Dendrobium Culture: Making a Den cretaceum specimen plant

 

Some years ago, I started cultivating a Dendrobium cretaceum plant with the aim of eventually getting a specimen plant with many flowers.  For aesthetic reasons I decided to cultivate the plant so that the canes hang from the bottom of the basket.   The orchid is planted in a way that is extremely different from what is the usual way of growing Dendrobium.   The plant was originally attached to the center of the bottom of the basket.  That way the roots would grow up into the potting mix and the canes would grow downward.   That is the exact opposite of how these plants are grown.    The basket is six inches wide and three and a half inch deep.  The potting media is bark, and fills the basket to a depth of two inches.   Den cretaceum is not a big plant so this arrangement allows plenty of space for it to grow for years.

There two-inch layer of media in the basket allows for plenty of air to reach the roots.   This is a very important detail.  You would think that is a very small quantity of media for a plant that one eventually wants to become large and bushy.  But due to the local climatic conditions it is the perfect amount.  The reason is that during summer and fall in my locality it rains almost daily.   At the peak of the rainy season the media can stay wet for weeks or months.   In a plastic pot this would mean a waterlogged media that would quickly become devoid of oxygen, will start rotting and turning into slush under the influence of fungi, bacteria, high temperatures and fertilizer.  

 To my delight, at the start of the 2023 growing season the plant, that usually produces four or five new canes every year, in a fit of exuberance, started producing nine new canes.   This is wonderful but it bring its own suit of problems.   First, all the canes are clustered and oriented toward the strongest source of light.   That means that the plant is self-shading.   This can result in that some of the canes will be spindlier and weaker.   To avoid that I moved the plant to a spot where it gets the strongest sunlight I can give it without burning the leaves.  Eventually as they grow the canes will spread out and the issue will resolve itself.  Because of the particular way the canes of Den cretaceum grow the leaves are not particularly vulnerable to burn if exposed to strong light.  The canes of this orchid arch downward, so that when the sun is at its strongest the leaves are edge on to the light.   A note of warning, while canes are capable of taking full sunlight, the base of the canes are prone to burning if exposed to very strong sunlight.  Fortunately, this is not a problem for me since the basket protects the tender bases from the sunlight.

If all goes well, by the start of the 2024 dry season, the canes will have reached their full size.  When the canes reach full size, I stop watering and fertilizing the plant, it gets only the scant amount of rain we get during the dry season.  The plant loses all its leaves and looks dead for a time.   In April I will start looking for the swelling flower buds along the length of the canes.  Then in May I expect the plant to produce a mass of flowers.  You can see on top the 2023 blooming.   The plant as it is now is in the photo below.

Tetramicra elegans [Hamilton] Cogn. 1910, here I show the flowers of a plant from cultivation, origin unknown and two flowers from plants "in situ" in the Sierra Bermeja, Puerto Rico

Cultivated plant

Cultivated plant

Cultivated plant

"in situ"

"in situ"

Tetramica elegans is an orchid that is native of Puerto Rico and can be found in dry forests in the southwest of the island.  Because it has showy flowers it also cultivated by orchidists.  The photos of the plant in cultivation are from a specimen plant that produced large, many flowered, even branched inflorescences, something I have yet to see in the wild where most of the plants I have found are small and have few flowered inflorescences none of which has been branched.  The flowers of the cultivated plant are fuller, larger and more numerous than those of the wild plants.  I cannot say that this is due to some genetic condition or caused by optimal care for the cultivated plant.  The lip of the cultivated plant seems to have a pure white central stripe, but it does have a faint yellow spot in the middle.  Sadly, the friend that cultivated this plant died some years ago I can't ask him where he got the plant.  The plants from the wild are part of a large population on the Sierra Bermeja hills in Cabo Rojo.

Bulbophyllum longissimum, like slender and delicate pink tentacles of Cthulhu

Freshly opened flowers

Fully opened flowers

This orchid is found in Thailand, Burma and Malaysia.  The flowers of my plant open at ten inches long and eventually elongate to eleven.  It has proven to be easy to care for and trouble free, probably because the local weather and altitude are similar to those of its natural haunts.  Initially it was a bit of a slow grower, but I think this was because the plant was small.  After its pseudobulbs achieved adults size it has started producing side branches.  The flowers last for about a week in good shape and then start to deteriorate.

Here are some details on the weather and how I care for my plant.

Media: fine bark.

Potting:  It is growing in a eight inch wide home-made wire metal basket.  The plant grows on top of the basket but it is starting to climb down the sides.

Watering:  During the summer this plant gets rain every single day in the afternoon, the media stays constantly wet for months.  During the dry season, if it is not growing it gets a soaking once a week or a bit more frequently if the bulbs start to become furrowed.

Humidity: The local weather provides the right amount of humidity for this plant most of the year.  Humidity locally fluctuates between 70% and 90% during the day.  At the height of the dry season humidity might go down to 50% for a few hours a day but climbs over 70 at night.  At the height of the wet season it can stay close to 100% during the night.

Fertilizing: A fertilizer with a high nitrogen content,  two times a week when it is producing new growths.  I stop fertilizing when the new growths achieve mature size.  I don’t’ fertilize if the plant is not producing either new growths or roots.

Light: It gets bright light, it is with my Cattleyas, it gets full sun early in the morning and the rest of the day it is under the shade of trees.  It is not in deep shade.

Temperature: From 95 F high day to 75 F at night during the summer, 80F to 60F during the night in winter.

Care: Under my conditions, this plant thrives with routine care.

Pests:  None so far, insects have not attacked the plant, it is in a place innacesible to slugs, and fungus and bacteria have not been an issue.