Flora of Barro Colorado Island

Zanthoxylum panamense

P. Wils., Contr. U.S. Natl. Herb. 20:479.1922

Arcabú, Acabú, Alcabú, Prickly holly, Prickly yellow, Lagarto

Medium to large, dioecious tree, to 28 m tall; trunk to 75 cm dbh, buttressed to ca 1.5 m, armed, the prickles conical, corky, the base to 3.5 cm long, the apex some­what flattened laterally, deciduous from older trunks at base, persistent above and on branches (especially the smaller ones); outer bark thin, not deeply fissured, often very roughened; inner bark thick, tan, granular, flaking upon slash; twigs puberulent, the trichomes appressed or uncinate; sap usually bitter, not noticeably aromatic. Leaves alternate, compound, imparipinnate or rarely paripinnate, mostly 15-60 cm long; petioles minutely puberulent, mostly 3-9 cm long, the basal pulvinus pro­nounced; rachis often canaliculate above, broadly so below leaflets, glabrous to minutely puberulent, some­times armed; petiolules 3-5 (7) mm long; leaflets 10-20, opposite to subopposite, sometimes alternate especially basally, mostly ± oblong-elliptic, abruptly acuminate (the acumen sharp or blunt), rarely rounded at apex, rounded or cuneate and usually inequilateral at base (except terminal leaflet), 4-19 cm long, 1.5-7 cm wide, entire or obscurely crenulate, glabrous above or incon­spicuously puberulent especially on midrib, glabrous or with inconspicuous, short, appressed trichomes below, occasionally bearing 1 or more, long, sharp prickles on midrib beneath-, both surfaces shiny, with small and numerous pellucid dots (sometimes obscure before dry­ing), sometimes with a few much larger, plate-shaped glands on both surfaces. Panicles terminal, 20-30 cm long (shorter on pistillate plants), highly branched, the branches densely hispidulous; pedicels ca 1 mm long; flowers unisexual, white or greenish, 5-parted; calyx puberulent, the lobes short, acute to rounded; petals ± elliptic, acute at apex, 1.5-3 mm long, to 1 mm wide; staminate flowers with stamens 5 exserted, the filaments ca 3 mm long, alternating with lobes of pistillode, the anthers oblong, the pistillode minutely pubescent; pistil­late flowers lacking stamens, the ovary broadly obovoid, 3-or 4-lobed, to 1.5 mm long, glabrous and glandular-­dotted, the styles (2) 3, the stigmas broadly discoid, nearly sessile, round or obtusely 3-sided, more than three-­fourths as broad as ovary. Fruits of usually 3 or 4 brown follicles, each 6-8 mm. long, puberulent, dehiscing from an apical, medial suture, the valves persistent; seeds 1 per follicle, shiny, black or dark brown, 3-5 mm long, suspended from capsule on a tough fiber. Croat 6249 and 12574 (large-leaved form), 14885 and 16589a (small-­leaved form).

Occasional, especially in the young forest. Flowers from April to October, mostly from June to September; plants may flower only once every two years. The fruits mature mostly from June to December. Plants have been seen replacing their leaves over a short span of time in the late dry season.

Probably the most variable Zanthoxylum on the island, especially in terms of leaf shape. Some BCI plants have consistently much smaller leaflets than others, and addi­tional morphological and phenological study may show them to be distinct species. Plants of the small-leaved form generally flower and fruit ahead of those with larger leaves, although the seasons overlap. This is further evidence that two taxa may be involved in what is being called Z. panamense. The small-leaved plant corresponds with the type.

This species and Z. setulosum are different from Z. procerum in their manner of dehiscence. The fruits of Z. procerum expel their seeds from the follicle by the elastic movements of the inner wall of the carpet, whereas Z. panamense is thought to be bird dispersed because of the shiny black seeds displayed outside the valves on a slender fiber.

The prickles on the trunk may be hollow and are often inhabited by ants.

Costa Rica and Panama. In Panama, known from trop­ical moist forest in the Canal Zone, Bocas del Toro, Colon, Chiriqui, Panama, and Darien.

See Fig. 297.

Photos from STRI Digital Archive

  • Zanthoxylum panamense immature-fruit
  • Zanthoxylum panamense immature-Infructescences
  • Zanthoxylum panamense immature-fruit plant
  • Zanthoxylum panamense immature-fruit
  • Zanthoxylum panamense immature-Infructescences
  • Zanthoxylum panamense immature-fruit plant
  • Zanthoxylum panamense
  • Zanthoxylum panamense
  • Zanthoxylum panamense Leaf
  • Zanthoxylum panamense Fruit