Dendrobium densiflorum revisited, the March 2011 blooming

Photo taken using sunglight 

Freshly opened inflorescences photographed under sunlight

Four day old inflorescences photographed with flash.  The fact that local temperatures have been significantly cooler than the norm has meant that the flowers have held up well and may last more than a week.

This is the 2011 blooming of my Dendrobium densiflorum.  It produced four large inflorescences, because of the way they were in the canes only three can be seen.  This plant has continued growing in size since I wrote about it back in 2008.  Good management when it is producing its new growths, which need plenty of watering and fertilizer, has resulted in the plant producint the largest canes to date, some achieving a lenght of 20 inches (53 cm).  Although this orchid has been at times an erratic and shy bloomer, a winter with unusually cool temperatures for our locality stimulated four of the canes into blooming.  The cooler temperatures have also helped extend the life of the flowers.  This plant is very pot bound and has been in need of repoting for some time now, but this is something I must confess I dread as this plants greatly resent root damage and can sulk or even die from a too rough repotting.  I have moved the plant indoors as thrips are driven insane with desire by the sight of this flowers and will flock to them in great numbers and damage them in short order.  Rain can also damage the flowers.  Sudden exposure to higher temperatures can cause premature wilt in individual flowers of the inflorescence which can spoil the look of the same.  I saw a number of seedlings of this species for same at the 2011 Puerto Rico Orchid society orchid show in March 17-20.  I wonder if in a few years there will be more plants of this species blooming locally.  I recall that in the nineties in every spring show you could see plants of Den farmeri, Den palpebrae and even Den. densiflorum (although this last one was the rarest of the lot).  Nowadays all you see in local shows of this type of Dendrobium are plants of Den, farmeri var. albiflora.

Someone asked me why grow plants with such short lived flowers.  The flowers of this species can be short lived, but during the time they are in full bloom they are so beautiful they outshine everything else.  The japanese people have a concept where certain things are beautiful because they are transcient.  Then these flowers have double measure of beauty, they are transcient and also beautiful on their own right.   This concept of fleeting beauty can be seen on the poem of Kokan Shiren (1278-1346) a poet and Zen Master This poem was written after a large earthquake has struck the part of Japan where the poet lived.

Still things moving,

firm becomes unfirm,

land like ocean waves,

house like a boat --

a time to be fearful,     

but to delight as well;

no wind, yet the wind-bells

keep on ringing.

Epidendrum nocturnum, a night fragrant orchid native of Puerto Rico

This cleistogamous flower was opened to show the flower structure inside the unopened bud

See developing seed capsure at the lower right corner

Epidendrum nocturnum is an orchid with a very large geographical distribution.  It can be found in Central America, the Greater Antilles and tropical South America.  In Puerto Rico it is reported as growing in the coast as well as in the high peaks in moist areas in the east of the island.  All the plants that I have seen have been in the middle to high points in the Sierra de Luquillo.  There are three orchids in the Sierra de Luquillo that have very similar flowers, Epidendrum nocturnum, Epi. carpophorum and Epi. tridens.  Epidendrum capophorum is so distinctive in its vegetative form that it is easy to distinguish from the other two.  Distinguishing between Epi. nocturnum and Epi. tridens it’s a bit harder but adult plants can be told apart because of the larger size of Epi. tridens.

In favorable habitats Epi. nocturnum is not rare, unfortunately I have yet to find a non cleistogamous plant.   A cleistogamic plant is one that self fertilizes. In some cleistogamic species the flowers never open.  This is the case of the Epi. nocturnum that I have found in the wild.   There are several species of orchids in Puerto Rico that are self fertilizing.  Why do plants do this?  There is a theory that says that cleistogamy allows plants to colonize areas where their natural pollinators are not present.  There are a number of species of Puertorican orchids that are pollinated in the continents by insects that are not present in the island.  A good example is the genus Dichaea, in those areas of South America where they grow they are pollinated by Euglossine bees, these bees are absent from Puerto Rico and yet local Dicheas reproduce well enough without them.  In these species cleistogamy is suspected even in those cases where the flowers open fully.

I have seen this plant growing in boulders in the middle of streams and in the trunk of tree ferns and Sierra Palms.  One interesting detail is that the healthiest plants all were growing in areas where there was an opening in the canopy.  These openings in the canopy could be in the middle of a river, in an area where a landslide or tree fall allowed the sunshine to penetrate into the forest and in the areas bordering roads.  This tells me that this plant grows best if it received bright light which may include being exposed to full sun for some time during the day.

The presence of seedlings growing under the cleistogamic plants show that this strategy is fairly successful locally.  This plant has a delightful perfume that is produced at night.  This plant is grown horticultural but all the plants I have seen in cultivation have been produced commercially outside Puerto Rico.  I was pleasantly surprised to see seedlings of this species for sale in the 2011 Puerto Rico Orchid Society annual orchid show.  The easy availability of plants produced in captivity, and the general absence of this species from most orchid collections probably means that wild collection of this species in Puerto Rico is apparently very rare.  I have yet to see plants of this species exhibited at orchid shows, the reason is not clear but it may reflect a preference for showing flowers with larger and more brightly colored flowers rather than any particular rarity of the species in captivity.

You can easily see the massive root system of this plant

I recommend this orchid for those people that place a great value in the fragrance in orchids.  I have not cultivated this plant but from observations of its habitat I would think this plant needs regular watering, high enviromental humidity and bright light to do well.  In all cases where I have seen this plant growing the roots were exposed to the air which indicates that this is a plant that needs an open, airy media to do well if grown in a pot.  Another alternative is to grow it mounted on a slab or plaque.  The downside of growing this it mounted is the need for copious watering during the peak of the dry season to avoid the death of the plant from dehydration.

Arundina graminifolia an exotic orchid that has become naturalized in Puerto Rico

A flower of the most common form

A flower of the dwarf form

A flower of the dwarf form in the middle of a group of canes of this orchid

A side view of the flower of a form that seems to be uncommon in the extreme

Excuse me for the poor photo but it is the only front view I have of this mysterious flower

Arundina graminifolia is an orchid native of Southeast Asia that has become naturalized in Puerto Rico.   It can be found in the wild from Sri Lanka and India on the Indian Ocean to the Caroline Islands and Tahiti on the Pacific Ocean.  It is a vigorous plant that has escaped cultivation in areas outside its natural geographical range for example the Hawaiian Islands and Puerto Rico.  In Puerto Rico it has been reported from moist areas in the east of the island.

I have seen it growing in gardens all over the island sometimes forming huge specimen plants.  The tallest plants I have seen were in cultivation right on the ground in gardens in the foothills of the Luquillo Mountains, some seemed to be close to seven feet tall.  There is a huge specimen plant growing in a garden that sits by the side of the road that goes from Utuado to Adjuntas that is notable due to the large number of flowers it can have at the same time.  The plants are known locally as bamboo orchid due to a fancied similarity between the tall canes of this orchid and the canes of the bamboo plant.

I have seen several variations of this plant growing in captivity.  The most common form of Arundina in Puerto Rico is the tall one that can grow to six feet or more.  This form is nearly ubiquitous in the gardens of orchid growers.  However a dwarf form has become very popular in the last few years and it not rare to see this form growing as a pot plant.  It can also grow into a large clump of stems but since it is just a few feet tall even large clumps can be accommodated in a limited space.  The flowers of the tall type and the smaller type are quite similar, they differ mainly in the way the flower are presented and in some details of structure of the lip.  In its native haunts there are several varieties that formerly were classified as different species, these are now considered variations of a single species. Recently a white flowered form is sometimes being offered for sale at orchid shows but I have yet to see one blooming in a local garden.

Intriguingly there is a fourth type of Arundina in Puerto Rico.  The lip of the flowers of these plants is very different from the two more common types.  I have searched to see if this type of Arundina has been reported elsewhere but so far it has been absent from the books and Internet sources that I have accessed.   As far as I know this mysterious Arundina type is not in wide cultivation and I have seen mature plants of this type only in one private garden.  I was told that this type of plant was found in a population of feral plants in the south east of the island.

This orchid is easy to cultivate in Puerto Rico and responds vigorously to good care.  To cultivate this plant you need a eight or ten inch wide pot to accommodate its rampant growth.  The media should be coarse and heavy to avoid having the pot tip over.  Cow manure is an excellent additive as a top dressing to the media in the pot.  You need to water this plant abundantly as this helps the plant achieve its tallest size.  Large vigorous plants can produce single or branched inflorescences that can produce blooms sequentially for weeks or even for months.  When the inflorescences stop producing flowers they produce small plantlets.

These little plants can be detached when they stop growing.  I put them in water to stimulate the production of roots.  When the small plants have several roots they are transplanted to a pot with a mixture of potting soil and compost that is kept moist until the plants have been able to develop a significant root system.  This plant root system tends to be superficial so when growing the tall type in a pot it is useful to have a stake in the pot to tie the canes.  Young canes don’t need staking to stay upright but canes seen to become weaker with age and prone to tip over. Once the plant produces its second cane it can be treated as an adult plant.  Unlike most orchids this one is easy to grow into a specimen plant in a comparably short time.

Vanilla claviculata, an orchid species endemic to the Greater Antilles

Only a single flower is open at a time

The lip is waxy and heavily hairy and sculpted

Side view of the flower, note the dense undergrowth where this plant grows

A weak inflorescence in the middle of a landslide area where the substrate is bare rock

Flower buds in various stages of develpment

A  seed pod which is known in horticulture as a bean

Vanilla claviculata is found naturally in the wild only in the Greater Antilles.  In Puerto Rico I have unequivocally identified it only in Maricao.  Unfortunately I can’t say where I have seen this plant aside from the spot where I found the plant with flowers because I am not familiar with the characteristics that distinguish one species of leafless Vanilla from another.   To makes things worse this species occurs simpatrically with another species of leafless Vanilla, and they sometimes hybridize giving rise to plants with flowers with intermediate characteristics.

The plants I found in flower were blooming in the summer.  For me one of the most vexing things about local Vanilla orchids is the difficulty of finding plants with flowers.  I have walked many hours through forests in Aguadilla, Guajataca, Maricao, Rio Abajo and Susua where Vanilla grow wild and seen areas literally carpeted with Vanilla vines which also draped trees nearby tree and any supporting object, but there wasn’t even a single flower in evidence anywhere.  From time to time I would find the odd spent inflorescence and in even fewer occasions the bean, but finding plants in bloom has been a thing that has mostly eluded me.  I have on occasion seen plants high up in the canopy that might have flowers but the height of the trees precluded any access to the flowers if they were present.

In local forests it can difficult to predict where Vanilla can be found.  I have seen them growing with the same gusto in intact primeval forest and in landslides where the forest was ripped down to the bedrock.  However those species with leaves seem to be confined to relatively intact primeval or secondary forest while those without leaves seem to be much less fastidious on where they grow.

In Maricao I have seen the leafless type grow from the edge of the forest into landslide areas that consists of little more than exposed rock.  As a result you can see vines that extends for dozens of feet into a bare area.  In spite their poor appearance they seem to be surviving quite well in this very sunny environment.  One good place to see this is the road that crosses the Maricao forest.  But don’t expect to see flowers.

The flowers are light green with a massive lip and measure between one and half and two inches.  The lip is waxy, hard and brittle, considering the texture of the lip you would have expected this flower to be longer lasting.  But as other Vanilla these flowers only last one or two days days in good condition.  In the place where I found the flowers there were many inflorescences a reversal of the usual situation.  But most of the inflorescences were confined to an area where the floor of the forest was carpeted with water holding bromeliads.  I don’t know if the presence of the bromeliads is significant or just a coincidence but there may be a clue there that might help with blooming this species.  The patch were the flowers were found had another interesting characteristic, it was chock full of other orchid genera, growing cheek by jowl in this small area.  There are in the area plants of Eltroplectis, Epidendrum, Pleurothallis, Polystachia, Prosthechea, Oncidium and Vanilla.

This plant produces seed pods that can be used to produce vanilla.  However the vanilla from this species is considered of inferior quality to that produced by pompona.  Seedpods in this species are produced rarely but they are way easier to find than flowers and you can occasionally spy them in one or twos hanging from the spent inflorescences.

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.