Costus from Cabo Matapalo

In July 2005, Reinaldo Aquilar and I visited a site on the southern tip of the Osa Peninsula in Costa Rica where we found an unusual looking Costus growing in sandy soil at the edge of the beach. This plant closely matches the description of a Costus that is mentioned under Costus comosus in the recently published Volume II of the Manual de Plantas de Costa Rica. It has previously been documented only on the Isle of Cano, located a few miles off the coast of the Osa Peninsula. "Mucho material proveniente de la Isla del Caño incluido aquí, que presenta hojas hirsutas, vainas más bien puberulentas y brácteas verdes en vez de rojas, parece ser intermedio entre C. comosus y C. villossisimus.

We found several large patches of this Costus in a very limited habitat at the junction of a steep rocky slope with the sandy soil of the beach. When we searched the area farther up the slope we did not find any of these plants. We were told by a local resident that he has observed that this Costus is occasionally washed away by the sea when there is a strong storm, but that it later resprouts and returns vigorously. The area, as you might expect is in strong sun during part of the day, but is shaded by the trees growing up on the slope during part of the day.

The following is a detailed description of this Costus with photos and some comparisons to the description by Maas in Flora Neotropica. Also for comparison, below is a photo of the plant that has been identified as Costus comosus that is in cultivation in the United States. When I first saw our new Costus I did not recognize it as Costus comosus, because the plant in cultivation so named looks VERY different. It has bright red bracts with red appendages ascending, the leaves are much broader and it is a more compact growing plant.
Costus comosus in cultivation in USA

Root system: When Reinaldo collected a specimen plant, we very carefully dug deeply around the plant to see if there might be root tubers or other unusual structure to the rhizome and root system. We did not see any root tubers but the root system itself was massive. (need to add Reinaldo's photo of the roots). The rhizomes produce closely spaced leafy stems and the patches we found of this Costus measured 3-4 meters in diameter.

Sheaths: To about 2 meters tall, 1.6 cm in diameter at base, brown to tan, papery, twisting then green where leaves begin and with a velutinous covering (using Maas' definitions of hairiness). Maas description of C. comosus matches this.

Ligule: Very short, 1-2 mm, truncate, green, velutinous like the sheaths but with arachnoid fibers extending from the margins. Maas description of C. comosus matches this.

Petiole: About 2 mm long, green, velutinous like the sheaths. Maas description of C. comosus matches this.

Leaves: Mature leaves 25-27 cm long and 5.5 to 6.5 cm in width, undulating margins, cordate base, acuminate apex with acumen 6-8 mm in length, green, velutinous on both sides. Maas description of C. comosus closely matches this except for the cordate leaf base.

Inflorescence: Cylindric, to 12 cm long by 3 cm in diameter. Apex of inflorescence is distinctive with young foliaceous appendages forming a floret at the top. Propagules had formed from several of the mature inflorescences. Maas description of C. comosus matches this.

Flowers: Yellow, tubular with tightly closed labellum and stamen, about 2.5 cm in length.

Bracts: Green, 1.5 cm in length by 2 cm in width with a few short hairs near the base. No hint of reddish coloration on the bracts or the bract appendages. Maas description of C. comosus matches this - bracts red or green.

Appendages: Green, foliaceous, acutely triangular, sharply folding down from the bracts, sparsely puberulous. Maas description of C. comosus differs here, describes them as red except for basal ones, and horizontal or ascending - not pendent as they are in this plant.

Bracteoles: Whitish to pale green with red at apex, boat shaped, 1.5 cm long by .5 cm wide, apex turned up sharply, sparsely puberulous especially near the base and the apex. Maas description of C. comosus matches this except for the color.

Calyx: Pale green with reddish lobes, deeply lobed, lobes trianugular, overall 1 cm in length by .7 cm in diameter, sparsely puberulous at base and apex like bracteole. Maas description of C. comosus matches this except for the color.

Corolla: Yellow, glabrous, center lobe 2.5 cm long by 1.2 cm wide. Corolla is nearly as long as stamen and labellum and folds tightly around them. Maas description of C. comosus matches this.

Labellum: Yellow, glabrous, about 2.5 cm in length, typical 5 lobed with lateral lobes deeply incised. Labellum closed tightly over stamen in mature fresh flower. Maas description of C. comosus generally matches this.

Stamen: Yellow, glabrous, base fused to labellum, about 2.5 cm long. Apex triangular, thecae 4 mm, placed 3 mm from apex of stamen. Maas description of C. comosus generally matches this.