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This little equitant Oncidium was found in the same general area as P. macconnelliae, however it did not seem to be as common, possibly because the meter long flower spikes of the latter made finding it easier. |
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These little plants had been placed onto the root masses of the Epi. ciliare growing on a few trees around the Guana Island hotel fairly recently. Here they became established and gave a clear view of growth habit. Out along the trails the plants were most usually found in large, well established clumps making observation of growth habit more difficult.
From observations on my own purchased seedling, coupled with those observations made on Guana Island, it appears that small immature plants only produce a very few side fans, and instead of forming clumps the plants freely produce keikis (asexually produced baby plants) off of vertical flower spikes. This way the plant will "walk" up the trunk of the host tree. If the roots of the growing keiki do not contact the host tree above the mother fan, the weight causes the spike to arch down increasing the probability that the keiki roots will contact a branch, or the trunk at a level below the mother plant. there may be a cascading daisy chain of keikis growing upon the flower spikes of unrooted keikis. In each case, if my memory serves, the keikis, no matter how old only consisted of a single fan
Although the plant was seen growing well and flowering in full sun around the hotel, it was mainly encountered growing on/covering a few "orchid trees" in less open, lightly forested areas of the trail. In these areas only a single flower was seen, whereas in the sunny areas flowers were fairly common, although not abundant, even though July is not the flower season.
All of the plants seen were emaciated, even those in bloom. Those in full sun were light yellow green in color. The largest fans encountered had leaves up to 5-6 inches long.
Observations and a Hypothesis on Germination of Guana Island Orchids - Where found, the orchid plants on the island seemed to be grouped in small areas, with individual plants no more than a few meters from one another. This suggests that most of the recuitment is local, and dispersal of seeds is in general low. This makes sense simply from the dilution factor associated with distance from an opening seed pod.
- The probability of favorable conditions for seed germination and early development being present on those surfaces where orchids were seen (rocks, smooth barked tree trunks, and cacti stems) seems low. However, large bromeliads/ Tillandsia spp. were extremely abundant in those areas where orchids were found. The old holdfast/root masses were present very near to most orchids, and although time did not permit me to examine clumps of orchids in detail is seemed as if clumps may have been established on these old holdfasts.
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It would not be surprising that the remains of the bromeliad roots could rarely be discerned among the roots of an orchid since the roots would quickly form a moist/humid micro climate that would speed breakdown of the holdfast through decay and termite/insect activity. My hypothesis is that the holdfasts are almost necessary for orchid reproduction in this habitat. They would both catch the dust like orchid seeds washing down the tree trunks and create a moisture retentive medium for germination and early growth. |
Seeded Spike   |
The bromeliads are ubiquitous in all forms from small seedlings to decaying root holdfasts (as can be seen in the preceding images). They attach and grow on all types surfaces from bare rock to the thinnest twigs. The large adults, up nearly a meter tall, produce large, two meter long flower spikes. The silk tailed seeds are carried by the wind and coat nearly every thing in vicinity of the mother plant.
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