The green and brown pattern playing vertically along overlapping triangular spikelets makes this the most beautiful sedge inflorescence I have yet seen.
Cyperus trachysanthos is a perennial, rhizomatous species of sedge. The densely-growing culms (the above-ground stems of a grass or sedge) are triangular in shape and can reach a height of 45 cm. The leaves are slender and coated with a sticky wax, giving Cyperus trachysanthos its common name of sticky flatsedge. The inflorescence is quite striking. It is composed of a few heads, each with up to 30 spikelets. The 20 cm spikelets have up to 20 flowers that are covered by yellow-brown glumes (outer sterile husks).
David Eickhoff, the photographer, writes that this photo was taken along the Lower Kamananui Stream in the Waimea Valley of O’ahu. He explains that this specimen was “probably an escapee from the upper man-made ponds where it is planted.” Cyperus trachysanthos is endemic to the Hawaiian Islands. It is an endangered species. A US Fish and Wildlife Service 5 Year Review (PDF) found that there were only two populations of Cyperus trachysanthos with over 50 mature individuals. Efforts are being made to restore sticky flatsedge to parts of its range where it is no longer found. New populations are also being established on suitable sites. If some of these new populations are spreading downstream, this is good news indeed.
Cyperus trachysanthos is gaining popularity among Hawaiian gardeners. Hawaiian nurseries that stock this species recommend gardeners plant it in moist areas or around water features. Sticky flatsedge can be used for mass plantings. It also makes a great accent, particularly if planted among ground-covers or rock features. The inflorescence purportedly makes a fabulous addition to floral arrangements.