your bonsai will become pot-bound as the roots grow to the shape of the pot and use up all of the nutrients. The lack of space and healthy nutrients will cause the tree to stop growing. Unless you take action, the tree will slowly die. Repotting your bonsai will again supply the tree with the nutrients it needs to grow and thrive.
Repot the Delonix regia bonsai every year or bi-annually. Before you repot your tree, carefully remove the bonsai from its pot in the early spring and pay attention to the root system. Your bonsai needs to be repotted if the roots are circling around the root ball or the pot. If the roots are contained within the nutritious soil it doesn’t need repotting, return it to the pot and repeat the exercise next spring.
To repot, begin by gently pruning the root system back by about one-third of the overall mass. Remove dead and wilted roots and then the strong roots that encircle the pot. Trim deadened roots back to the root mass. Repot the flame bonsai in fresh soil. The tree appreciates slightly acidic soil; adding some kanuma, a soft, highly acidic volcanic soil, is ideal for the required moisture retention and water drainage. The porous pebbles have similar physical characteristics to pumice. Water well with tepid water to allow the tree to settle.
Propagating a Delonix regia bonsai is relatively easy. When the seeds are fully ripe, the seedpods will drop from the tree. Carefully break open the seedpod and remove the seeds, lightly scarify the seeds and soak them in a container for a day or two before planting. Scarifying the seeds speeds up the germination process and allows water to enter the hard outer shell. Just nick the outer shell with a sharp knife.
Remove the seeds from the water and plant about an inch deep in up to 6 inches of moist potting mix. Place the container in a warm but partially shaded outdoor location. Maintain a slightly damp loam, and germination should occur between seven days and three weeks.
The flame tree proliferates quickly, and the little seedlings are no different. You will have to transplant them relatively quickly into a shallow, well-draining planting container to accommodate the root growth. You should make up the loam in equal parts of course sand, organic compost and nutrient-rich potting soil. To increase water retention, add a pinch of sphagnum moss or peat to the mixture.
Your chosen pot should have drainage holes. Cover these with mesh and fill a third of the container with your potting mix. Place the flame bonsai in the centre of the pot and fill with the remaining soil mixture. Water the bonsai evenly with tepid water until the excess drains from the holes.
Potential Pests And Diseases
One of the most bothersome intruders to your tree is scale. They are sap-sucking insects that prey on most kinds of trees and plants. There are two kinds of scale; soft and armoured. Both use long, needle-like mouthparts to suck out sap from the host tree. You can try to scratch them off manually or use a pesticide that will help rid the tree of the pest.
The tree can also play host to shoot borers, insect larva that bores into plant stems. Caterpillars, particularly the flame tree loopers, also like to feed on the tender leaves. Be careful not to overwater your Delonix regia bonsai, or you could cause root rot. If you think that this is the case, you can try and improve the tree’s condition by removing damaged roots and repotting them in well-draining soil.