Saturday, February 19, 2011

Tolumnia (Oncidium) variegata, a native orchid locally known as angel of the coffee plantation

Tolumnia variegata from Rio Abajo

Note the large and prominent callus at the center of the flower

Two flowers from a Rio Abajo plant

This fan of four leaves produced an inflorescence that is astonishly disproportionate to the size of the plant.  It can be seen the lower two pictures.  This is a Rio Abajo plant.

The several feet long inflorescence carried the flowers high over the host bush
Tolumnia hybrid

Tolumnia hybrid

The previous Tolumnia hybrid flower produced after the plant was grown in high light conditions in my garden

A Rodricidium hybrid that has Tolumnia in his ancestry

This little orchid is among the most widespread species of orchid native of the island of Puerto Rico.   I have seen it in many places in the island, from the moist forests of the Northern part of the Karst area to the dry scrub in the south west.   I have also seen this orchid in the island of Hispaniola in Santo Domingo.  The carefully manicured shrubs in the area of the Japanese Garden in the world famous Jardin Botanico of the capital of Santo Domingo have in their branches a dense population of this orchid.  The density of plants I saw among the branches of some of the shrubs in the Japanese Garden is among the greatest I have seen in any epiphytic orchid, the plants were tiny, had four fat and short leaves and were blooming abundantly at the time of my visit.  I have also seen this plant in coffee plantations that are at middle elevations in the central mountainous area of Puerto Rico as well as in coastal forest that is still reasonably intact.
This plant has an equitant arrangement of the leaves, this means the leaves are arranged in a flattened fan shape.  One of the peculiarities of this species is that plant size varies wildly even in areas where you would think all plants would be closely related.  In an area of less than one acre in the forest of Rio Abajo in Puerto Rico you can find small plants with four short and thick leaves that produce two of three flowers and larger plants with longer leaves that produce disproportionally huge inflorescences with dozens of flowers.  The largest plant of this species that I have ever seen was growing in the Guanica dry forest.  I saw it when I was walking through a small ravine in the forest where conditions were slightly moister than in the surrounding forest.  Growing in the understory, among the slender branches of a tall bush the plant I saw had long and slender leaves about four or five inches long.  The plant was growing with its roots spreading in the air in all directions, unattached to anything, the plant was tangled in the branches by its long stolon which joined the newest fan with the remains of older leave fans.  It could have been that the plant had fallen from a high branch, gotten tangled in the low branches and had kept growing unfazed by its new circumstances.
But no matter the size and shape of the leaves the flowers of all the plants are nearly identical.  There some plants that have a pronounced lilac coloring in the lip and floral segments, but I have seen those only in photos, I have never seen one of this type growing in the wild.  The flowers are constant in size with the flowers produced by the tiniest plants being only slightly smaller than those produced by the largest ones.
I have seen plants of this species in bloom in March sometimes in good numbers in favorable habitats.  However they can be common in highly modified habitats such coffee plantations and I have found from time to time plants growing in trees and bushes in urban areas and even in a tree in the central plaza of a small town.
People often collect these plants and they are seen from time to time at local orchid shows with relative frequency. Any time somebody makes a display of native orchids in an orchid show that falls on their blooming season this orchid is almost sure to be a present.  Puzzlingly, in spite of this being a common orchid, it seems few people are adept at keeping them alive in a long term basis.  The very few that I have found to be successful with this orchid, were growing them in their native haunts in conditions that closely resemble what they experience in nature.  I have observed a few plants growing in the wild and the lifespan seems to be relatively short.  None of the plants I have observed lasted more than five years from the time I found them and some disappeared after only two years of blooming activity.
Tolumnia hybrids made with other species of Tolumnia are highly valued by orchid growers and are relatively inexpensive and easy to find.  The flowers of the hybrids are often vividly colored and sometime feature lurid color combinations arranged in stripes and spots in ways seldom seen in other similarly sized flowers.
I have kept many hybrids of Tolumnia and a few have survived for a significant period of time under my care.  All have eventually died, mainly of root loss but also from what appears to be fungal/bacterial infections.  My guess is that there is a key feature of their habitat that I have failed to replicate in a consistent manner.  Of those the plants growing in the wild that I had have the opportunity to observe over several years, the plants that survive the longest are those growing among the leaves of the shrubs in the top part of the shrub where they get bright light filtered through the leaves most of the day and probably a bit of full sun at midday when sunlight is striking the shrubs at its most vertical.   I suspect that the leaves of the host shrubs also provide a microclimate of higher environmental humidity that insulates the plants against desiccation.
Few orchidists locally cultivate this species, probably because it is just too drab when compared with the hybrids and the fact that they are neither prestigiously rare nor difficult to replace.  Most of those that keep these orchids do so by dint of cutting a branch of the shrub tree where they are growing in the wild and bringing it into their collections.  Many of the plants collected this way survive happily, at least for a time, in captivity.
If you want to try to grow this plant in the Island of Puerto Rico I would advice to grow it inside a leafy bush that still allows a significant amount of light to sift through its leaves.  A particularly good host is the Higuera tree.  But please don’t go stripping our State Forests of this orchids, there are probably plenty growing in private lands and in coffee plantations.  Owners of coffee plantations have been known to rip out these plants from the coffee bushes in the mistaken belief that they are parasitic and drain the coffee bush of vigor.

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