I have seen this Costus growing in conservatories in Atlanta, the Smithsonian Institution, Fairchild Gardens, Tom Wood's greenhouse, at Enid's Natural Selections Exotics, John Banta's place, and in my own greenhouse, but I had never seen it in flower or even seen photos of it in flower. Last week Ray Baker and I were checking id's on his Costaceae at Lyon Arboretum in Hawaii, and look at what we found. He said in all the years it has been there at Lyon he had not seen it in flower. It is really spectacular, but a bit difficult to grow and evidently very shy to come to flower at least in cultivation. Fortunately it is a beatiful plant even without the flowers, but look at this!
One of the major ways that Costus species are differentiated is whether or not they produce "leafy" appendages to the bracts. Costus comosus and Costus productus also produce red bracts with red appendages, but quite different in shape and quite different in texture. The flowers are also different - tubular vs. open and spreading. That is another major characterisic to distinguish Costus species. The tubular flowers are pollinated mostly by hummingbirds wheras the open type is pollinated by bees.
The photo below shows the red bracts with red appendages more clearly.