The genus Bulbophyllum is one the few which occur in the Old and New World. The species of the Section Macrobulbon are however only to be found an the island of New Guinea. They are - in foliage and flowers - among the largest in the genus.

History of Taxonomic Identification:

The first species in this genus, Bulbophyllum macrobulbum, had been collected in 1910 during the first Lorenz-Expedition and was described by J.J.Smith, in Bull. Dep. Agric. Indes. Nederl. XXXIX, (1910), 4, referring to a plant cultivated in the Botanic Garden at Buitenzorg. Rudolf Schlechter, during his evaluation of the Orchideen von Deutsch Neu Guinea (The Orchids of 'German New Guinea), defined in 1913 the section Macrobulbon based an this species.

In 1914 Bulbophyllum fletcherianum followed, described by Pearson in the Gardeners Chronicle, Serie 111. LV, 320 (1914). The plant described was given as originating from Hollandia, then capital of Dutch New Guinea without any details of its real origin.

In 1937 J.J. Smith described Bulbophyllum phalaenopsis, in Bulletin du Jardin Botanique de Buitenzorg, Serie 111, vol. XIV 1937, 165, recording the plant as coming from the Siriwo River in New Guinea.

No further species were described until 1990, when L. A. Garay, F. Hamer and E. S. Siegerist described Bulbophyllum spiesii in The American Orchid Society Bulletin, 59: 810 - 812 from the vicinity of Bololo, New Guinea, using plants which had been erroneously identified as Bulbophyllum fletcherianum.

The same three authors in 1992 published in Die Orchidee, Heft 3, 139, the description of Bulbophyllum cruentum from the Baliur River, New Guinea. Followed by Bulbophyllum orthosepalum J.J. Vermeulen, published in Blumea, Vol.38, No.l, 1993, 146, the plant came from Papua New Guinea, Central Province, Efogi.

The description of Bulbophyllum agastor  Garay, Hamer et Siegerist, followed in 1996 - published in Lindleyana, 11 (4), 224, origin Papua New Guinea: Southern Highland Province, Mendi, 5200 ft. Bulbophyllum hashimotoi Yukawa & Karasawa was described in 1997 in Ann. Tsukuba Botanical Garden 16:17-24,1997.

Bulbophyllum hashimotoi however was not included in the contribution of Yukawa & Karasawa. This species is regarded by Dr. Leslie A. Garay and many others as a synonym of Bulbophyllum orthosepalum J.J. Vermeulen.

Characteristics of Section:

Mostly large, often wrinkly, brownish to reddish pseudobulbs, often large (up to 120cm), drooping leaves. All references to leaf length differ very much in the available literature. So far the plant in the collection of the Botanic Garden in Vienna have reached lengths up to 75cm. Flower inflorescences short, 2 to 20 flowers, the lateral sepals usually fused, often elongated. The flowers usually exude a putrid smell.

Characteristics of Species:

B. agastor: petals with wavy rims, flowers like B. cruentum, differently colored, lip callus not hirsute, flowers with different proportions, lateral sepals fused, only at the basis free.

B. cruentum: petals with wavy rims, flowers as with B. macrobulbum, but much smaller, differently coloured, fewer flowers, labellum with short hairs, petals not fused.

B.fletcherianum: petals not wavy, 5-8 red to dark red flowers with white markings, lateral sepals much longer than the dorsal sepal.

B. macrobulbum: petals with wavy rims, flowers white-yellowish with red markings, lateral sepals not much longer than dorsal sepal, lateral sepals fused almost to the tip.

B. orthosepalum: petals with wavy rims, flowers like B. cruentum, flowers more rounded and closed, lateral sepals fused an the inner, lower rim, an the upper, outer rim fused up to a third of their length. B. phalaenopsis: petals not wavy, up to 11 flowers, lateral sepals not as elongated as with B. fletcherianum, sepals hirsute an the outer side.

B. spiesii: petals not wavy, up to 20 flowers, much smaller and partly with different shape as with B. fletcherianum. While Yukawa & Karasawa regard B. spiesii as a synonym for B.fletcherianum, the author follows Dr. Leslie A. Garay, who treats both as separate taxa.

The following key has been newly defined to identify the species of the section Macrobulbon

Key for Bulbophyllum Section Macrobulbon - partly based an data by Yukawa & Kurasawa

1. petals with wavy rim, lateral sepals shorter than 60 mm, therefore not much longer than the dorsal sepals; the flower appears therefore not elongated but more     rounded...............................................=4

1a. petals with smooth rim, lateral sepals longer than 60mm and much longer than the dorsal sepals.................................................................=2

2. sepals hirsute an the outer side.... B. phalaenopsis 2a. sepals not hirsute an outside.............. ............ .=3

3. five to eight flowers per inflorescence, lateral sepals 9 to 10cm Iong.................... B. fletcherianum

3a. up to 20 flowers per inflorescence, lateral sepals up to 7cm long........................................... B. spiesii

4. lateral sepals free, flowers dark red, labellum hirsute..................................................B. cruentum

4a. lateral sepals partly fused ..................................=5

5. petals half as long as sepals, with leaves up to 80cm long .....................................B. orthosepalum


5a. petals up to two thirds in length of sepals.......................................................................=6

6. lateral sepals fused, except at tip, dorsal sepals approx. 40mm long............... ..... ....B. macrobulbum


6a. lateral sepals fused with exception at base dorsal sepal approx. 25mm long........................ B. agastor

Growth Habits:

B. cruentum grows as a terrestrial. All other species grow epiphytically an tree trunks. B. fletcherianum and B. macrobulbum also grow as lithophytes an steep cliffs. The reddish color of bulbs and leaves as well as the occurrences an cliffs are hints to a high tolerante to bright sunlight.

Cultural Requirements:

The collection in the Botanical Gardens of the University of Vienna contains B. cruentum, B. macrobulbum, B. spiesii, B. phalaenopsis and several unidentified plants which have not yet bloomed. The plants grow well under warm conditions with a minimum temperature of 22°C in the wintertime if placed in a bright place. During summer the temperature naturally rises muck higher. The plants are grown an "Sandwiches" of pine bark either horizontally or vertically.

Every morning the plants are watered heavily while the overall humidity of the warmhouse is maintained by a high pressure misting System. The misting system is controlled by a combination of time switches (minimal uptime 30 minutes) to maintain a humidity of 90%. During summer, when the ventilation panels are usually open and during the winter heating periods, the humidity level may fall, so that the control parameters of the misting System are adjusted accordingly. High humidity combined with a high rate of air movement and constant fresh air are the most important parameters for plant health and successful cultivation.

Fertilizing:

Plants which form such large bulbs and leaves during their growth cycle wilI need adequate feeding. In the Botanical Gardens the plants are provided with long-range fertilization using Osmocote which is placed an top of the bark Sandwich. In addition to that they are fertilized together with all other orchids once a weck with standard fertilizers at 1/4 of the concentration given for houseplants. The plants are usually rapid growers, a seedling which have been acquired from the German nursery Glanz in 1992 with a leaf length of approx. 5cm , now (1998) has leaves of 60 x 15cm and bulb diameters of 10cm, however they have not yet bloomed.

Pests:

So far there have been no problems with pests.

Propagation by division:

Back bulbs produce new growth without any problems.

Propagation from seeds:

Manual fertilization by selfing B. macrobulbum has been successful. Within 45 weeks seeds developed which had excellent germination rates. Manual pollination of B. phalaenopsis, B. spiesii and B. cruentum have so far been unsuccessful. Currently the Botanical Gardens cultivates seedling flasks of the following species: B. phalaenopsis, B. macrobulbum und B. cruentum.

Hybrids:

The Botanical Gardens also made a hybrid, which has already formed protocorms. It is Bulbophyllum lobbii (as the pod parent) crossed with B. spiesii. This cross has been made primarily to check whether species from different sections - in this case Macrobulbon and Sestochilus - can be crossed successfully. In addition the Botanical Gardens received a further hybrid of this group - Bulbophyllum "Magnifico"  which is Bulbophyllum Louis Sander x Bulbophyllum phalaenopsis.

Anton Sieder, Botanical Gardens, University of Vienna, Vienna, Austria

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