OrchidSafari ARCHIVES*: Dendrobiums and Conservation Challenges

OrchidSafari Conservation Series vol. 33
Topic: Dendrobiums and Conservation Challenges
Moderator: Marilyn H.S. Light
Wednesday, April 12, 2000

[Pre-chat material on culture follows the topic notes]

MarilyninOttawa
Hello everyone. Welcome to the discussion of the genus Dendrobium. This is a huge genus of perhaps more than 2000 species so I have limited myself to a few examples to represent the genus.

When I began growing orchids in 1970, I was living in Barbados, West Indies. My first orchid gift was a blooming plant of Den. superbiens (which we will see later). As I read the society library, I came to realize that I could probably grow many of the Australian Dendrobiums of North Queensland and Papua New Guinea. So, my first purchased orchids were hybrids bred in the vicinity of Cairns, Qld. I also purchased hybrid Dendrobes from Jones & Scully in Florida. Most of my chosen plants thrived!

What I did learn in those early days was that the tropics are not simply the tropics. There are regional differences such as precipitation patterns and altitude. Not all tropical orchids grew well in the humid tropics. Some liked it cooler or dryer for extended periods. It is with this wisdom that I approach the subject. After all, we are talking conservation and we want our precious plants to thrive!

The first plant I illustrate this evening is one discussed in the pre-chat, Den. alexandrae.

Den. alexandrae is an interesting example of what can go wrong when knowledge is lost. Rudolf Schlechter discovered this lovely orchid, collected herbarium specimens (which were later destroyed in WWII) and thankfully, published the description with drawings in his book Die Orchideen von Deutsch-Neu-Guinea, and Oakes Ames had photographed many of the type specimens before the war. Reference to these drawings was what we used to identify newly found specimens.

Susan-from-Oregon
Botanical illustrators save the day!

MarilyninOttawa
Den. alexandrae belongs to the Latouria section. These plants are easy to grow, this species being capable of producing numerous spectacular flowers in northern hemisphere winter. Flowers last 4 weeks. They are borne on 12 inch tall pseudobulbs. A close ally is Den spectabile.

CJ-Orchidflowerchild
And Den. macrophyllum. I think the Latourae Dens have the wierdest and most interesting flowers of all Dens.

MarilyninOttawa
The next species we will look at is Den. bracteosum which is a member of the Pedilonum section. This low altitude New Guinea species grows fast. Pot or mount seedlings in living moss.

The Den. bracteosum comes in a variety of colors ranging from pink through greenish white. The flowers are numerous and long lasting, at times completely covering the canes. This species can range from lower to higher altitudes. If a specimen does not thrive, try growing it a bit cooler.

John_in_Arcadia,_CA
What is the temperature range of this type of Dendrobium?

MarilyninOttawa
I know that many of you will ooh and aah over the next one, Den. cuthbertsonii.

Caroline,_Oregon
That's what I need to cheer me up!

pecteilis_in_KY
This is a cool grower, isn't it? Aren't there some that short that are warm growers?

John_in_Arcadia,_CA
That one has such a reputation for difficulty that I have never tried it as the plants are so expensive.

Fleur
Thats an unusual colour combination on the cuthbertsonii. Den cuthbertsonii is grown well here in Tasmania, I think the only area it hates is my greenhouse. Sigh

Ellensmithown
I always manage to bloom them and then they decline and die

MarilyninOttawa
Den. cuthbertsonii is a member of the Oxyglossum section. In 1912, Schlechter said that he soon hoped this species would be in cultivation. Oxyglossum Dendrobiums are some of the most spectacular as far as color is concerned. Den. cuthbertsonii grows quickly, flowering as little as 1.5 years out of flask. Never let the roots dry out!! Moss forest species have evolved to expect regular mists. clouds and showers of water. Use good quality water! Grow these plants if you can in living sphagnum at about 65F by day, 55F by night. Provide good air movement. The plant you see is part of one growing in about a 3 inch pot. It is very brightly colored.

Kathy_in_N_Calif
The color combination looks like that type of bicolor, which gets many awards around here, and can cost dearly.

MarilyninOttawa
Our next example is one of the section Formosae, formerly known as the Nigrohirsutae section because of the black hairs frequently found covering the pseudobulbs. Some of this section come from the Philippines, others from Thailand and Burma. All have spectacular flowers whether they are white as in Den. infundibulum or colored as in Den. cruentum. The pictured Den. infundibulum grows about 3 feet tall under 50% shade. It prefers coolish conditions but grows well under house conditions here in Canada. When I say house, I mean kitchen counter with bright sunlight streaming in from a nearby window! This species is a very important parent of many popular hybrids including (x formosum = Den. Formidible), (x cruentum = Den. Fire Coral).

Susan-from-Oregon
So showy! I'm surprized that this group isnt more popular. Is it hard to grow? Special requirements?

Fleur
It is a lovely thing isn't it. Almost like a catt.

Karen
The infundibulum looks like something a bride should carry in her bouquet.

MarilyninOttawa
The next species I chose is an Aussie, Den. kingianum, from Queensland.

Jose41822
The D. kingianum looks like the color's painted on the petals & sepals. Nice.

ClareinLA
They do real well outside here. Strong growers.

John_in_Arcadia,_CA
Yes, mine Clare has bout 50 spikes open now. That was the one you saw sitting on the lawn

Susan-from-Oregon
Mine has never bloomed. I'm taking it onto the lawn NOW!

MarilyninOttawa
Den. kingianum has been both line bred for better color, shape and size as well as hybridized with many other Aussie species to make some spectacular and floriferous hybrids. I have found that Den. kingianum responds very favorably to Jerry's Grow fertilizer. This season, my plant (pictured) produced twice as many flowers per stem and many more stems than usual. This orchid is quite fragrant especially in the morning. Grow this species warm with plenty of light and water in summer then let dry out when the canes have reached their full length. Flowers follow a few months later. This species matures its capsules within 60 days so anyone wanting to play the bee does not have long to wait for seed!

Fleur
Oh, it's got some lovely colouring. I'm glad I got to see it. This is a more "Normal" colouring of a kingianum. Not as bright as the one we just saw. picture

MarilyninOttawa
Our next species is a special favorite of mine although I cannot grow it here in Canada. Den. lasianthera or the May River Red, has been formerly known as Den. ostrinoglossum. I saw my first plant growing amongst a pile of stumps on a beach patio in Barbados, West Indies. The plant was about 6 feet tall and covered with blooms.

Kathy_in_N_Calif
Yes, the colors look like a carnival!

Fleur
Wow, that's some plant. I like that a lot.

MarilyninOttawa
The May River Red (Sepik Blue) grow in mangrove swamps of New Guinea. It is a member of the Spaulata (syn. Ceratobium) section or the Antelope section. This species must have heat and humidity to thrive. Den. canaliculatum is a miniature antelope type species which was used to make Den. Pixie Princess. The corkscrew 'ears' are a very dominant trait!

ClareinLA
Wow! Imagine having that 6 foot tall plant in the back yard!

MarilyninOttawa
I think you can see why I miss having my tropical garden!! To clarify matters, I grew many orchids in the West Indies but Dendrobiums originate in Australasia, not the New World!

For those of you who want something small, consider Dockrillia lichenastrum (syn. Den. lichenastrum). This creeping epiphyte of North Queensland, Australia, is best grown mounted in a humid environment. The temperature can drop to 45 F in winter. Den. lichenastrum is quite tiny, the picture was taken 1 to 1. Flowers are just about 1 cm wide.

Susan-from-Oregon
What a cutie! Love those leaves

Fleur
I haven't seen one of those before, just delightful. I have a few of the Dockrillia type Dendrobiums but not that one.

CJ-Orchidflowerchild
I have Dockrillia teretifolia. It is an interesting little plant with graceful flowers.

Earl_in_Vacaville,_CA
Used to be a very large specimen of this in Foster Botanical Garden in Honolulu. Loved it!

Zeynep
Marilyn I like it :-)

MarilyninOttawa
Our next specimen is a hybrid, Den. Merle Sado. This is a typical phalaenopsis-type Dendrobium. There are two species intermingled in this type of breeding, Den. biggibum and Den. phalaenopsis. When I first started growing Dendrobes, I was obtaining hybrrids made with Den. phalaenopsis var. compactum. This is now known as Den. lithocola. This type is is found growing in a very limited area just north of Cairns in N. Queensland. As you can imagine, the parentage of our phalaenopsis-type Dendrobiums is somewhat confused. But it does matter which parents were used as far as the response of progeny to culture is concerned. Den. Merle Sado has inherited some of the better traits of this group. Not only are the flowers nicely shaped but the plant is not fussy. Some of this type are quite fussy, dropping buds if there is a rapid change in humidity, or if you move the plants, or whatever. Those having the compact form (Den. lithocola) in the parentage may tend to produce keikis rather than spikes when stressed. It pays to keep track of the parentage.

Jose41822
Where do you get those plants? The colors are spectacular.

MarilyninOttawa
Our next example is Den. pulchellum. The species is from Burma/India and comes in two color forms. What you see is the coloured form: another has no 'eyes' , that is, no color blotches. This plant grows to about 3 feet tall and about as wide. It blooms in spring after which growth resumes. Grow this plant warm with plenty of moisture and fertilizer to obtain the biggest canes possible. Once growth is finished, dry the plant out but keep well illuminated.

CJ-Orchidflowerchild
What are the cultural requirements of pulchellum?

MarilyninOttawa
Den. pulchellum belongs to a group of Dendrobiums which can be very challenging to flower although most will grow well under a variety of conditions. For those of you in warmer areas, I recommend trying Den. anosmum (raspberry scent and magnifecent blooms) and Den. loddigesii (masses of pink and yellow blooms).

Karen
Oooh, raspberry scent! Sounds yummy.

CJ-Orchidflowerchild
It is.

BobMonkey
Does the pulchelllum have a strong scent? I have a similar looking orchid growing in one of my coconuts.

MarilyninOttawa
Den. pulchellum is not particularly scented.

Bobmonkey
I have a den. anosmum in bloom now that is great, it's inside the house and the scent is almost overpowering. It's a hybred from Kauai with fat canes. Will post a picture on my web site when I unload my scanner.

Susan-from-Oregon
I look forward to seeing it.

MarilyninOttawa
Our next example is Den. senile.

Karen
Senile-as in 'senior moment'? Very pretty yellow.

Susan-from-Oregon
Very attractive. Is it as compact as it looks? Senile is also a botanical term refering (I think) to white hairs.

MarilyninOttawa
There was a good article about Den. senile published in the AOS Bulletin Vol 56, November 1987. This is a small hairy plant with beautiful yellow blooms. I am certain that many wild-collected plants have perished during vain attempts to establish them but hopefully illicit trade is now ended. Wild-collected specimens are very challenging to establish although the plants will bloom in desperation! Grow this species mounted, provide good air movement and a substantial drop in temperature between day and night. It can survive warm days if nights are cool. You can also try growing it in a clay pot since evaporative cooling from the clay surface should help matters.

MarilyninOttawa
Den. senile is so named because of its hairiness, all over. The hairs are soft but the flowers are quite substantial. The picture was taken at 1 to 3.2 magnification.

MarilyninOttawa
Our next example is yet another Aussie, Den. speciosum or the Rock Lily. This species is really a complex of several species ranging along the east coast of Australia. There are pure white-flowered kinds and yelow-flowered sorts and a range in between. As Allison and Mark Webb wrote in their article in the Bulletin, July 1994, "Returning the plants to the wild where they did not originate has further complicated matters......"I throw this in as an advisory to those of us in a hurry to re-introduce species. Know the provenance of your material.

ClareinLA
I'll definately make room for that one!

Zeynep
That is a nice flowers, just like mine... that is the size of the plant, meaning the height?

MarilyninOttawa
Den. speciosum is a massive plant. The picture is of one at the WOC show in New Zealand where there were many on show. If I grew it, I would do so as with Den. kingianum. Lots of light, warmth and water in summer followed by a dry rest for a few months.

MarilyninOttawa
Den. stratiotes is another plant that I want to show to you. This one is growing in a tub of broken bricks in full sun in Barbados. This species comes from Sulawesi (Celebes) and Moluccas islands north of Australia. It requires perfect drainage. Even in nature, its roots perch above the substrate. This makes a lovely specimen measuring about 2.5 to 3 feet tall.

ClareinLA
A nice plant for those granite rocks you were talking about a few sessions ago, I think.

MarilyninOttawa
Den. stratiotes is a famous parent of modern warm-growing dendrobes. Crossed with Den. phalaenopsis, we get Den. Caesar, a parent found in many semi-antelope dendrobiums today.

MarilyninOttawa
My last example is Den. X superbiens which is believed to be a natural hybrid between Den. bigibbum and Den. discolor (syn. undulatum). The latter species grows to 6 feet close to the ocean in North Queensland and Papua New Guinea. The antelope-horned flowers are yellow to golden brown and last weeks on end. The Den. bigibbum is a modest, lavender pink-flowered plant. Together we get a vibrant red purple semi-antelope bloom. This was my first orchid folks and I proudly took these flowers to the 8th WOC in Frankfurt, Germany.

ClareinLA
You never forget your first, do you.

MarilyninOttawa
I want to thank Kathy for helping with the pics. Now that the pics are done, I open up the forum to discussion.

CJ-Orchidflowerchild
What about D. d'albertisii? Any cultural tips, Marilyn? Mine is growing like gangbusters in my room. Now, if the dad-burned thing would just bloom!

MarilyninOttawa
CJ. Den. d'albertisii is a synonym for what is now called Den. antennatum. It is closely allied to Den. stratiotes. Both do not like to have their roots in medium. Use very coarse potting medium keeping the plants perched above the medium so they have a choice as to where to put their roots. Provide lots of light and good air movement. Warmth too! These plants can grow very quickly out of flask and will be almost never out of bloom. Some clones self pollinate.

janetteh
We have Den. stratiotes growing in lava rock and it really seems to like it.

Kathy_in_N_Calif
Would Den. d'albertisii be better on a plaque?

CJ-Orchidflowerchild
Thank you, thank you very much, Marilyn!

Kathy_in_N_Calif
Susan had a question about the negrohirsuite dens, any cultural info? dry rest? etc?

MarilyninOttawa
The Formosae (Nigrohirsutae) are quite variable as to their requirements. Some come from hot lowlands, others from cool uplands. It depends which you have. Hybrids of this group are most forgiving.

Kathy_in_N_Calif
Most of mine are of the Dawn Maree strain.

Susan-from-Oregon
I don't see them around much. So showy. I wonder why they're not more popular?

MarilyninOttawa
Next month, my topic will be another big group, Epidendrum and Encyclia. This is a New World group and a wide-ranging one with plenty of scope for discussion. See you there! All pictures shown this session are Copyright Michael MacConaill please. Michael is my husband. He also was honored that the AOS featured one of his pics in the AOS photographer Hall of Fame on their web site. I give him a big hug for all his help.

Kathy_in_N_Calif
Marilyn, before you go.... What is the common characteristic which makes alll these weirdly different orchids Dendrobiums???? Taxonomists will split and split paphs, yet leave Dens alone....

MarilyninOttawa
Regarding what makes Dendrobes, Dendrobiums, they are characterized (according to Dressler) by naked pollinia without caudicles, by a prominent column foot and by a particular seed type. Also, the root covering (velamen) is of a particular type. I think that the flower structure namely the clumn foot is the most recognizable by us.

Kathy_in_N_Calif
Night Marilyn

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Pre Chat Handout:

The genus Dendrobium is a very large one with over 2000 species ranging through many Australasian countries including Australia, the Philippines, Papua-New Guinea, Thailand, Burma, India, and China. The genus is divided into sections such as the Latouria Section, comprising allied species such as Den. alexandrae, atroviolaceum, and finisterrae. Some groups of species have been established as new genera as with the genus Dockrillia which comprises the terete-leaved sorts including D. lichenastrum, D. cucumerina (syn. Den. cucumerinum) and D. rigida (syn Den. rigidum). There is, however, the challenge of how to name hybrids made between Dendrobium and new genus constructs. Following standard policy, the International Orchid Registrar has chosen to do what has already been done with that other large genus Epidendrum. The Registrar will not apply any major taxonomic decisions until they have been widely accepted in the scientific and horticultural communities, and the majority of plants in collections and nursery stock have been re-labelled.

Dendrobiums are subject to a wide range of conservation challenges ranging from illegal collection through to raising healthy, flowering plants in collections. Unforseen and catastrophic events can have an impact elsewhere. In the early 1900's, Rudolf Schlechter explored parts of what is now called Papua New Guinea. He discovered many orchids including one he named after his wife, Alexandra, Dendrobium alexandrae. His herbarium specimens were destroyed during the bombing of Berlin in World War II. Thus, workers had to rely on existing drawings to confirm that what they had recently rediscovered was indeed the beautiful Den. alexandrae.

Conservation of Plants from Wild-Collection
Only a few years ago, it was common to see piles of leafless, rootless Dendrobiums for sale at shows. Thousands of plants of species such as Den. bellatulum, cruentum, senile and oligophyllum were gathered and sold to curious buyers often with little skill to restore these plants to vigorous growth. One species, Den. cruentum, was so threatened that it was proposed for protection under CITES Appendix I.

Ex-situ Conservation
Richard Warren of Equatorial Plants has done much to promote the raising of especially the New Guinea Dendrobiums from seed. His series of articles in the AOS Bulletin (Orchids) on the New Guinea species was exemplary. He points out that most Latourea Section species are easily raised ex flask. He cautions to never let the roots of Den. cuthbertsonii and relatives dry out. Equatorial Plants offers seedlings of many rare and unusual species including those of Den. alexandrae.

Raising Healthy Plants to Blooming Size
Raising Dendrobiums, especially species uncommon to cultivation, requires some knowledge of the habitat where the seed parent originated as well as a good measure of sign language interpretation, that is, knowing what the plant is telling you. Dendrobiums can come from hot, steamy lowlands, from seasonally dry rock faces, from medium- and high altitudes, from cloud forest, and from monsoon regions. Plants which normally experience an extended dry, cold rest period will not flourish if grown warm and wet year round. Likewise, plants which come from hot, humid mangrove swamps will suffer if raised in a dry, cold apartment window.

SIGN LANGUAGE OF CANE-TYPE DENDROBIUMS such as Den. phalaenopsis, nobile, finisterrae, kingianum and pulchellum.

I WANT TO GROW - NOW!! = A new shoot appears followed by root nubs.

Response: Keep the temperature regime as is for the plant has responded to this. Ensure that the potting medium is fresh and if not, repot. Always under pot and use coarse medium. Alternatively, mount the plant. Water well and frequently. Fertilize once roots begin to penetrate new medium. Provide enough light to encourage sturdy growth.

I WANT TO STOP GROWING - NOW!! = The shoot develops a small terminal leaf. The pseudobulb begins to swell.

Response: Stop applying fertilizer. Gradually discontinue watering. Nights can be cooler once roots are dry. Maintain moderate to high light, moderate humidity and good air movement. Do not resume watering or misting until the I Want To Grow sign happens.

YOU WATERED ME OR KEPT ME TOO WARM WHEN I WAS RESTING !! = A small plantlet (keiki) appears where you were expecting flower buds.

Response: Don't panic! Consider this message both as a warning and a bonus. After all, you now have a keiki or two to share with friends. You will probably find that the plant is also ready to start growing again. Follow the instructions covered in I Want to Grow. When the plant signals that it wants to stop growing, respond appropriately. This time, try to keep the plant resting as long as possible or about 2 to 4 months. Watch for the I Want To Bloom sign.

I WANT TO BLOOM!! = Swellings appear at nodes along the pseudobulb, opposite to or in the axils of leaves or where leaves have since fallen, or at the tip of the pseudobulb.

Response: Get excited but resolve to keep the plant in the same position until the buds open. Dendrobiums can be very fussy about their conditions and drop buds without warning. If you must move the pot, mark the pot so that you will return it to the exact position relative to the direction of light. Mist the plant but avoid watering until new roots appear. Keep the temperature regime as is.

SIGN LANGUAGE OF DENDROBIUMS OF THE MOSS FOREST

ARGHHH!! = You kept me to dry and now its too late!

Dendrobiums of the moss forest such as Den. cuthbertsonii, dichaeoides, and pseudoglomeratum, live a life in perpetual moisture whether it is rain or mist or cloud. In fact, if you can raise nice, healthy moss, this is the best sign that you have the conditions to raise moss forest Dendrobiums. The moss will tell you if you have salts build up (moss turns pale or reddish) or if it is too dry (moss shrivels). What is good about this is that the moss will signal before conditions are endangering the orchid.

Plant seedlings in living moss established on a mount or in a small pot.. Provide the same light, good air movement and copious good quality water that established the moss.

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