Costus is a member of the Zingiberaceae (Ginger) family which is grown in tropical areas across the globe. It is often called 'Spiral Ginger' because the new stems grow in a spiral with the leaves on the outer side of the curve.
The spear-shaped leaves are soft and hairy with a velvet-like feel to the underside. Just last year, the genus Costus was divided into four new genera based on study of DNA makeup of the plants.
Costus speciosus (Crepe Ginger), now called Cheilocostus speciosus, grows a red cone-shaped 'head' (bract) at the top of the stalk from which one or two large white flowers emerge from the lower part.
As each flower dies, another one will follow slightly higher up the bract for a period of up to a month after which the head browns and eventually falls off the plant.
The plant is tall, 2-3 meters (6-10 ft.), and as new stalks emerge from rhizomes in the soil, it forms a dense clump, easily measuring 3-4 meters wide (10-13 ft.). The plant can become invasive if not controlled.
We recently dug up/cut back/thinned out two large clumps of this Costus. This picture shows one of the clumps back in June 2006. It was much larger than this when we started.
This picture shows the result about three weeks after we 'reduced' it. It seems to return from every piece of rhizome left in the soil − we did try to remove all of them!
I think that I will (be trying to) remove all of this plant from my garden. It grows to the perfect height for the flowers to show from our sala familiar (family room) windows, but it just seems too invasive.
We have another wild species which grows a lovely, tight, orange cone-shaped bract, many of which have two heads. We found this one growing by the creek in heavy shade but surprisingly, it is much more well-mannered than the Crepe Ginger that we bought at a nursery here in Honduras.
This one grows to a height of only about 1-1.2 meters (3-4 ft.), has shorter, wider, slightly variegated leaves, and doesn't spread as aggressively, staying in a bush-sized clump.
I believe this one to be Costus scaber, in which the bract colors can vary from yellow to orange to red. It is native to many parts of Central America.
Costus scaber can be identified by the single row of upright hairs growing on the upper part of the leaf vein. In three years, we have never seen more than the tiniest blooms peeking out of the bracts, but the orange cones are attractive even without the showy flowers.
Aloha Tropicals lists 45 varieties of Costus, with flowers of white, red, yellow, orange, and pink, and different variations of leaf size and color, and Dave Skinner (who must be The Ginger Expert) at GingersRUs displays hundreds of Costus pictures. Click on the "thumbnail image pages" button on the left hand side of his home page to view eight pages of Costus photos.
Costus are easily propagated by divisions or stem cuttings and quickly form a nice bushy clump which flowers year round here in the tropics. They grow in sun, partial shade, and even deep shade as their natural habitat is the forest floor.