Flowering in orchids

In nature the majority of orchid species flower only once a year. The flowering time may vary according to species and the climatic conditions of the area occupied by the species . So much so , there is no particular time of the year which can be quoted as the flowering time for orchids in general. But there are particular times of the year when a large number of orchids come into bloom all at once. As far as the South Indian species of orchids are concerned , there are two such peak periods in flowering time .

1. Immediately after the great force of the monsoon has abated , during the months of August and September, most of the terrestrial forms like Habenaria and its allies , Liparis , Malaxis etc., come into bloom. They send up aerial shoots with the first rain,which grow up rapidly during the two months of heaviest rainfall , produce flowers during August and September and by the time rain abates the aerial portions die down leaving the tuber to remain underground till next year. There are also several epiphytic orchids which burst into bloom with the first rains,e.g., Rhynchostylis retusa, Aerides ringens, Eria pauciflora , Bulbophyllym fischeri, Bulbophyllum kaitense , few of the Oberonias, Ceologyne mossiae, C. nervo, Aerides crispum, A. maculosum etc. Altogether more than 60 species of orchids flower during these months in South India .

3. The second peak in flowering affects mostly epiphytic species , and occurs during the months of March and April. This second gregarious flowering may be in response to the increase in temperature and sunlight experienced by the orchids in the wild . During summer months there is some amount of shedding of leaves by the trees even in evergreen forests as a protective measure against excessive transpiration through leaves. This increases the amount of sunlight falling in these species . Acampe praemorsa, Bulbophyllum firmbriatum , Bulbophyllym tremulum , Dendrobium herbaceum D. crepidatum ,various Luisia species , Vanda testacea ,Coelogyne odoratissima C. glandulosa , Trichoglottis tenera etc. are some of the species which come into bloom at this time of the year. Among terrestrial species Eulophia macrostachya , Acanthephippium bicolor, Eulophia nuda also flower at this time.

There are a few species of South Indian orchids which bloom in response to the cool nights of January and February ,e.g., Dendrobium heterocarpum , Bulbophyllum aureum , Chiloschista pusilla etc. Most of Neottieae , like Zeuxine , Anoectochilus , Goodyera , Cheirostylis etc., come into flower during this time .

Species like Dendrobium haemoglossum , Thrixspermum arachnites , Ephemerantha macraei etc ., flower periodically . In the case of the Malaysian species ,Dendrobium crumenatum , it has been reported that a sudden drop in temperature of 10 F will induce flower bud initiation .This may also be the case in the above mentioned species as well. In all these cases flowers last only for a brief period , a day or two.