Dendrobium culture: No, its not dead.

For most orchid growers nowadays, Phalaenopsis are the gateway drug to bigger and more expensive plants.  But the Phalaenopsis that are now widely available are the product of many decades of hybridizing toward producing a plant that will survive in the average home even when (shudder of horror), watered with ice cubes.   Orchids species are an entirely different beast.  With 30,000 species (at least) species orchids show growing patterns and seasonal cycles very different from your average hardware store Phalaenopsis.   That is why it is important to read about the plants you buy.  A lot of orchid growers do impulse buying and then are bewildered by the way their plants react. 

 An example of a plant that can confuse a novice grower that is trying species is Dendrobium devonianum.  It produces slim canes that can be almost a meter long.  Unlike the leaves of Phalaenopsis, the leaves of Den. devonianum are slim, delicate and are soon deciduous.   During the growing season a cane of this species has leaves near the growing end of the cane with the rest quite bare.   When the cane stops growing, it eventually sheds all its leaves and for months afterwards it looks like its dead.    If the canes have been exposed to strong light and have developed a purplish color, they can look even worse.

This is an adaptation to the cold dry season when the trees lose their leaves and it rains little.  The orchids then have to endure months of drought and harsh sunlight.   My plant blooms in April, just before the local rainy season starts.  For months it looks like a mass of dead and shriveled stems.   But this is deceptive.  In the nodes of those leafless stems the flower buds are maturing.  A well flowered plant is quite impressive.

If you look at the top photo, the orchid looks like its in a wretched condition, ready to be thrown into the trash can.   But if you look closely, you can see the remains of many inflorescences in the second longest cane.   Note the very small root ball.  That is not unusual, if a plant is well fed and watered it will produce just the minimum of roots it needs to fill its needs.   In the bottom photo you can see the cane covered with flowers.

Dendrobium (farmeri x densiflorum)

Sadly I lost this beautiful and floriferous plant.  But if I ever see this cross again for sale, I will buy it in a second!!

Sobralia callosa keeps getting bigger and better

I have this plant so that as I pass the shadehouse in the morning, when I leave for work, I can see if it has flowers.  The flowers last a single day, but the plant blooms several times a year.  The plant is very pot bound in a 3 inch pot, and yet it keeps producing new stems.  I plan to repot it soon.  This blooming is the biggest up to date.  The plant has proven to be asy to cultivate under my climatic conditions and impervious to local insect pest.  Unfortunately the flowers are delicate and are often damaged by insects or local birds looking for nectar.

Grammatoheadia Boynton Leopard, with most of its flowers opened.

Most of the flowers of the inflorescence of my plant of Grammatoheadia Boynton Leopard are now opened.  Although initially the inflorescence had about seventy five buds, it started dropping a number of them at the tip after most of the flowers were open.  I don't now if this is a natural occurrence or because I moved the plant from its original location to a place next to the house. and hanged it in a shady spot.

I was surprised that the flowers all turned toward the direction of the strongest light.  That means that on one side of the inflorescence you are looking at the flowers front and on the other you are looking mostly at their backs.  This inflorescence has a number of flowers that surpasses the inflorescences of all my other Grammatophyllum, except the massive inflorescence of Gramm. speciosum.  However this plant is positively tiny compared with an adult speciosum.

Bulbophyllum lobbii var, Malacca, blooming with multiple flowers for the second time in 2014

In the past I had tried to grow this orchid without sucess.  In January of 2013, I received this plant and the nominate variety.  Both were treated identically, potted in the same media and in the same type of basket, they were growing side by side.  The nominate type died a low and messy death, the var. Malacca has thrived and blooms very well.  I wonder what is the difference that caused the different outcomes in the cultivation of plants that are essentially identical in their needs.

Dendrobium Love Memory 'Fizz'

This Dendrobium nobile hybrid grew very well in the coastal lowlands of Puerto Rico.   Unfortuantely when the blooming season arrived it was the only adult nobile hybrid not to produce flowers.  Because it appeared that it would not bloom in the coast I took it to the mountains, to an elevation of 1000 feet over sea level.  Because the night temperatures are lower in the mountains than it the coast it appears this provided the needed stimulus to make the plant bloom and in a few weeks flower buds started to develop.  The flowers are holding up well even with the daily downpours that tend to damage less sturdy ones.

Dendrobium farmeri, a significant blooming six months after its blooming season.

My plants of Dendrobium farmeri blooming season is in March and April.   Their blooming pattern is fairly predictable, the plants produce a number of inflorescences in March, and then about a month later, they produce a second blooming.   Not all plants bloom that way, in my area Dendrobium farmeri albiflorum produces a single flush of inflorescences and that’s it for the year. 

Sometimes the plants that produce pink tinged flowers produce single inflorescences long after the blooming season has passed.  These inflorescences are produced erratically and don’t seem to conform to any blooming schedule.  But in 2013 my largest plant produced four inflorescences in September, the largest blooming event ever outside its normal blooming season.  This is not the only plant to bloom six months after its normal blooming season, a large Coelogyne parishii also produced a few inflorescences in September.  

What really sets these blooming events apart from the ones that occur in Spring is the fact that all the inflorescences came from latent buds low on the stems of older pseudobulbs.  In the normal blooming season the inflorescences come from the highest bud in the previous year growths.  This means the inflorescence is produced just under the leaves of the stem.  The autumn inflorescences in my plants were all produced from buds halfway down on the stems of old pseudobulbs.

Domingoa haematochila (Rchb. f.) Carabia 1943, in situ in Mona Island in the Caribbean

This flower opened in the morning after a spell of strong rain

A whole plant view.  This plant had five inflorecenses, two with flowers.

For many years, in the eighties and nineties, I used to visit Mona Island on a yearly basis.   One of the things that lured me to Mona was that it is full of many interesting species of plants and animals.   I was particularly intrigued by the orchids of Mona.  The environment of Mona Island is not one that most people would associate with orchids. 

Most of the island is a plateau composed of limestone.  Here and there are pockets of soil in which shrubs and trees eke out an existence but most of the surface is bare limestone.  Rainfall is seasonal and can be scant, weeks, sometimes months, can go without measurable rain.   Temperatures can rise over 100F out in the plateau, I still remember my surprise (on a previous visit) when a thermometer I carried with me on a walk during the hottest time of the day measured 120 F.   The dominant vegetation on the plateau is shrubs, cactus and low trees.  There are places where the limestone has eroded to the point that sunken depressions have formed and accumulated a layer of soil where more substantial trees can grow.  But almost all of these depressions are small.  One of the largest one, the Bajura de los Cerezos has large trees and is moister than the surrounding terrain.  Domingoa in Puerto Rico lives in this severe but beautiful environment.

The last time I visited Mona Island, around 1996, I found many stemmed plants of Domingoa in the moister environment of the “bajuras”.  I had also found plants in the hot and very sunny plateau, but those were much smaller and much less common than the ones in moister surroundings.   In particular I found a good sized plant within easy walking distance of the camping area.   Sadly, the photos I took of the plant at this time were not good.

I visited Mona again between the 20 and 24 of July of 2012.  It was a wonderful experience.  One of the first things I did was to seek out the Domingoa plant to see if still survived.   I went looking for the place where I had seen it last and sure enough the plants were there.  I was dismayed by the fact that all the plants I found had developing buds or spent flowers.  Not a single one had an open flower.  However, one of the nights there was a spell of rain, the next day I found an open flower.  The plant I found had five inflorescences, one with a newly opened flower another with a bud just opening and one with a tiny developing flower bud.

Unlike many orchids Domingoa is pretty secure from collecting pressures.  Most of the island is off-limits to visitors and, even in those places where hiking is allowed, high temperatures, fierce sunlight and hordes of mosquitos tend to keep away all but the very hardiest of hikers.  I don’t know if Domingoa plants are in cultivation on the island of PR, I don’t recall ever seen plants exhibited in local orchid shows.  Domingoa haematocheila is reported from Cuba, Hispaniola and Puerto Rico. Ackerman in  his book An Orchid Flora of Puerto Rico and the Virgin Islands reports that the forms from Mona are vegetatively much smaller than the forms from Cuba.

Bulbophyllum sumatranum

I brought this plant in the summer of 2011 from a vendor in Hawaii.  It arrived in excellent condition with nice plump pseudobulbs and immaculate leaves.  I put it in my terrace and waited for flowers, and waited, and waited.  The plant stayed the same for the rest of the year.  Given that it was an adult plant I had assumed that it would bloom in the summer as do many Bulbophyllum.  I gave routine care to this plant for the rest of the year with little evidence of any effect, good or ill.  In late April 2012 I started watering it almost daily with a weak fertilizer solution.  I did this because almost all of my Bulbophyllum start producing new growths during March or April which locally is the second half of the dry season.  In late April sumatranum finally started producing a new growth.  The new growth came out of a pseudobulb that is part of a chain of pseudobulbs that escaped from the pot and are growing in the air.  Nevertheless because of the frequent watering an local high humidity it is growing quite well.  In the second week of May I was delighted to find that an inflorescence was growing out of one of the older pseudobulbs.  In May 16 the flower opened.  So far the plant has only one active growing point and one inflorescence but I expect that as the season progresses more vegetative, and hopefully, floral buds will start to develop.

Dendrobium anosmum and its relatives, the rest period as a tool to promote abundant blooming

Dendrobium primulinum stems at the tail end of the growing season

The same plant as above after two months of no water or fertilizer and exposure
to bright light.

Dendrobium Adrastra blooming from leaveless canes

A properly rested plant of Den, anosmum with more than forty buds in a single cane.  Note the blooms are produced all along the lenght of the stem and not just near the tip

A relatively young Den. primulinum plant, note that stems are plump and still have the remains of a few leaves.  See below the plant in full bloom.

Giving your Dendrobium a rest period can be the difference between an impressive and abundant floral display and one that produces just a few blooms.  Species of Dendrobium of the group that includes  anosmun, primulinum, cucullatum, nobile and parishii among others flower best when given a rest period that mimics the seasonal conditions that are the trigger for blooming in their native haunts.

What is the nature of the seasonal rest period in this particular group of orchids?  These Dendrobium live in the south east of Asia and in parts of India.  In these regions they are subjected to the monsoon weather system.  In the summer there is abundant rains that fuel the growth of their long pendent canes.  But as winter approaches the rain diminishes considerably and eventually ceases for some months.  The constant cloudiness of the monsoon season is then substituted by clear sunny skies.   As the rain ceases the trees lose their leaves and the Dendrobium are exposed to high levels of sunlight.  Finally as the dry season starts the Dendrobium lose their leaves and enter the dry season as a bundle of stems that not in the least resemble their lush rainy season appearance.

Generally, but not in every geographical region, the dry season is also a season of lower temperatures.  The combination of high light conditions, drought and low temperatures is said to prime the buds of the stem of many Dendrobium for flowering. That means that the seasonal change is the cue that makes the vegetative buds that are all along the stems turn into flower buds.   When orchidists talk about giving their plants a rest period they are referring to the set of circumstances in the natural habitat of the Dendrobium that I have outlined in the preceding paragraphs.

Personally I stop all fertilizing and watering in November.  This means that the media of some of my plants will become bone dry and stay that way sometimes for several weeks.  All my pendent Dendrobium tolerate these lengthy dry spells with little complain, probably because even thought they are not getting any water the environmental humidity is high enough to prevent severe shriveling of the canes.  However I do have to confess that if I see a plant becoming excessively wrinkled from desiccation I do water it lightly.

 Although these conditions might seem severe and some of these pendent Dendrobium will flower quite well without experiencing the most severe rigors of the rest season other species will not produce flowers if not given a distinct rest period.  The best example of an orchid of this group that grows very well and yet blooms poor in the tropics is Dendrobium nobile.  If maintained under constant warm conditions, fertilized all year and kept under shady conditions most nobile will bloom poorly and may not bloom at all.  

Some orchidist just can’t resist the urge to water and give fertilizer to their plants year round. These orchidists generally have a tough time getting blooms out of them.  I have seen massive nobile specimens that have never produced a single flower.  I once brought a large plant for the ridiculous amount of $15.00 because the garden store owner had become tired of waiting for it to bloom and felt the plant was taking too much space and not bringing any profit.   I gave this plant a proper rest period and the plant responded by producing 150 large and fragrant flowers in about twenty canes.  All those canes that had accumulated without blooming for years produced flowers all at the same time.

I know some people keep watering their plants even in the rest period and that some of those plants bloom from canes that have kept their leaves.  But so far I have not seen a plant that has kept its leaves bloom as abundantly as one that has lost all its leaves due to the stress of the rest period.

Calanthe rubens and Cal. Grouville two terrestrial orchids that are relatively easy to culture

Calanthe Grouville a hybrid

Calanthe inflorescences cascading from my terrace

Here you can see the way the flowers of Calanthe Grouville change color in my garden

A large plant of Calanthe Grouville with inflorescence

Calanthe Grouville plant with inflorescences that have been blooming for months

Plants ready for repotting, you can see the new buds at the base of the pseudobulb, for more details see text

This pesudobulb has two developing buds

Calanthe rubens

A mass of Cal. rubens inflorescences

Here you can see the shape of the Cal. rubens pseudobulbs

From what I have read about the start of the orchid hobby in England in the nineteen century, it seems the genus Calanthe was widely grown and much admired. In fact the first orchid hybrid to bloom, although not the first one ever made, was Calanthe Dominyi (Cal. masuca x Cal. furcata). Nowadays Calanthe has become rare in the orchid market although it still possible to find hybrids and species if one searches for them hard enough. But in Puerto Rico Calanthe has never been a popular genus and most orchidists are unfamiliar with even the most common species. I will detail my own experiences with this genus and why I think it is not favored among local growers.



The genus Calanthe has two group of species, the evergreen and the deciduous ones. General guidelines for the culture of both groups are similar in some respects but their biology also makes up for some major and striking differences. I have never grown evergreen Calanthe and I have never seen them shown in local orchid shows so I cannot comment about them. Those evergreen species I know from the literature hail from temperate climates and probably would die if kept at the tropical temperatures of the island of Puerto Rico.


My experience growing Calanthe has been with a deciduous tropical species and a hybrid of the same type. The species is Cal. rubens, the hybrid is Cal. Grouville. Calanthe rubens produces small pink flowers over a period of a few weeks in an erect inflorescence. Calanthe Grouville produces flowers that are somewhat larger than those of the preceding species and that are white and red. I my locality, and I don’t know if this is true elsewhere, the flowers of Calanthe Grouville start turning pink as they age. The flowers of Cal. Grouville open over a period of months on a single inflorescence that arises from the base of the pseudobulb.


Let’s start with the species, Cal. rubens. I suspect that the seasonal growing and resting cycle of this species is probably the source of confusion and frustration to orchid growers whose whole experience growing orchids is circumscribed to growing ephyphitic orchids such as Cattleya, Dendrobium and Phalaenopsis. The reason for the confusion is that for part of the yearly cycle of this species the plant discards both its leaves and the root system. The pleated leaves that looked so elegant earlier in the year start to deteriorate as soon as the inflorescence becomes close to blooming and become yellow and fall just as the first flower is opening. This seems to be a source of distress for those orchids growers unfamiliar with this plant and some assume the plant is sick and is going to die. The fact that the leaves of Calanthe tend to look awful and the end of the growing cycle, even before they are shed is also something that doesn’t endear it to growers that prefer clean and immaculate leaves on their plants.


Cal. rubens blooms at the start of the year in my garden, plants bloom between January and February. In this stage of their yearly cycle they are normally composed of an older pseudobulb and the current year’s growth with a single inflorescence arising from the base of the newer pseudobulb. The plant has neither leaves nor roots and the pseudobulb supplies all the needs of the inflorescence. At this time I water my plants but the plants seem to survive equally well with no water at all. I water them to avoid having the pseudobulbs become too withered. When blooming is getting close to finishing a rapidly growing bud will appear at the base of the newest pseudobulb. This is the signal I use to repot the plants. I take the plants out of the pots, I trim the old dead roots but leave the base of the roots still attached to the pseudobulb to help anchor the plant in the new potting media.


The plant should be repotted just as the new growth starts developing its roots. I tend to repot at an earlier time when the new growth is pretty small but I do this mainly because I have on occasion damaged the new growths when I have waited too much to repot them and they are quite large. I have used several types of media such as potting soil, peat, compost, sand and I have not noted much difference in the growth response of my plants. However there are two things that seem to have a great influence on the growth rate of the plants. First is the inclusion of manure in the potting media. If the media is around 1/3 manure the plants do much better. You might want to ask, Isn’t that a lot of manure on the media? The answer is, yes, but that what works for me. Second if the media is loose and easily penetrated by the roots the plants grow more vigorously. Calanthe in compacted hard to penetrate media produce smaller root systems and stay smaller than those grown in fluffier media. When the plants are in full growth mode I give them daily watering and in those cases when I have a large pot full of pseudobulbs I will even go so far as to put a water dish under the pot to ensure that there is enough water to sustain their rapid rate of growth.


I divide my plants every time I repot them, Calanthe is one of the few orchid genera where a single pseudobulb can produce a new full sized new pseudobulb without the back up of older bulbs. Depending on my mood I might plant them one bulb to a pot, two or even a dozen in a single pot. If they receive the proper level of light and watering they will do well in any number of combinations. I don’t give them the water soluble fertilizer when I water them since the manure in the potting mix takes care of their fertilizer needs for the whole growing season.


My plants produce their growths during the summer when local temperatures can climb into the nineties and it rains almost daily. They bloom in the colder and drier part of the year when a whole month can go without significant rain.


They get full sun most of the morning and shade from 11:00 am on. Exposure to too strong sunlight burns the leaves and leaves them covered with bleached yellowish areas and dead spots. But plants grown in the shade are weaker and bloom poorly. It takes a bit of experimenting to determine which exposure best suits the plants in your location. I try to achieve the elusive slightly yellowish and yet not covered with dead spots areas that brings the best blooming results in my area.


I treat my Calanthe Grouville the same way as Cal. rubens but since the pseudobulbs are much large I make allowances for a larger adult size. Cal. Grouville can form large avocado sized pseudobulbs and produces beautiful pleated leaves. It grows enthusiastically under tropical conditions and sometimes produces two growths at the same time from a single pseudobulb. Its inflorescences can get much larger than those of rubens reaching a meter or more. It produces its relatively short lived flowers in sequence as the inflorescence elongates. The inflorescence can have one to three flowers at a time. My personal problem with Cal. Grouville stemmed from its proclivity to proliferate at a furious pace if given good care. Since every year the number of pseudobulbs duplicate I found myself with dozens of plants. Because these plants are not small, finding a place to put them became a chore. I recall one year that I had so many that I gave every member of my orchid society a pseudobulb to plant and grow.


Cal. Grouville can stay in bloom for months but the inflorescence is at its most beautiful when it is opening its first few flowers. Afterwards it becomes leggy, in some cases the inflorescence can arch downward and eventually reach the ground which doesn’t stop it from continuing to bloom. This Calanthe is particularly striking in massed displays in which many plants are shown together.


My Calanthe seem impervious to most diseases but sometimes the pseudobulbs can rot if kept too wet when they are supposed to be in the dry season. One peculiarity of these plants is that sometimes the pseudobulbs produce small plantlets from their tops. Calanthe rubens pseudobulbs have a constriction in their top half, this makes the top half vulnerable to snapping off from the plant if the pseudobulb is handled too roughly. But if this shouldn’t cause alarm as the snapped top can be planted on its side and it will eventually produce a plantlet from its top that can be reared without difficulty.