Tuesday, 22 September 2015 19:56

How We Grow Dendrobiums - R.F. Orchids

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Dendrobiums are native to a huge area in Asia, ranging from southern Japan and the eastern foothills of the Himalaya south into India, the Indo-China peninsula, Malaysia, Indonesia, New Guinea and Australia. In this large range, there are at least 1,000 species, inhabiting virtually every tropical and subtropical habitat, so it is impossible to generalize about their cultural requirements. Some live in areas that are warm all year long, some grow in cool cloud-forests. Some thrive in conditions that are generally moist all or most of the year, some are adapted to sharply seasonal wet/dry cycles. We grow many dendrobiums from the warm to intermediate temperature habitats, and we’ll share our experience with some of these extraordinarily beautiful orchids.

 

Dendrobiums are native to a huge area in Asia, ranging from southern Japan and the eastern foothills of the Himalaya south into India, the Indo-China peninsula, Malaysia, Indonesia, New Guinea and Australia. In this large range, there are at least 1,000 species, inhabiting virtually every tropical and subtropical habitat, so it is impossible to generalize about their cultural requirements. Some live in areas that are warm all year long, some grow in cool cloud-forests. Some thrive in conditions that are generally moist all or most of the year, some are adapted to sharply seasonal wet/dry cycles. We grow many dendrobiums from the warm to intermediate temperature habitats, and we’ll share our experience with some of these extraordinarily beautiful orchids.

 

Botanists place groups of related species into “sections”, to help organize and identify plants. Here in “part 1”, we’ll discuss some of the related species from Section Dendrobium. These are sometimes referred to as the pendent, and/or deciduous dendrobiums, as most of them produce pendent stems (or “canes”) that are often leafless during their dry-season resting period. There are estimated to be 50 to 60 species in this group.  Of those, we grow about a dozen species: Den. anosmum (superbum), Den. aphyllum (pierardii), Den. parishii, Den. nobile Den. signatum, Den. albosanguineum, Den. moschatum, Den. fimbriatum, Den. primulinum, Den. pulchellum, Den. senile, Den. unicum.

 

Most of these species are native to northeastern India, and parts of the Indo-Chinese peninsula, although one species, Den. anosmum (also known as Den. superbum) is common from the Philippines through Malaysia and Indonesia. This group of dendrobiums is popular for the spectacular, fragrant show of flowers in the springtime.

 

Cultural requirements

Fortunately, the most popular species in the group all have similar cultural requirements. They grow robustly during spring and summer; growth stops altogether in late fall, and the plants may drop their leaves during the winter resting period.

 

Temperature. In their native habitat, these orchids experience mild to warm daytime temperatures in spring and summer, and generally cooler temperatures in the winter. For most, the winter night temperatures range from about 45°F to about 55°F. Den. superbum, particularly the plants from the Philippines, prefers winter nights about 10 degrees warmer than that. These plants do well for us with our normal winter night temperatures, which are usually in that range.

 

Light. While actively growing, give the plants plenty of bright but filtered light. They will grow well under the same light conditions as most cattleyas. Most of these dendrobiums grow attached to deciduous trees, so they want higher light in winter. We grow them under cattleya light levels during the growing season, and move them to vanda light levels during their resting period.

 

Water.This may be the most crucial element to success with these orchids. Their native conditions are fairly wet during the late spring, summer and early fall. Rainfall is quite heavy for a few months, but it tapers off in the late fall, and winter months are fairly dry. Water the plants regularly when they are actively growing. Mounted plants can be watered daily if air circulation is good.

 

Observe the tips of the canes; in the fall, they will stop producing new leaves. This is the signal that the plant has finished growing for the season; gradually reduce watering, and allow the plant to dry somewhat between waterings. There’s some moisture in the habitat at this time, so the plants do get a little water from dew or fog; a light watering every few days is all they need. Growth will start again in the late winter or early spring at about the same time that the flower buds begin to form; once the buds have formed, and new growth appears, increase watering again.

 

Remember, it’s quite typical for these dendrobiums to drop all or most of their leaves during their winter resting period. Flower buds will appear on the stem opposite the attachment points of the leaves, and new growth will commence from the base of the previous year’s growth.

 

Fertilizer. These dendrobiums benefit from regular feeding when they’re actively growing. Any balanced, water-soluble fertilizer can be used, diluted according to package directions. Jack’s Classic 20-20-20 is a good option; we feed once a week during the growing season. Reduce feeding in the fall and eliminate it completely when the plants are resting in the winter. Resume feeding after the flowers have finished.

 

Potting. The pendent stems of these orchids make them a challenge to grow in pots, so they are usually grown mounted, or in hanging baskets. The larger species can grow to great size, so if mounted, the mount material should be sturdy – a cork slab or dense tree fern plaque works well. Mounted plants can be watered daily in summer if the air circulation is good. In a basket, use a very well-drained epiphyte mix. We prefer to mount these dendrobiums.

 

Problems. These dendrobiums have few really major pest problems. Snails and slugs may damage the leaves and canes, and occasionally during wet weather you may see some minor damage from leaf-spotting fungal diseases.

 

If, in the spring, the plants produce keikis (baby plants) on the stem instead of flowers, the plant is telling you that something in its environment is not correct. This may be too much water during resting; the plants need a little watering during this time but they must dry completely for two or three days between waterings. It may also be a temperature problem…these dendrobiums want mild to warm days in winter, but much cooler nights. And they need higher light in the winter, too.

 

Section 2

 

In this “chapter” on growing dendrobiums, we’ll cover the species in Section Callista. These are spring-blooming orchids native to mainland Asia, most commonly northeast India, northern Thailand and adjacent areas. Although the flowers typically last only about a week, they are among the most spectacular orchid displays you’ll ever see. Botanists include about 10 species in this section, and we grow most of them.

 

Cultural requirements

Fortunately, the most popular species in the group all have broadly similar cultural requirements. They grow robustly during spring and summer; growth stops altogether in late fall, but the plants do not drop their leaves during the winter resting period. Most of these orchids have upright pseudobulbs with a cluster of a few leaves at the top. The stems are usually spindle-shaped. Den. farmeri’s stems are 4-angled, Den. chrysotoxum’s are swollen and ridged. In the spring, the inflorescence develops from a node on the stem just below the leaves. Den. lindleyi and Den. jenkinsii have shorter, more flattened pseudobulbs and typically only one, or at most two, leaves per pseudobulb.

 

Temperature. In their native habitat, these orchids experience mild to warm daytime temperatures in spring and summer, and generally cooler temperatures in the winter. For most, the winter night temperatures range from about 45°F to about 55°F. Like the species in Section Dendrobium (described in “Part 1”),  these dendrobiums do well for us with our normal winter night temperatures, which are usually in that range. Den. chrysotoxum does best on the warmer end of that range, while Den. densiflorum, Den. lindleyi (aggregatum), Den. jenkinsii and Den. thyrsiflorum prefer the cooler end of it. 

 

Light. While actively growing, give the plants plenty of bright but filtered light. Most will grow well under the same light conditions as most cattleyas. Many of these dendrobiums grow attached to deciduous trees in their native habitat, so they want higher light in winter. Den. chrysotoxum and Den. lindleyi need more light; provide as much light as possible without burning the leaves.  We grow these two under near-vanda light levels. It is normal for the pseudobulbs of Den. chrysotoxum to be more yellow than green.

 

Water. As with the species in Part 1, watering may be the most crucial element to success with these orchids. Their native conditions are fairly wet during the late spring, summer and early fall. Rainfall can be quite heavy for a few months, but it tapers off in the late fall, and winter months are fairly dry. Water the plants regularly when they are actively growing; mounted plants can be watered daily if air circulation is good. When the new pseudobulbs have matured in the fall, gradually reduce watering, and allow the plant to dry between waterings. There’s some moisture in the habitat at this time, so the plants do get a little water from dew or fog; a light watering every few days is all they need. It is normal for the pseudobulbs to shrivel somewhat during the resting period, but don’t allow the plant to dehydrate completely! During the coolest periods in winter, keep the plants fairly dry.

 

Fertilizer. These dendrobiums benefit from regular feeding when they’re actively growing. Any balanced, water-soluble fertilizer can be used, diluted according to package directions. Jack’s Classic 20-20-20 is a good option; we feed once a week during the growing season. Reduce feeding in the fall and eliminate it completely when the plants are resting in the winter. Resume feeding when the plant begins to grow again.

 

Potting. Because most species in this this group have upright pseudobulbs, the plants can be grown in pots or baskets, or mounted on a sturdy substrate like driftwood or teak root. Mounted plants can be watered daily in summer if the air circulation is good. In a pot or basket, use a very well-drained epiphyte mix; we prefer an inorganic product like expanded clay, as these orchids do best when their roots are undisturbed. We usually grow them in baskets, or on mounts. Den. jenkinsii and Den. lindleyi (aggregatum) do best mounted.

 

Problems. These dendrobiums have few really major pest problems. Snails and slugs may damage the leaves and canes, and occasionally during wet weather you may see some minor damage from leaf-spotting fungal diseases. Scale insects can be a problem, particularly on plants of Den. lindleyi (aggregatum) and Den. jenkinsii.  Mites are a possible problem on the softer-leafed species such as Den. farmeri. Stale or decayed potting medium can lead to root problems, as with any potted orchids.

 

If a mature plant doesn’t bloom in the spring, something in its environment is not correct. This may be too much water during resting; the plants need a little watering during this time but they must dry completely for two or three days between waterings. It may also be a temperature problem…these dendrobiums want mild to warm days in winter, but much cooler nights. And they need higher light in the winter, too.

 

Section 3

 

In this “chapter” on growing dendrobiums, we’ll cover the plants in two closely-related sections: Phalaenanthe and Spatulata, commonly known as the “phalaenopsis type” and “antelope type”. The species interbreed readily and most of the popular dendrobium hybrids, sometimes called “den-phals”, are descended from these two groups. The “phalaenopsis” or “den-phal” type gets its name from the flowers’ resemblance to Phalaenopsis orchids; the plants produce arching sprays of flat, white or pink to red-purple flowers. 

 

The “antelopes” typically have twisted sepals and upright, twisted petals that suggest an antelope’s horns, and have a wider color range.  Some hybrids between the two groups, especially those with a lot of “antelope” ancestry, are called “semi-phal”, as the flower characteristics are intermediate between the two.

 

These orchids are native to northern Australia, parts of New Guinea and Irian Jaya, where they inhabit two different climate areas. The species native to Australia generally experience a very seasonal climate, with distinct wet and dry periods during the year; the New Guinea species hail from areas where there is moderate to heavy rainfall throughout the year, with little if any dry season. Understanding this difference is important to success with these dendrobiums, particularly as the most popular “den-phal” hybrids have the most seasonal species in their ancestry.

 

Cultural requirements

Except for the seasonal rainfall pattern in their habitats, other growing conditions are similar. These are generally upright plants, with leafy, tall, cylindrical pseudobulbs or “canes” that can grow to quite large size in some of the New Guinea species. Den. canaliculatum and Den. affine, from Australia, are typically compact growers and their relatively small size is often used to reduce the plant size in hybrids, but some of their cousins can produce canes 6 or more feet tall.  Even the common “den-phals” one sees in nurseries and garden centers are often two or three feet tall; a well-grown plant of Den. violaceoflavens can reach 7 feet or more in height, without the long stem of flowers. Not many “windowsill” orchids among the species in these sections!

 

Temperature. All of the species in these two groups, and consequently their hybrids, are very warm-growing. Only Den. crispilinguum will grow under “intermediate” conditions, with night temperatures below about 60F; it grows at higher elevations in New Guinea, and is not common in cultivation. The rest require warm to even hot daytime temperatures, and warm (above 60F) nights, year-round. Exposure to cooler temperatures can result in rapid leaf-drop, so these dendrobiums need to be protected in cool weather. Even here in South Florida, our winter nights can be too cool for these orchids to remain outdoors.

 

Light. These are generally high-light orchids. Some of the species grow in full sun, and all want as much light as possible without burning the leaves. Most will do well under “vanda” light conditions.

 

Water. As indicated earlier, these orchids fall into two groups with respect to watering. The Australian species are native to areas with a distinct dry season. This group includes Den. bigibbum, Den. phalaenopsis, Den. affine (syn. dicuphum), Den. canaliculatum and Den. undulatum (syn. discolor).  During the summer and early fall growing season, water generously and regularly, but gradually reduce water in the fall and keep the plants on the dry side through the winter and early spring. Humidity is fairly high during the dry season, so the plants do need a little water, but allow them to dry thoroughly between occasional light waterings. Most of the common “den-phal” hybrids are in this group.

 

The second group, which includes the New Guinea “antelopes”, come from habitats where rainfall is moderate to heavy all year, with only a slight reduction (if any) in moisture for a short period in late summer or early fall. These plants do not want a dry rest. Water regularly throughout the year, and make sure the potting medium drains well. Good air circulation is important. Species in this group include Den. antennatum, Den. gouldii, Den. lasianthera, Den. lineale, Den. mirbelianum, Den. stratiotes, Den. strebloceras, Den. sylvanum, Den. tangerinum and Den. violaceoflavens. Hybrids with mostly “antelope” ancestry require these same conditions.

 

In all cases, be careful with water when the new growths begin, and keep water out of the tops of the new growths until they are two or three inches tall. The new growth is highly susceptible to rot if water is allowed to collect in the tip.

 

Fertilizer. These dendrobiums benefit from regular feeding when they’re actively growing. Any balanced, water-soluble fertilizer can be used, diluted according to package directions. Jack’s Classic 20-20-20 is a good option; we feed once a week during the growing season. For the dry-season plants, reduce feeding in the fall and eliminate it completely when the plants are resting in the winter. Resume feeding when the plant begins to grow again

 

Potting. Given the size of most of these orchids, pots are the best solution, and heavy clay pots are a necessity. Like many other dendrobiums, these have fine root systems and do best when somewhat underpotted, with their roots crowded in a container that seems too small for the size of the plant. To add weight to an obviously top-heavy plant, set the pot into a larger size and fill the space between pots with clean river gravel for weight. The potting medium must be open, well-aerated and very free-draining; we prefer coarse expanded clay and/or coarse charcoal. Some successful growers use charcoal exclusively. Until the plant is well-established in its container, you may have to stake the tall canes to keep everything upright.

 

Problems. These dendrobiums have few really major pest problems. Snails and slugs may damage the leaves and canes, and occasionally during wet weather you may see some minor damage from leaf-spotting fungal diseases. In dry weather, mites can set up housekeeping on the underside of the leaves. Stale or decayed potting medium can lead to root problems, as with any potted orchids.

 

Reminder: all the orchids in these sections are very warm-growing. The plants must never be exposed to cool temperatures.

 

With good care, these orchids are capable of blooming multiple times from the same canes!

 

Section 4

 

Another group of Dendrobiums, section Pedilonum, includes about 80 species from a wide swath of Asia, from India across southeast Asia to the Philippines and south to New Guinea. Many of the species in this section are cloud forest plants which require cooler conditions than we have in South Florida, but some of the most beautiful and interesting species are warm to warm-intermediate growers, and we do cultivate those here at R.F. Orchids.

 

These orchids grow at sea level, or at low elevations, where the temperature is warm to hot all year long, and with two exceptions (noted below), the plants do not experience any significant dry season. We’ll cover Den. bullenianum (syn. topaziacum), Den. capituliflorum, Den. goldschmidtianum (syn. miyakei), Den. purpureum, Den. secundum and Den. smillieae. In this group, the individual flowers are small but the plants produce clusters of them all at once, making a spectacular display. Den. secundum and Den. smillieae are usually spring bloomers; the other species can bloom at nearly any time of the year.

 

 

Cultural requirements

For the most part, the warm-growing species in section Pedilonum are medium sized to large epiphytes, with slim, leafy canes (stems) that become pendent as they grow. Typically these canes are deciduous after about a year, and the plants bloom from nodes along the bare stems. Den. purpureum is the largest of the species in this group, with canes that can grow to three or four feet long; the plants strongly resemble Den. anosmum (superbum) but have different cultural requirements. There are several color forms of Den. purpureum; the most commonly cultivated forms are pink, and white with green tips.

 

Temperature. These dendrobium species require warm to even hot daytime temperatures, and warm (above 60F) nights, year-round. Exposure to cooler temperatures can result in rapid leaf-drop, so these plants must be protected in cool weather. Even here in South Florida, our winter nights can be too cool for these orchids to remain outdoors on cold nights.

 

Light. Grow these dendrobiums in bright shade, about the same light levels you have for your cattleyas. Den. smillieae will take somewhat brighter light during the winter months.

 

Water. In general, the species in this group come from habitats where there is year-round moisture. Most don’t need a dry resting period in the winter, although both Den. secundum and Den. smillieae should be watered less during the winter. Never allow the plants to remain dry for an extended period, however; in their native habitats rainfall is only slightly less in winter and early spring than in the rest of the year. Good air circulation is important, and the plants should be watered regularly but not be constantly wet.In all cases, be careful with water when the new growths begin, and keep water out of the tops of the new growths until they are two or three inches tall. The new growth is highly susceptible to rot if water is allowed to collect in the tip.

 

Fertilizer. These dendrobiums benefit from regular feeding when they’re actively growing. Any balanced, water-soluble fertilizer can be used, diluted according to package directions. Jack’s Classic 20-20-20 is a good option; we feed once a week during the growing season (spring through fall). If the plants are growing – making new leaves at the tips of the canes, or new growths from the base of the mature canes – fertilize regularly. During the shorter, cooler days in winter, feed less often.

 

Potting. These dendrobiums can be grown in pots, baskets or on mounts. Because most of them are medium to large plants with eventually pendent stems, many growers prefer to mount the plants on a sturdy substrate; cork, treefern, teak root or driftwood work well. It’s also possible to encourage upright growth by staking the new canes as they grow; left to themselves the canes will eventually become horizontal or pendent. Den. capituliflorum has shorter, thicker pseudobulbs that generally don’t require staking. The short form of Den. smillieae grows more upright than the large form. Plants in pots or baskets need an open, fast-draining medium.

 

Problems. These dendrobiums have few really major pest problems. Snails and slugs may damage the leaves and canes, and occasionally during wet weather you may see some minor damage from leaf-spotting fungal diseases. In dry weather, mites can set up housekeeping on the underside of the leaves. Stale or decayed potting medium can lead to root problems, as with any potted orchids.

 

Reminder: all the orchids noted in this chapter are very warm-growing. The plants must never be exposed to cool temperatures. (There are other species in Section Pedilonum which are cool or cool-intermediate growers; we don’t grow or sell those plants)

 

© 2012 R.F. Orchids, Inc. All rights reserved. Available here for educational and Informational purposes only.

http://rforchids.com/how-we-grow-dendrobiums-part-1/

http://rforchids.com/how-we-grow-dendrobiums-part-2/

http://rforchids.com/how-we-grow-dendrobiums-part-3/

http://rforchids.com/how-we-grow-dendrobiums-part-4/

 

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