Sunday, January 2, 2011

Spathoglottis plicata, a weedy invasive exotic orchid that can go viral on you.

A mature fully expanded flower

A freshly opened flower still in pristine condition

Notice the many seed pods

A small patch of fern prairie in the Rio Abajo forest showing about a dozen plants on bloom

The purple color form

The damage that the flower beetles inflict on the flowers is clearly evident in this photo
The first time I saw this species growing in the Karst region of Puerto Rico it was back on 2005, on the sheer wall of a haystack hill, these hills are called locally “mogotes”. At first I thought they were flowers of the fabled alba form of Bletia patula. But on closer inspection the flowers turned out to belong to a plant of Spathoglottis plicata with white flowers that was part of a small colony growing on a ledge just over a tiny water seep.

I wondered if I could ever find a plant of this species on a more accessible spot so I could photograph the flowers, little I suspected the enormous success this plant would enjoy colonizing the areas around the road. In the next few years I started noticing that the plants were popping up all over the place. By 2010 these plants have become absurdly common on the roadsides of the highway 10 to such an extent that continuous collecting by passerby doesn’t seem to make any noticeable dent in their numbers. I have been to some fern prairies where you can see hundreds of blooming plants and an uncounted number of smaller plants.

On first sight this degree of abundance is a bit shocking given what we know about the difficult odds that orchid seeds face in the wild. But when I examined the plants and their inflorescenses the reason for their abundance became clear. All the plants that had inflorescences were laden with seedpods and it seemed as if almost every single flower was either pollinated or had set seed by self-pollination. As a result of the heavy seed production the population on this fern prairie is broadcasting onto the environment a staggering, mind- numbing quantity of number of seeds. The consecuence of the massive number of seeds that the plants produce is that even if only one seed in a million survives to grow into adulthood to reproduce the population will thrive and grow.

One peculiarity I have observed in Rio Abajo is that the white flowered plants are taller and an order of magnitude more common than the purple colored ones. When I have seen them in the same areas, the white plants dominate the sunny centers of the prairie and the purples ones grow in more shaded spots and the areas where the prairie borders on the forest. Native orchids can be found growing in the same areas as the Spathoglottis but in comparatively tiny numbers. The purple and white forms seem not to cross as I have never seen any intergrades even when the plant are growing cheek to jowl.

In the Rio Abajo Forest Spathoglottis distribution seems related to human activity and the disturbance of the soil. I have not found plants of this species in pristine areas inside the forest, away from the roads. However I am still finding plants here and there in spots along the road that enters into the heart of the forest so it is probable that in the near future this species will be able to colonize new areas deep in the forest.

Generally I am against the collecting wild growing plants, unless for scientific or to rescue them from destruction, because this depletes the populations of our native orchids but in this case this is a moot point. This plant is not native and since it is a wildly successful invasive weed it is not likely to be affected in its abundance or capacity to spread by being collected by humans. But there is a different, unexpected reason not to invite this species into your orchid collection. The reason is related to this plant impressive ability to produce seeds.  You should also be aware that collecting plants in state forests is prohibited by law, even if they are obnoxious weeds.

The reason not to bring this plant into your orchid collection is that the seeds of this plant are much more likely to germinate and grow than any other orchid I know. Whether they are more viable than the norm or less fastidious in the choice of their fungal partner or simply because so many of them are produced but the consequences are the name no matter the cause. As a result of the amazing capacity of the seeds of this Spathoglottis you will start finding seedlings in the pots of other orchids, under the benches and on the flower beds in the garden. I am sure most people will be delighted to see a seedling orchid appear in their collection. But this delight disappears quickly when one discovers that seedling Spathoglotis are growing at rocket speed on the pots of that rare, finicky orchid that only grows, and slowly at that, if watered at dawn with water derived from dew drops gathered by hand after midnight from rose petals and that will die if subjected to the slightest disturbance of its roots.

I have had trouble finding flowers of this species in good condition in the wild. Almost every inflorescence hosts one or more flower beetles that damage and disfigure the flowers. The beetle populations seem to wax and wane so at times it is possible to find a few flowers in pristine condition, but most of the times I have visited the areas where this orchid grows virtually all the flowers were damaged to some extent. Isolated plants seem to fare much better in this respect as I have found a few with their flowers in fairly good shape. But the flower damage doesn’t seem to affect in the least the plant’s capacity to set seed and produce plenty of seed pods.

It seems the humidity of the soil or orchid media dictates whether this orchid can colonize a spot. In one of my relative’s garden the Spathoglottis seedling appear only in well watered orchid pots and in regularly watered flower beds. The rest of the garden remains free of their presence even in areas where one would have thought at first sight that they could do well.

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