Winter in India mostly occurs from December to February, the year's coldest months are December and January. India is home to an extraordinary variety of climatic regions, ranging from tropical in the south to temperate and alpine in the Himalayan north, where elevated regions receive sustained winter snowfall. Generally temperatures between 18°C and 28°C is ideal for most orchids, however an occasional short period exposure of 38°C or even below 5°C will not harm most orchids.
Phalaenopsis orchids will start initiating spikes if the night temperature drops below 18°C and your day temperature is not more than 26°C. Vandas and Dendrobiums are cold-sensitive and do not like the temperature to drop below 16°C and can be particularly prone to losing leaves when exposed to cooler temperatures. Seedlings and immature small plants are also much more sensitive to chills than mature plants. Keep the temperate growing varieties like Vanda and Dendrobium orchids in a brighter and warmer place.
The Catasetinae group orchids like Mormodes, Cycnoches, Clowesia, Catasetum and their hybrids can be ignored in winter completely as they go into a deep winter rest. Before the winter rest they go through an aggressive growing season, where they require a good amount watering and heavy nutrient feeding. These plants must be kept dry once the leaves are shed and sparingly watered once in 20 days or so.
When the temperature drops and days are short with reducing daylight, orchids will slow down the growth or even stops doing any activities. The amount of watering and fertilizing required during the growing season like spring and summer are no longer required during winter. Excess watering can accelerate the breakdown of organic growing medium like coconut husk or pine bark and can lead to root and plant rot. Also, excess fertilizer can accumulate in the potting medium, can burn plant roots and leaf tips.
Winters can become very dry, keeping the humidity high by using humidity trays, etc will help the plants. The good part of winter chill is that the cool periods help induce or enhance bud initiation and flowering on many orchids.
In brief, take care of the following:
- Water and fertilize less.
- Increase the light and humidity to compact the dry and cold conditions.
- Keep the plants away from freezing temperatures.
- Be ready for spring flowering season after winter.