Dendrobium pleianthum Schlechter
Neville H.S. Howcroft

INTRODUCTION: :This orchid was collected during my recent trip to Mendi. The species is growing in a large colony on an embankment above the road near a river between Buiyebi correctional institute and Mendi and all the plants were in full bloom. It is included here because it is a common orchid from 500 metres altitude to around 2,000 metres altitude and in the past has been referred to incorrectly as Dendrobium bambusifolium.

DESCRIPTION: Plants epiphytic and terrestrial, erect to suberect with many stems, 90 - 150 cm tall; rhizomes short; roots glabrous; stems simple, slightly compressed, with many leaves throughout length. Leaf erect to slightly drooping, linear- lanceolate, subacute, apex unequally bilobed, smooth, texture leathery, 13-20 cm long, middle section 0.8-1.5 cm wide, base sheathing and amplicaul. Inflorescence a short, laterally compressed, conical, sessile rhachis, 0.2 - 0.4 cm tall, bearing 4 - 10 flowers on slender pedicels. Flowers erect to patent, not alway opening widely c. 1.5 - 2.4 cm across; dorsal sepal oblong- lanceolate, subacute, glabrous, c. 1.1 - 1.4 cm long, at base c. 0.6 cm wide; lateral sepals slightly shorter, falcate, acute, broad at base; petals obliquely linear - ligulate, subacute, narrower towards the base; labellum cuneate, above the middle half trilobed, c. 6.5 - 10 mm long,

DRAWING: Dendrobium pleianthum Schlechter
drawn by Neville H.S. Howcroft

DISTRIBUTION: This species appears to be only recorded from Papua New Guinea. However, it is such a common plant throughout many parts of the Highlands that it should be expected to occur throughout many parts of New Guinea and may have been described under another name.

HABITAT: A mountain species which seems to prefer mostly exposed situations growing in forest areas on trees, in secondary regrowth it grows as a terrestrial in peat, and in the montane and upper montane regions it grows on the edge of Oak forests as a terrestrial, in the Highlands it may be found near marsh areas and on old land slips and road cuttings growing as a terrestrial. Its altitudinal range is from 500 to 2,500 metres above sea level.

NOTES: The species belongs to a monotypic section named Pleianthe. It is related to the section Grastidium. The main difference is the peculiar inflorescence which is conical and produces many more flowers than those of the section Grastidium which only produce flowers iin pairs or in threes.

This orchid is an important source of dried golden yellow fibre material and cylindrical segments to the Highlands people for making ornaments such head and arm bands and necklaces.

The species is quite attractive when producing a massed display of flowers which are pleasantly but faintly perfumed. The longevity of the flowers is not known. It could be short as is mostly the case with orchids related to the section Grastidium.

CULTIVATION: An easy plant to grow as a terrestrial if you live in the Highlands. It should be a relatively easy plant to cultivate as an exotic with Cymbidium orchids.

CONSERVATION: To date I have not encountered any populations that can be considered threatened and therefore no conservation measures are recommended.