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Dendrobium Sw.

den3.jpg - 17Kb Dendrobium (den-DROH-bee-um)

Subfamily: Epidendroideae

Tribe: Dendrobieae

Subtribe:Dendrobinae

There are about 900 species, in India, China, S.E. Asia, Japan, Malaya, The Philippines, New Guinea, Australia and the Pacific Islands including New Zealand.

The name is derived from the Greek dendros (tree)and bios (life), referring to the aerial epiphytic existence of most species. Dendrobium was established by O. Swartz in 1799 in Nova Acta Societatis Scientorum Upsaliensis p.82. It does not make good reading as it is in botanical Latin!

Dendrobium is a diverse genus of orchids with different cultural needs. Many go througha growth phase and then a rest phase during the course of a year, and must be given water and temperature to match these periods of growth and rest. Flowers can last one day to many weeks, depending on the type. Owing to the extreme diversity of the genus, there are about 10 main groups; the writer has categorised culture according to the following main types as found in amateur houses:

PHALAENANTHE

Evergreen for several years, with thin, tall pseudobulbs, terminal inflorescence (flower spike at top of cane), usually appearing in the autumn or twice a year (see culture). Species such as Den. affine, Den. bigibbum (phalaenopsis), Den. dicuphum and Den. williamsianum.

CULTURE

Grow warm all year round; 60F nights; water and fertilise heavily when roots appear after growth finishes. If a short cooler (55F) dry rest is given, then the plant may be ready for another growth, which may mature during winter and flower in the spring. Treat this growth as a summer growth cycle. These grow well with phalaenopsis, except for the rest period. Plants will go deciduous if grown too cool and dry.

SPATULATA (Antelope type)

Evergreen for several years. Most are large, vigorous plants with long-lasting flowers in summer to several times a year. Species such as Den. antennatum, Den. canaliculatum, Den. discolor, Den. gouldii, Den. johannis, Den. lineale (veratrifolium), Den. stratiotes, Den. strebloceras and Den. taurinum.

CULTURE

Warm all year (60 to 65F nights, 75 to 90F days); no rest period; can be kept cooler in winter if dry; medium to high light.

DENDROBIUM

Most of the plants are pendulous, with leaves all along the canes that most often drop with onset of cooler, drier weather. One to five flowers per node are borne from the nodes of the leafless canes in mid-winter through to early spring.

GROUP 1

Species such as Den. chrysanthum, Den. friedricksianum, Den. nobile including varieties, (of which 11 have been described in a Victorian orchid book) and wardianum.

CULTURE

Growth period in summer; give warmth, water and fertilise heavily from when roots appear until top leaf appears on canes. Then give high light, no water, or fertiliser, cool nights (40 to 50F). In other words, forget about them. I had a plant of Den. Nobile var.cooksonianum (the peloric form), which was put on a high shelf for its winter rest. Totally forgotten and discovered 6 months later, still green but very shrivelled. It was watered and the canes plumped up and the plant flowered extremely well.

GROUP 2

Species such as Den. anosmum (superbum), Den. crassinode, Den. falconeri, Den. fimbriatum, Den. findlayanum, Den. heterocarpum (aureum), Den. loddigesii, Den.moniliforme, Den. parishii, Den. primulinus and Den. transparens.

CULTURE

Same as Group 1, but winter nights 55F. Deciduous species need virtually no water or feeding in winter, and maximum winter light.

CALLISTA

Most are pseudobulbous plant with pendant inflorescences.

Pictured above is Dendrobium thyrsiflorum as grown by the author. The plant can be found in N.E. India, Burma, Thailand and Laos at altitudes of between 1100-2300m (3630-7590ft.) or higher. Hence it can be grown well in the cool house.

Species such as Den. aggregatum (now properly lindleyi), Den. chrysotoxum, Den. densiflorum, Den. farmeri and Den. thyrsiflorum. Some of these look and grow well mounted on bark, but some only last 7-10 days in flower.

CULTURE

Summer give warmth (60-90F), medium light, medium quantities of water and fertiliser. Winter keep cool (50F) nights, medium light, just enough water to keep pseudobulbs from shrivelling, no fertiliser.

LATOURIA

Leaves at top of pseudobulbs are large and leathery, inflorescence erect, flowers commonly yellow-green. Species such as Den. atroviolaceum, Den. macrophyllum and Den. spectabile. Generally long lasting flowers, especially atroviolaceum.

CULTURE

Same as antelope types, but cooler and drier when resting in winter.

FORMOSAE (Nigrohirsutae Type)

Canelike pseudobulbs, with black hairs on leaf sheaths and pseudobulbs often apparent, leading to the popular name nigrohirsutae. Flowers usually white, up to 4 inches across, two to three together from near the end of the pseudobulb. Long lasting. Species such as Den. bellatulum, Den. dearii, Den. draconis, Den. formosum, Den. infundibulum, Den. lowii, Den. lyonii, Den. margaritaceum, Den. sanderae and Den. schuetzii.

CULTURE

Intermediate to cool all year round, 50 to 60F nights, maximum 85F days. Water and fertilise when growing; give a slight short rest (dry) when growth is completed. Keep barely moist until growth starts again. New growths are prone to rot if kept wet. Most new growths, in general, are like small funnels, which trap water. Beware of this.

What plants need is good air movement at ALL times. Use large oscillating fans, like ones used in offices. Just be careful with water and keep them on constantly. The airflow should give the plants slight movement and a reduction in fungal and related diseases. When mentioning fertilising heavily, don't add a lot of feed at one watering. Fertilise 3 times in 5 at half strength as stated on the container. Use high nitrogen feed from spring (or start of growth) to August, and then use high potassium feed. Stop feeding in winter when growth has finished or flowering has stopped. Use any type of fertiliser. There is no secret or special formula to feeding orchids. Please try growing some Dendrobiums. They are well worth it.

Peter Fowler

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