Bulbophyllum himantosepalum

I purchased this plant as Bulbophyllum potamophilum from Far East Agriculture in May 2017.  It is obviously incoorect when you compare it to the illustration on Orchids of New Guinea web site.  It matches well to the illustration of B. himantospealum.  Indeed, many photos of B. potamophilum on internet are actually from B. himantosepalum, and I haven't seen a single photo of correct B. potamophilum yet. It is a fairly recently described species (Vermeulen & Sieder 2015), and there isn't much information available. Since the original description is based on a plant cultivated at Universität Salzburg Botanical Garden, habitat information is not available, but it was supposed to be imported from Papua Province of New Guinea (i.e. Western half of Papua New Guinea). Orchids of New Guinea web site has the most information, and they states that it is cool growing.  However, I have been growing it fairly warm; max/min daily temperature is 27/18C (80/65F) in summer and 24/16C (75/60F) in winter.  It is located at the edge of the growing space, so it might be getting less than ideal amount of light, but it seems to grow ok with fairly low level of light.

Note the characteristic hook of the dorsal sepal.

The lateral sepal is removed to show the arrangement, of petals  and lip.

Column and lip.  The dorsal sepal, the petal and lateral sepal are removed.

Column, the bottom side.  The lip is removed.

Column, the top side.

Disected flower.  The ruler is metric, so each increment is 1mm.  The top side of the lateral sepal and petal is showing the abaxial surface (toward the ovary), and the bottom sides are showing the adaxial surface (toward the column).  The lateral sepals are pretty fleshy, and thicker than you imagine. 

The dorsal sepal is strongly folded along the midnerve, and I couldn't flatten it, so it is showing the side view.  The right petal is showing the adaxial surface, and the left petal is showing the abaxial surface.

Literature Cited:

• Vermeulen, J. J. and A. Sieder. 2015. Three new species of Bulbophyllum from Indonesia.  Malesian Orchid Journal 15: 39-45.