Hippomane mancinella L.
Euphorbiaceae MANZANILLO, MANCHINEEL
Occasional evergreen canopy tree (10-20 m) and an integral component of the vegetation that fringes the sandy coastline. Appreciated for the shade it provides along harsh and hot tropical beaches, this species is at the same time a dangerous one, due to the large quantities of caustic sap contained in its leaves, twigs, bark, and fruit.
Description: Manzanillo trees sport many growth forms that are determined largely by the life-history of the individual. Some boles are erect and mostly straight, reaching 20 m or more in height and 60 cm in diameter. Others start out inclined, growing diagonally over the beach, and are later toppled by the shifting, sandy soils that characterize their habitat. After falling, they may continue to thrive as erratically meandering trees with large portions of their trunks completely covered by beach sand. Such boles, still old and thick, may not exceed 5 meters in height. All Manzanillo trunks lack buttresses and are clad in gray, cracked bark. The tree’s stout limbs subdivide many times into a large number of thin twigs that bare foliage only at their tips. When a fresh leaf cover exists, the crown becomes moderately dense and thick – effective at intercepting most of the direct sunlight that hits it. All components of Manzanillo anatomy (bark, foliage, fruit, twigs, etc.) exude large amounts of caustic, white latex when injured. The waxy leaves (6 cm by 3.5 cm) are simple and alternately arranged. Mostly elliptical in shape (their widest point is shifted proximally from center), the glossy blades sport prominent, yellow mid-ribs and long petioles (3 cm). Manzanillo trees shed some of their leaves just before and during the early dry season (December and January) and maintain thin crowns during these months. By late February and continuing into March – in anticipation of the approaching rainy season – new leaves are generated and full, fresh Manzanillo canopies are in evidence along the beach by late April or May. Manzanillo trees possess strikingly vivid, green crowns at this time, and stand out from a background of otherwise withered, dry season vegetation.
The imperfect, petalless flowers are borne on long, axillar, green spikes (7 cm). Female blossoms (3 mm) consist of bulbous, maroon ovaries topped by split, star-shaped stigmas. Even simpler, male flowers (1 mm) sport several tiny, yellow-anthered stamens. Spatially separated along the spike, female blossoms – numbering only one or two – are located basally while the more numerous male flowers are positioned in clumps occupying the remainder of the inflorescence. Blossoms appear sporadically all year long, but most profusely during the March growth surge. Fruits are glossy green, apple or tomato-shaped orbs, averaging about 4 cm in diameter. A thin covering of toxic green or pale yellow flesh conceals a woody core whose several sections contain 4 or 5 rounded, tan-colored seeds (8 mm). Manzanillo fruits are present at all times during the year, but most abundantly during April and May when they fall from the trees in such numbers that they literally carpet the sand and fill the air with a sharp, fruity odor. Though they may look appetizing and edible, these fruits are not – sharing abundant amounts of caustic, burning, and poisonous sap with the leaves and twigs of this species. Allen cautions that the sap causes severe swelling, blistering, burning and inflammation. If contact is made with the eyes, it may cause temporary blindness. Seeds germinate with the first drenching rains of May or June, becoming beachside seedlings 5 cm tall.
Similar Species: In their particular habitat, Manzanillo trees are easily recognizable for their glossy, elliptical leaves possessing prominent yellow midribs. The omnipresent green globular fruits are a further aid in the identification of this important species.
Natural History: Manzanillo flowers are pollinated by bees and other insects. Fruits, though poisonous to humans – and perhaps all mammals – are eaten by certain reptiles: most notably the garrobos that inhabit these beaches and sometimes live on the Manzanillo limbs themselves. These omnivores swallow the fruits whole, digesting the fruit but passing the woody core intact.
Manzanillo is one of the few plant species that is able to survive the harsh conditions typical of the beachside environment. Here, it must endure drought-prone, sandy soils, high salt concentrations (including the periodic inundations of ocean waves), onshore gales from violent, offshore storms, and unchecked, searing, tropical sunlight.
Certainly, the impermeable layer of wax that covers Manzanillo foliage helps the tree conserve water during the long dry season. The thick, poisonous sap that is present in the leaves probably serves as a defense against defoliating, mammalian herbivores – like howler monkeys. Interestingly, the flush of fresh, new foliage that occurs in February and March precedes the wet season by one or two months. The presence of bright, shining, glossy-green Manzanillo trees along the desert-like beach of summer – when most other plants in this environment are bare, sun-damaged, and desiccated – is an impressive and welcome sight and that attests to the resilience of this species. Traditionally, people of the area have recognized this surge of growth as a harbinger of the rains to come. It is also viewed to coincide with – and be in celebration of – the March 19th holiday of San Jose Day.
Finally, as is the case for the Amapola and Almendro trees, Manzanillo’s ability to survive toppling enables it to cope with its unstable, coastal habitat. At the same time, falling toward the beach brings the crown out of the forest shade and into the abundant sunlight found nearer to the ocean’s edge.
Uses: Though the Manzanillo tree provides welcome shade to the starkly sunny and sultry places where it is most needed – and where few other plants could – this relief from the tropical sun is dangerous to take advantage of. Tiny droplets of sap often rain down from Manzanillo leaves and twigs and can severely irritate the eyes and skin of people lying underneath them.
Allen (1956) says that the wood of this species is yellowish-brown and that it has been used since colonial times for making fine furniture, but that it must be worked with caution – owing to the poisonous sap. He also notes that burning the wood is also not possible, for it produces a smoke that is a strong eye irritant.
Distribution: Manzanillo, exclusively a beachside tree, is found along both of Costa Rica’s coasts. The tree is often felled because of its poisonous nature and its numbers are rapidly diminishing. The species ranges from Mexico and the West Indies through Colombia.
Trees of Costa Rica's Pacific Slope 