Orchids can be found growing all over the world, with a few exceptions of course. They grow in temperate as well as tropical regions. Depending upon their natural home, every orchid is adapted to the temperature range of that region. So the orchids growing in temperate zones will be less tolerant of high temperatures while being able to handle lower temperatures. On the other hand, tropical orchids can efficiently handle higher temperatures though they may find it hard to cope at lower temperatures. The very hot temperatures can cause stress to the orchids. Let us see how.
How to know the signs to temperature stress in orchids?
1. Very high temperatures can lead to excessive water loss by transpiration in those orchids that are not equipped to handle high temperatures; this will cause the dehydration in the orchid. Leaves will lose their rigidity and droop, pseudo-bulbs will appear more wrinkled.
2. If the sun rays are hitting the orchid directly, especially the midday sun the leaves of the orchid can get sunburnt. The sunburnt leaves change colour as the excess light can break the green pigment of the leaves. They might take a yellowish tint, develop dark brittle spots or might turn purplish, and eventually, the leaf tips and roots turn brown.
3. Blooms of the temperature stressed orchid can get affected; as in bud fall and/or pre-mature drooping of flowers.
Till the plant has not reached a point of no return, we can save and help the orchid to recover, how:
1. Move the orchid to a shadier cooler place, with better air circulation and more humidity.
2. Assess the damage to the orchid. The completely damaged parts can be removed but this too can cause more stress, so be judicious in cutting off damaged parts. The severely damaged plant can be re-potting in previously soaked and properly drained potting medium.
3. Never over-water the orchid immediately after finding it in a dehydrated state. It will cause more harm than good, root rot is one of the more serious consequences. Just as it is in humans start with giving little but frequent water. Spraying leaves with water can help reduce transpiration (this helped me save my Peace Lily plant). The mounted orchid can be placed in an empty clay pot to maintain higher humidity in the microclimate around the plant.
4. Fertilization of a heat-stressed orchid needs to be done sparingly. Once the plant fully recovers only then start giving the normal level of fertilization. Avoid heavy fertilization, as this can lead to salt deposition on the growth medium which will change the pH of the medium and hinder water uptake by the roots escalating the stress.