When do I water my orchid? is one of the most frequently asked questions I would say with regards to orchid culture and would expect it to be too as it is a very important part of growing any plant never mind orchids.
The simple and most accurate answer would be ‘when the plant needs it’ but this wouldn’t be of any help at all if you don’t know when. Firstly you need to know the needs of the orchid in question as you cannot give the same watering schedule for example to a Disa and Cattleya, these are on opposite ends of the scale!
Once you have an idea of the conditions the orchid requires then you can try and implement it the best you can, with the majority of orchids it would be wise to let the potting mix slightly dry between watering especially with orchids with pseudobulbs as these have water stored, you are more likely to kill an orchid by over watering than under watering. And by over watering I mean frequency not the amount at any one time, I have a saying ‘ if in doubt leave watering out’. There are exceptions and Disa is one of these as they like moisture at the roots at all times and literally sit in water!
A good way to learn when to water is too get used to lifting the pot and feeling the weight, when light it is time to water. The use of clear pots is a very easy way to see when to water, you can also use a wooden skewer that you insert in to the potting mix which will water mark the skewer given you a indication whether to water or not. You can also insert a finger in to the potting mix or what I do on regular occasions is to carefully tip the plant out of the pot and inspect the mix and the roots. Over time you will learn when to water and simply putting it you will just know when to water, believe me!
It is also good to let the water that you choose to use to become the ambient temperature of the room the orchids are in to prevent shock and damage to the roots.