Tabebuia heterophylla
(pink trumpet tree)

Several Tabebuia species have been noted as invasive in parts of their native Caribbean range as well as where introduced to Pacific and Indian Ocean islands, mostly T. heterophylla, but also T. pallida and others. They are aggressive pioneer species, having rapid growth rates, forming a monoculture that casts a dark shade when established and few other species can survive under the canopy. They are valued for their timber and as attractive ornamental trees, and as such further introduction is likely, and it could easily become invasive in other humid, frost-free regions where it is not yet present, such as parts of Africa, Asia or Australia, or T. heterophylla may become invasive where it is already widely grown, such as in Florida, USA.

T. heterophylla is native to most Caribbean islands (USDA-ARS, 2008). Kairo et al. (2003), however, mistakenly note it as exotic and naturalized in the Caribbean, and record it as naturalized and invasive in the Dominican Republic (i.e. within its native range), both as T. heterophylla and a synonym, T. pentaphylla. However, T. pentaphylla is also a synonym of T. rosea, native to Central America and northern South America, and further clarification appears warranted, which may include the acceptance of a larger native range than stated here. T. pallida is regarded as having a more restricted native range than even T. heterophylla, limited to the Windward islands only, from Grenada to Guadeloupe (USDA-ARS, 2008). Caution should be used when using common names, as many of those which describe T. heterophylla also appear to be used on several other Tabebuia species, such as white cedar or roble.

T. heterophylla scored a very low score in a risk assessment for the Pacific (PIER, 2008), meaning that it was not considered as posing a significant risk, even though it is recorded as invasive on some Pacific islands. However, noting its aggressiveness and pioneering nature, it and T. pallida could easily become invasive if introduced to countries where it is not yet present, such as Australia and South Africa. It is available for sale as an ornamental species and has been considered as a timber species for plantations, thus, risks of intentional introduction are high. Any of the other closely related species such as T. rosea may also be considered as potentially invasive.

In its native Caribbean, T. heterophylla is particularly common in dry, coastal woodlands and in secondary forests, less commonly in dry or wet natural forests, and in some islands it can become widespread in abandoned pastures and secondary forests (Weaver, 1990). Some of the principle forest types in which it is found, for example, are dry evergreen forest in Puerto Rico and St Kitts-Nevis, dry scrub woodlands in the Lesser Antilles and British Virgin Islands, and it is also found (on one or two islands only) in bush land, fire grassland and standards, littoral woodland, secondary woodlands, seasonal forests, xerophytic rain forest and lower montane rain forest. In Puerto Rico, T. heterophylla regenerates and forms pure stands on grasslands and degraded soils, in particular on exposed upper slopes and ridges where competition from faster growing, larger, and more tolerant trees is lacking, and similarly, its persistence in the natural forest despite its slow growth, can be attributed to its ability to survive on poor sites where competition is minimized. It is tolerant of degraded sites and abandoned farm lands where it tends to form nearly pure stands (Weaver, 1990).

Considerable variation can be seen in plant morphology from different parts of the native range, which has surely added to the taxonomic confusion surrounding this and related species. T. heterophylla typically has five leaflets in Puerto Rico, but in dry areas and coastal thickets in the Lesser Antilles, trees are shorter, fruits and seeds smaller, and leaflet number declines to three, or at times to a single leaflet, and another variation found in Guadeloupe, Dominica, and Martinique has a single, broadly elliptic leaf (Little and Wadsworth, 1964).

Flowering may commence just a few years after planting, with large white to light purple perfect flowers are borne few to several in terminal and lateral clusters, or occasionally as individuals. Fresh seed germinate readily and at up to 100%, whereas after 3 weeks seed viability may fall to half, and no seed germination may be observed after 5-6 weeks (Weaver, 1990). However, under low temperature storage (at 5°C), seeds retained 100 germination capacity for up to 240 days (Huc and Bariteau, 1987). T. heterophylla can also be vegetatively propagated easily from shoot cuttings (Huc and Bariteau, 1987).

In Puerto Rico, flowering is mostly in the dry spring when all the leaves also fall, with fruits borne in May and June and fruit fall from July to September (Weaver, 1990), whereas in Guadeloupe, it was noted that flowering and fruiting had several peaks in wet zones but only a single peak in the dry zone (Huc and Bariteau, 1987). However, T. heterophylla is not a copiously-fruiting species in comparison with other trees from similar vegetation types. Seeds germinate in open areas and form dense stands of seedlings, T. heterophylla being an aggressive pioneer, especially in seedling and sapling stages. In open fields it regenerates well developing into a dense stand of seedlings, but after which it appears to stagnate, which may be due some combination of shallow, infertile soils, exposure and density of the seedling stands (Weaver, 1990). From data from plantations, tree growth was found to be 1 m in height and 1 cm in diameter per annum, though this could be reduced to one third in natural forests. Shaded seedlings grow very slowly or not at all, as in natural conditions seedlings are capable of surviving shade for years with no appreciable growth, and as such are classified as shade intolerant (Weaver, 1990).  

No pests are observed in natural forest situations, however, branches of roadside trees in Puerto Rico are often deformed into a witches' broom appearance, apparently by a virus possibly transmitted by the leaf hopper Protalebra tabebuiae, which also defoliates the tree or causes the leaves to turn yellow and fall prematurely (Little and Wadsworth, 1964). Few other diseases have been identified, and then only rarely, including a dieback disease Botryodiplodia spp.,a shoot borer Pachymorphus subductellus and the dry wood termite Cryptotermes brevis (Weaver, 1990).

Environmental

• Agroforestry
• Amenity
• Ornamental
• Revegetation

Fuels

• Fuelwood

Human food and beverage

• Honey/honey flora

Materials

• Wood/timber

Boats

Containers

• Boxes
• Crates

Furniture

Roundwood

• Posts

Sawn or hewn building timbers

• Carpentry/joinery (exterior/interior)
• Flooring
• For light construction

Veneers

Woodware

• Industrial and domestic woodware
• Sports equipment
• Tool handles
• Wood carvings

T. heterophylla is sometimes confused in the literature with the closely related T.pallida (Lindl.) Miers, as the latter has sometimes been used as a synonym, and with T. pentaphylla Hemsl. which is now treated as a synonym (but not T. pentaphylla auct.) (USDA-ARS, 2008). They appear to share similar environmental requirements and sympatric native ranges. Both have pink flowers thus are grouped together by some horticulturalists, who differentiate these from other yellow-flowering species, though T. pallida may also have white flowers. Foliar morphology is also similar, making differentiation more difficult. Ecologically, Tabebuia spp. share similar native ranges and habitats and pioneer qualities with a number of species of Cecropia and Tecoma (both also sometimes called ‘trumpet trees’), but T. heterophylla is generally differentiated morphologically by its opposite, palmately compound leaves, furrowed bark, and narrow, columnar crown.

Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.

No specific management information is available on control of T. heterophylla. As with all plants they can be dug up by hand or mechanically when small, and either cut, or cut plus a herbicidal stump treatment when larger, although its ability to coppice has not been ascertained. However, as a pioneer species in its native range, it may be assumed that, following initial invasion of disturbed sites that may lead to up to 100% cover with T. heterophylla, ecological succession will see a natural reduction over time, with a gradual increase in the numbers and frequency of native species.

29/02/08 Original text by:

Nick Pasiecznik, Consultant, France