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Dendrobium (den-DROH-bee-um) is a family of over 1000 species. It is a very diverse genus of orchids with many different cultural needs. The shape and form of their stems and leaves vary tremendously and the plants range from tiny in size to very large. Because of the extreme diversity of Dendrobium the following has been categorised by culture according to the popular main types.
2. Australian type
3. Spatulata (Antelope type)
6. Formosae (Nigrohirsutae Type)
These are some of the easiest Dendrobiums to grow. Their flowers are showy with colours: red, pink, orange, yellow, gold, purple, white etc., and the lip is often beautifully marked in contrasting colours. Nearly all are sweetly scented.
The heavy summer cloud cover indicates that some shading is needed from spring through autumn, but light should be as high as the plant can tolerate, short of burning the leaves. Light is high enough when leaves are slightly yellow.
Grow warm during the summer, cooling down in autumn From November – February: grow cool. Daytime temperatures can drop to 10°C (50°F) while night time temperatures can drop to 8°C (47°F). In winter the nobile type enjoy a rest but plants are healthiest if in winter they are allowed to become somewhat dry between watering but do not remain dry for extended periods. During their growing period they enjoy copious amounts of water in free draining compost.
Dendrobium kingianum or near relatives are the easiest to grow. The flowers appear in late winter/early spring. New plantlets or keikis may sometimes appear. These can be removed and potted separately after they have developed good roots (2.54cm long).
For their culture give intermediate to warm temperatures during their growing season and water generously from spring to autumn. In winter Den. kingianum enjoy a rest but plants are healthiest if in winter they are allowed to become somewhat dry between watering but do not remain dry for extended periods. A few cold weeks in winter to 8°C (47°F) will encourage flowering.
SPATULA (ANTELOPE TYPE)
These are evergreen for several years, range in size from medium to large and are normally vigorous with very long-lasting flowers in summer mainly but can flower several times a year.
These enjoy being warm all year long with night-time 16 to 18°C (60F-65°F) and day-time 24 to 32°C (75F-90°F). This type require no rest period and prefer medium to high light.
PHALAENANTHE (PHALAENOPSIS TYPE
These Dendrobiums are evergreen for several years. They are compact in size to quite large depending on species involved. Through hybridizing this type can flower two to three times a year and are long lasting flowers.
Grow warm all the year round with night-time 16 to 18°C (60F-65°F) and day-time 24 to 28°C (75F-82°F). Water and fertilise copiously when roots appear on new growths. They enjoy intermediate light levels. When new growth is completed reduce the water and fertiliser, give a 3-4 week rest cooling down to about 13°C (55°F). After this period warm back up to minimum 16°C (60°F) and another growth may appear and mature during winter for flowering in spring. This type of Dendrobium grows really well with Phalaenopsis but with higher light. If these are kept to cool they will drop their leaves!
These are evergreen for several years. This type of Dendrobium is medium size to large and are normally quite vigorous with flowers often lasting 4-5 months.
Culture is the same as the Spatulata (Antelope type) but with slightly cooler and drier in the winter.
FORMOSAE (NIGROHIRSUTAE) TYPE
These have cane like pseudobulbs covered in fine black hairs as well as some of the backs of the leaves. The flowers are normally white with orange in the lip, yellow or green/white and can be up to 10cm (4”) across. The flowers are long lasting – 2 to 3 months.
They require intermediate to cool temperatures year round, 10 to 16°C (50F-60°F) at night and 24 to 29°C (75F-85°F) day. Give plenty of water and fertiliser while growing but they enjoy a slight short rest (slightly cooler and drier) once the growth is completed. Keep just barely moist until new growth and/or flower buds appear.
Culture information taken from the Growers and Buyers Guide to Orchids in the UK – 2013 (Golden Guide).
Photographs supplied by S. Pask unless stated.