Dendrobium primulinum 'DeLeon' an interesting plant

Flower with nearly round lip

flower with a very small scoop like lip

Large flower with oblong lip that has a ridge in the middle

This is a flower that is just opening it will expand until it look that the one in the photo over this one

A fairly good blooming althought the presentation is not the best

Large plant growing in a fairly small wire basket

I brought this interesting Dendrobium a few years ago from Eli Orchids in Utuado, a town in the mountainous interior of the island of Puerto Rico. When I got this plant it was labeled as Dendrobium primulinum var. Leon and for lack of a better name I kept this ID and photos of this plant taken by me can be seen in several orchid forums. However when it bloomed the flowers were oddly different from what most books and Internet photos identified as typical primulinum. I found photos of flowers that had some resemblance to those of my plant, the flowers were those of variety Assamicum. However on closer inspection the resemblance proved to be superficial. Compounding the problem of identification was the strange proclivity of this plant to produce flowers of widely differing sizes and shapes. Even worse some flowers expand quite a bit and may look one way freshly opened and another after they have been open for a week. A few days ago, with the help of Brian Monk who answered a question I posted in the Orchid Source forum, I finally learned that the true identity of my plant is Dendrobium primulinum DeLeon.

But the doubt I had about this plant identity plant, when I first bloomed it, piqued my curiosity so I studied scientific descriptions of the flowers of primulinum to better understand this plant. What I found is that the appearance of the flowers of this species is more variable in color and shape than one would guess judging from the characteristic of those exhibited and grown in the United States. The plants in the US, at least judging from photos of collections and exhibitions used to be, until recently, relatively uniform in appearance. I would like to add that primulinum now has been lumped with cretaceum and the plants are called Dendrobium polyanthum.

The form of primulinum commonly pictured in those books and photos that have been available to me has thick, arched canes that are relatively short. The flowers in these plants have hairy lips of a light yellow color, the sepals and petals are varied shades of mauve. In the lip, usually to the side of the column there are purple lines that have a varying extent in different clones. I have occasionally seen plants of this type in local collections, but I have never seen one in bloom anywhere in PR.

About four years ago a new type of primulinum appeared locally. This new type was part of a huge importation of all types of Dendrobium for the spring show of the PR Orchid Society show. It is clear plants of this type were also imported into the US as photos of the flowers of plants of this type cropped up in the Orchid Source forum. This new type has large flowers with a beautiful bright yellow color covering the center of a white lip, the sepals and petals were a delightful soft pink. But this new plant didn’t resemble DeLeon at all. The vegetative parts of this plant were different from De Leon and the thick short canes of the primulinum I had known previously. This plant resembles those plants known in Japan as var. giganteum.

Information on primulinum DeLeon is pretty sparse. I did several Internet searched and frustratingly and vexingly the results of the searches were either posts that I had made about this plant on the various Internet orchid growing forums or the advertisements of the vendor that sold me this plant. Thanks to Brian Monk I learned that this plant earned a certificate of cultural merit for its owner back in 1968, the plant exhibited had 101 flowers.

My plants grow well without any special treatment but are curiously varied in their blooming. This is a bit surprising since all are descendants of the same plant. Some produce large flowers with huge round white lips other produce smaller flowers. At times a cane can have large flowers near the top and smaller flowers near the tip. The lips of some of the flowers are very round others are oblong and some even have a ridge down the middle. It is unclear what causes this variation in the flowers but in general older plants with several older mature canes produce better flowers than younger plants with just a few small canes. A peculiar characteristic of this plant is that the first few leaves of the new canes can have a bright reddish or purplish tint in the margins, this I have not seen in any other Dendrobium of this type that I have grown.

This plant doesn’t seem to need much rooting media to subtract enough water and nutrients to prosper an achieve a good size. One of my plant has six healthy new canes from three to four feet of lenght and several older canes all growing from a mass of media two inches thick and six inches wide. However it is to be noted that this plant gets drenched every day during summer and fertilized weekly for as long as the canes are producing new leaves. This plant usually finished its growth cycle October and starts shedding its leaves by November.

Some years the plants blooms wonderfully, others they barely produce one flower or two. But I enjoy so much the flowers when they are produced that I don’t mind the fact that some years some plant fail to bloom. I have been looking at the wonderful plants that have been awarded in Japan and I have realized that the flowers of my plants would look even better if I did some grooming of the canes before the buds open to prevent crowding of the blooms. I am looking forward to next year blooming to see if I can make the 2011 blooming the most beautiful and elegant ever.