The African Tulip Tree (Spathodea campanulata) is an ornamental tree known for its large, vibrant flowers. Also called Fountain Tree, Flame of the Forest, Nandi Flame, and Squirt Tree, it is widely planted in tropical and subtropical landscapes for its aesthetic appeal.
Characteristics and Identification
The African Tulip Tree grows as an evergreen or semi-evergreen, reaching heights of 12 to 35 meters. It develops a rounded, spreading canopy and has a thick trunk with rough, gray bark. Its distinctive pinnately compound leaves, arranged in pairs along a central stem, can be up to 45 cm long. Each leaf consists of 3 to 19 oval or elliptic leaflets, 10 to 15 cm long, which emerge golden bronze and mature into dark, glossy green.
Its showy flowers are the most prominent feature. These large, bell-shaped or tulip-like blooms are orange-red or scarlet, though yellow varieties also exist. Flowers are arranged in dense clusters at branch tips, measuring 10 to 15 cm long and 7 to 7.5 cm wide. The velvety brown, ampule-shaped flower buds hold water, leading to the common name “Squirt Tree.” After flowering, the tree produces elongated, woody, boat-shaped seed capsules, 15 to 25 cm long, which split open to release numerous papery, winged seeds.
Native Range and Global Distribution
The African Tulip Tree is indigenous to the tropical dry forests and savannas of Africa, with its native range extending across West Africa, from Ghana and Angola, and inland to southern Sudan and Uganda. It is found naturally in secondary forests and can colonize grasslands within its native habitat.
Its aesthetic appeal led to its widespread introduction as an ornamental plant across tropical and subtropical regions. Its adaptability to various soil types and tolerance to dry seasons contributed to its successful establishment in new environments. Introduced to Hawaii in 1871, it was widely planted for reforestation in the early 1900s. The tree has since spread throughout the Caribbean, Southeast Asia, Pacific Islands, and parts of South America, becoming a common sight in urban landscapes and gardens.
Ecological Impact and Invasive Nature
The African Tulip Tree is an invasive species in many non-native tropical environments. It has a rapid growth rate and is a prolific producer of wind-dispersed seeds, with each pod containing 500 seeds. This enables it to spread quickly and colonize disturbed areas, agricultural lands, and natural ecosystems.
The tree outcompetes native vegetation, forming dense thickets and monocultures that shade out other plants and reduce local biodiversity. This aggressive colonization alters natural habitats and can displace native hardwood species. The African Tulip Tree also has allelopathic properties, releasing chemical compounds that inhibit the growth of other plant species. Regions like Hawaii, Fiji, Queensland (Australia), and various Pacific and Caribbean islands have experienced ecological challenges from this tree.
Toxicity and Potential Hazards
Various parts of the African Tulip Tree contain toxic compounds, affecting humans, animals, and some pollinators. The plant’s sap and other tissues contain saponins. Ingestion can lead to gastrointestinal upset in humans, and sap contact may cause skin irritation.
The tree’s toxicity extends to animals, including livestock and pets, causing illness if consumed. The nectar is toxic to native stingless bees in regions like Australia. This impacts local insect populations and disrupts pollination processes for other plants. Historically, a poison extracted from the hard central portion of the fruit was used to kill animals.
Management and Control Strategies
Managing the African Tulip Tree requires a combination of strategies due to its prolific seeding and vigorous regrowth. Mechanical removal includes hand-pulling or digging out young seedlings, effective only if the entire root system is removed to prevent suckers from regrowing. For larger trees, felling and ring-barking are employed, but these methods must be followed by further treatment to prevent coppicing and regrowth from stumps.
Chemical control is the most effective method for established trees. Herbicides like glyphosate, triclopyr, and picloram are used. These can be applied to freshly cut stumps, through stem injections, or as basal bark applications to the lower trunk. For stump treatment, herbicides are painted onto the cut surface, sometimes with additional drilling of holes to enhance absorption.
Biological control is being investigated and deployed in some areas. For instance, a gall-forming mite (Colomerus spathodeae) and a leaf-mining flea-beetle (Paradibolia coerulea) have been released in Pacific Islands like Rarotonga and Tonga to manage the weed. These agents undergo extensive testing to ensure host-specificity before release. Integrated management approaches, combining mechanical and chemical methods, are more cost-effective for long-term control. It is advised against planting African Tulip Trees where they are invasive; native alternatives should be considered for landscaping.