Spathodea campanulata aka African Tulip Tree

Spathodea campanulata is a fast-growing tree that typically reaches 10–25 m in height, occasionally up to 35 m, with a broad, rounded, and often dense crown that spreads widely. Growth is rapid even in unfavorable conditions. With age the stem becomes hollow and the branches brittle, so mature trees should not be planted close to buildings or pavements.

The African tulip tree is native to tropical Africa, ranging from Senegal and Ghana in the west across to Sudan and Ethiopia in the east, and south through Cameroon, Uganda, Kenya, Tanzania, Angola, and Zambia. It was first documented by European botanists in 1787 on Africa's Gold Coast. Today it is widely naturalized across tropical regions worldwide including the Caribbean, Pacific islands, South and Southeast Asia, and parts of Australia.

Spathodea campanulata is highly adaptable in terms of soil, tolerating a broad pH range of 4.5–8 (optimal 5–7.5) and growing in a variety of soil types provided drainage is adequate. It thrives in well-drained, moist soils and has moderate salt tolerance. Good drainage is essential — it does not perform well in waterlogged conditions.

The optimal growing temperature for Spathodea campanulata is 27–30°C, with a tolerance range of approximately 23–34°C. It is a strictly tropical tree suited to USDA hardiness zones 10–11 and cannot tolerate frost. In cooler climates it must be grown under glass or in a heated greenhouse if grown at all.

Spathodea campanulata blooms in large terminal racemes; individual flower clusters can last for extended periods as buds open progressively. In tropical climates with distinct wet and dry seasons, flowering may be concentrated around the dry-season transition. Because the tree is semi-deciduous, some leaf drop may occur in strongly seasonal climates. Pruning of dead or broken branches should be carried out as needed given the brittle nature of the wood.

The flowers of Spathodea campanulata are large and cup-shaped, typically brilliant orange-red (sometimes yellow), 8–15 cm long with approximately five petals and contrasting yellow margins and throats. They are borne in terminal corymb-like racemes on 6 cm pedicels. The unopened buds are uniquely ampule-shaped and hold water — a feature that has made them popular with children as improvised water pistols. Open flowers hold rain and dew, attracting bird and bat pollinators.

A seedless yellow-flowered cultivar exists that is considered a non-invasive alternative to the standard orange-red form. The standard orange-red is the most commonly planted variety across tropical regions worldwide.

Spathodea campanulata is suited only to outdoor cultivation in frost-free tropical and subtropical climates (USDA zones 10–11). It requires full sun and moist, well-drained soil with annual rainfall of 1,300–2,000 mm. Established trees have moderate drought tolerance. The tree should not be planted near structures due to its brittle branches and shallow root system.

Spathodea campanulata reproduces prolifically from its broadly winged, wind-dispersed seeds, producing approximately 500 seeds per pod. Propagation is also possible via root suckers and stem cuttings. The tree is a pioneer species that establishes quickly on disturbed ground and wastelands. Its ease of propagation contributes significantly to its invasive success across tropical islands and mainland regions.

The tree is susceptible to butt and heart rot, and its wood deteriorates rapidly when in contact with soil. In Uganda, trees are attacked by lepidopteran species, termites, and bark beetles; nine insect pest species have been documented in Puerto Rico. Brittle branches and a hollow aging stem can also create structural vulnerabilities that invite secondary pest and fungal problems.

Spathodea campanulata flowers are pollinated primarily by birds and bats, which are attracted to the nectar-rich blooms. In Neotropical gardens, hummingbirds including the black-throated mango, black jacobin, and gilded hummingbird have been recorded as visitors. Barbets and other hole-nesting birds also exploit the soft wood for nesting cavities. The flowers can be harmful to bees — the pollen or nectar has been documented as toxic to Australian native stingless bees.

Seeds of Spathodea campanulata are consumed across parts of Africa, and the unopened flower buds contain a sweet, watery liquid that is also edible. However, caution is warranted: the fruit and seed kernels are described as poisonous and the seeds are considered "possibly toxic." Consumption of unverified quantities or preparations is not recommended. No culinary use is widely established outside traditional African contexts.

Traditional medicine across Africa uses several parts of Spathodea campanulata. Bark preparations serve as laxatives and antiseptics, and are applied externally for swollen cheeks and infant skin rashes. Unopened flower buds are used as tonics. Seeds, flowers, and roots are employed more broadly, with extracts applied against malaria, HIV, diabetes, dysentery, skin diseases, fever, wounds, liver complaints, and as antidotes to poisons. Kew's Medicinal Plant Names Services notes the species "has not been found explicitly cited in the medicinal literature" in a formal pharmacopoeial sense, and no WHO or EMA monograph exists for it — the uses documented above are primarily ethnobotanical.

The wood, though too weak for structural construction, is used for carving, blacksmiths' bellows, fuel, and charcoal production; it has also been used for plywood in the Philippines. In agroforestry systems the tree is planted for soil improvement, erosion control, reforestation, live fencing, and to provide shade in coffee plantations. The characteristic ampule-shaped flower buds, which hold water, are used by children as water pistols.