Xylopia sericophylla Standl. & L. Wms.

Common Name: YAYO

Common evergreen subcanopy or canopy tree (20-35 m). Yayo does not show a marked preference for any particular habitat or ecosystem, growing equally well under many soil and moisture regimes. The species is particularly notable for its perfectly cylindrical, slowly tapering, monopodial trunk and glossy, pale-green bark.

Description: Though Yayo is capable of growing to great heights - comparable to those of other tropical forest giants like Sloanea or Hymenaea - its trunk never attains wide girths and totally lacks buttress roots. It is not uncommon to see towering, pole-like trees that are 35m tall and yet only 60 cm in diameter at the base. Of all the tree species present in its habitat, Yayo has perhaps the most impressively and consistently columnar bole. Rising up through the understory, its unbranched and perfectly cylindrical trunk tapers very slowly to its apex. Yayo bark is characteristic as well, being thin, very smooth - even glossy - and pale green in color. Its surface is shallowly creased by vertical furrows. Branches, appearing only at the very top of the tree, leave the trunk at right angles and form a pyramidal, narrow crown. Leaves (11 by 3.5 cm) are simple, alternate, narrow and elliptical or slightly oblanceolate in shape, and possess small drip-tips. A fine, dark pubescence on twigs, petioles (4 mm) and leaf veins gives their surfaces a somewhat rough or sandpapery texture. Late in the wet season (October through December), a part of the old foliage - sometimes all - is shed. New leaves, strikingly pale green (or white) and limp, emerge within two weeks in tiers along the twigs. Flowers are creme-colored (4 cm), with six thick, fleshy petals and a central disk composed of hundreds of short, white stamens. The blossoms are borne directly from the leafless, woody, older portions of the horizontal branches - rarely are they seen mixed among the current foliage. Only faintly aromatic, they smell of lemon. Flowering periods appear to be highly sporadic with little synchronization between mature individuals, however most activity takes place between November and January. Fruits consist of green, spike-ball shaped structures, with each spike composed of a 3 cm long, club-shaped berry. About five of these clubs are attached to a common base which, in turn, is attached to the woody tree branch. Each berry bears one to three seeds (8 mm) embedded in a dark, slippery aril. Fruiting occurs shortly after flowering and primarily during the summer months of January through April.

Similar Species: Based upon leaf characteristics alone, Yayo could be confused with tens of other tree species present in Costa Rica. Fortunately, it's tall, cylindrical, monopodial trunk clad in glossy, pale-green bark is highly distinctive and identifying.

Natural History: Yayo's overall treeform is typical of a small group of tropical forest trees - usually canopy or sub-canopy species - that show a strongly developed main trunk that does not divide into secondary trunks and thick limbs. Instead, small branches leave at right angles to the single trunk high in the canopy, providing only a narrow, pyramidal crown. Compared to large-crowned, spreading species like Hymenaea, Ceiba, and Hyeronima this appears to be a disadvantage, since a smaller canopy of leaves reduces the amount of sunlight available to the tree. However, in a recent gale-force storm that pounded the Pacific Coastal area (Tropical Storm Gert), small-crowned species were spared much of the damage suffered by their larger contemporaries. Other trees that have similar monopodial trunks and pyramidal crowns include Virola koschnyi, Virola sebifera, Guatteria sp., Zuelania guidonia, Xylopia frutescens, Aspidosperma spruceanum, and Unonopsis pittieri.
A comparison of fruit positioning and coloration between different tree species can provide some interesting information regarding their seed dispersal strategies. For instance, Yayo places its dull-green fruits along the bare, thicker portions of the branches - far inside and away from the foliage cover. This is probably intended to make them more accessible and visible to the squirrels and bats that disperse them. Since most mammals are colorblind (primates being a notable exception), brightly hued fruits are would not be advantageous in this case.
In marked contrast, the Ormosia tree (Ormosia sp) (see description) makes its fruits highly visible to flying animals, holding its seed pods out in the open air above the tree crown. Etched with a bright orange color pattern, these seeds are probably intended to lure color-sighted avifauna to accomplish the dispersing task.

Uses: As suggested earlier, the neatly cylindrical, hard-wooded trunks of this species have potentiated their use as rollers in the grinding of grains.

Distribution: In Costa Rica, this species is native to the central and southern Pacific lowlands.

Trunk    Flower    Fruit   Fruit    Trunk