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Welcome to the AOS Beginner's Newsletter. We will be sending you monthly tips on how to grow orchids and help you get them to bloom again. In addition to the information presented here, we invite you to visit the AOS website at www.aos.org and check out the information found under ORCHID INFORMATION > ORCHID BASICS.
"D" is for Dendrobium
"D" is for diversity
 Dendrobium is a vast and diverse genus of orchids found throughout Asia and the Pacific Islands. There is a species or hybrid for nearly every taste or growing condition. Depending on where you live, the most commonly grown types are phalaenopsis or nobile type hybrids. The first type was originally based on the species, Dendrobium phalaenopsis (named so because the flowers resemble phalaenopsis). That name is no longer accepted. The current name in use is Dendrobium bigibbum.
Shown at left is the variety known as compactum. This species from Australia and New Guinea contributes its flat, round form to hybrids. Twenty five years ago these orchids were traditionally fall bloomers. Nowadays the gene pool has become complex with many different parents in any give hybrid's family tree. That, coupled with modern, global commercial horticulture has made these popular orchids available nearly year round. Like phalaenopsis, talented breeders have created myriad colors, patterns, shapes and sizes within this group; there is literally something for everyone. With their long flower stems, "DenPhal" hybrids also make excellent cut flowers for making floral arrangements.
In its native habitat, Dendrobium bigibbum can be found growing on rocks in very bright light. Although we don't want to give our orchids the same harsh treatment they receive in nature, most DenPhal hybrids require somewhat brighter light than
phalaenopsis or paphiopedilum hybrids. You can refer to our November 2009 newsletter. Filtered light is just about right for DenPhals but most will adapt to brighter or shadier conditions.
The usual advice for these dendrobiums is to keep the pot size small for the size (height) of the plant. They have short rhizomes and fine roots that do not need large pots. Because the pseudobulbs, or "canes", are tall, plants in plastic pots can become top heavy and unstable, especially when in bloom. We like to use a few pieces of smooth landscape "river rock" in the bottom of pots to add stability. You can also nest blooming plastic-potted DenPhals in a large, heavier clay pot.
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| Den. Burana Stripe |
Den. Mini Diamond |
Den. Quique Ramirez |
Den. Global Village |
Like cattleyas, water plants when they are almost dry from the previous watering. Temperatures should be kept in the 60-90º F range although plants can tolerate cooler temperatures for short periods. If subjected to 50º F or below for more than a few nights plants may show their displeasure by dropping leaves over the following weeks. Any fast draining potting media will suffice for DenPhals and should be replaced every 2-3 years. Plants should be given less water and fertilizer in winter.
The other type of dendrobium popular in the trade is the "nobile dendrobiums" which are named after the species that figures in the background of the hybrids, Dendrobium nobile shown at right. Nobile dendrobiums can be very showy, producing clusters of colorful flowers along leafless canes in the spring. They are available in a wide range of colors but are usually some combination of white, yellow and orchid-lavender. Much of the culture information above also applies to nobile dendrobiums. The most important difference is that these dendrobiums
are deciduous and require a distinct winter "rest" period in order to flower
well. It is important to not fertilize them after night temperatures begin to
drop below 50-55º in the autumn. Watering should be kept to a minimum with just
enough given to prevent severe shriveling of the canes. This cool, dry winter rest will initiate bud development for a bountiful spring flowering. Do not be alarmed if the leaves fall off! That is natural for these deciduous orchids. Hobbyists living in sub-tropical South Florida often hang them outside under a tree and essentially, forget them until buds develop.
With more than a thousand species in the genus, there are many other fine dendrobiums for the hobby grower. Dendrobium kingianum is a delightful compact plant that is especially popular among northern growers because it does best with slightly cooler temperatures, especially in winter. Dendrobium lindleyi (also known as Dendrobium aggregatum) delights hobbyists with its chains of gold-coin flowers. Dendrobium anosmum produces raspberry-scented flowers along deciduous second-year canes and is a hit at spring orchid shows. While some dendrobiums can be quite large, there are also compact to miniature species for both warm and cool climates. Dendrobium unicum is a small adaptable species that is easy to grow if you have a bright window or greenhouse. Although somewhat challenging for the beginner, Den. delacourii prefers intermediate temperatures and has flowers with an interesting tasseled lip while Den. cuthbertsonii is a staple in cool greenhouses across the country. If you are really limited for space, the miniature Den. peguanum needs warm temperatures and a well-defined winter rest.
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| Den. lindleyi |
Den. anosmum |
Den. delacourii |
Den. cuthbertsonii |
If you are an AOS member, visit Orchids A to Z where you can go through the genus by section and see some of the marvelous species in this wonderful family of orchids!
Greg Allikas
July 2011
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