Orchids are famous because of their flowers. Different orchids flower at different times in a year. A number of factors control the flowering response in orchids. Some of these factors are external, while others are internally guided (like the hereditary setup). Though, controlling internal factors is a highly specialised field, we can still control flowering by manipulating the external factors.
There is a fixed time of flowering for each orchid. This can be either pre-poned or postponed somewhat by controlling certain factors. These are:
• Nutritional status of the orchid, the consequent growth rate of the orchid has a major effect on the flowering response. For example, higher level of nitrogen fertilization in Cattleyas produces more number of flowers, when grown on bark media, while in Cymbidiums higher level of nitrogen produces more vegetative growth.
• Climatic factors responsible for flowering: temperature treatments(vernalization) and light period requirements. Temperature plays an important role in flowering. Those orchids which flower in summers require cold temperature treatment after an active growth season. That is the rest period accompanied by cold temperature promotes flowering in the coming growth season. Unlike other plants, flowering in orchids is promoted when day time temperatures are higher than night temperature. However, in orchids like Phalaenopsis day temperatures higher than 25 °C inhibit flowering. While, day temperatures lower than 25 °C with even cooler nights promote flowering. Miltoniopsis flowers when exposed to lower temperatures of 15C accompanied by shorter day light periods.
The amount of light the orchid is getting also contributes to flowering. The plants which flower in summers require longer light hours and are called the long day plants. The orchids which flower in winters are the short day plants. In other words, long day orchids require shorter nights while short day orchids require longer nights. The problem with short day plants is that if their nights are interrupted with short bursts of light, flowering is inhibited.
Thing to be noted:
If your winter orchid flowering is growing inside and it does not flower. Then, may be the flowering is getting inhibited by switching on the lights of the room at night!
• Chemical factors affecting flowering in orchids are the plant hormones like gibberellins (GAs) and cytokinins.