Comparison of Costus spicatus, spiralis, and scaber.
From Maas, Flora Neotropica, Monograph #8
C. spicatus C. spiralis C. scaber
Leaf upperside costa (midrib) strigulose to glabrous glabrous strigulose (rarely glabrous)
Bract color exposed part=greenish, covered part=reddish dark red orange-red to red
Bracteole length 17-30 mm 15-29 mm 9-12 mm
Calyx length 9-16 mm 7-12 mm 3-7 mm
Corolla length/color 40-50 mm / yellow to pink 45-60 mm / pinkish red 35-40 mm / orange to yellow
Labellum length/color 25-50 mm / yellow 25-30 mm / pinkish red 20-30 mm / yellow
Stamen length/width 30-40 mm by 10 mm 25-30 mm by 5-10 mm 20-25 mm by 6-8 mm
Stamen apex shape obtuse or rounded emarginate, rarely entire obtuse
Anther length 7-8 mm 7-9 mm 5-7 mm