What is the ideal water temperature for miltoniopsis orchids when watering? does warm water apply to all orchids or cool growing orchids require cool water?
I certainly don't adjust my water temperature according to the night temp requirement of the plant! I do temper my water when I am using tap water in the winter so it isn't cold, but more like room temp). In the spring/summer/fall, I am using rain water which is essentially room temp.
It's a great question and I look forward to hearing others' opinions
I use an aquarium heater to heat my water. Its in a 2 gallon watering can and heats up very quickly.
Water out of the tap is far too cold, and its also wasteful getting warmer water ( running the hot water tap ).
I also like to let the water stand about 24hrs to dissipate chlorine.
I use this water on all my orchids - including milt seedlings- regardless of whether they are cool to warm growers. They are all doing well.
Interestingly my orchids outdoors for the Summer only get rainwater - which is fairly cold, and they are fine too.
Masdevallias and Draculas are fond about cold water (10°C).
All my medium to warm growing plants get water of greenhouse temperature (+-20°C). This I recommend also for Miltoniopsis.
I try and aim for water to be similar to the temps where the orchids are, but only very very roughly.
I keep bottles of rain water in the kitchen for the orchids in the house. I keep bottles of rain water in the greenhouse for the orchids in the greenhouse. Then if I'm using the tap in the winter I just mix in a little warm so it feels neither hot nor cold to my hand.
My masdies which like more cold are in the greenhouse at 5C over the winter so they get the water stored in there which is much colder than the stuff stored in my house.
I don't worry too much about what the plants growing conditions are and try and adjust the water accordingly, apart from my orchids that stay in the greenhouse over the winter (where I keep a min of 5C/40F), they naturally get the water kept in the greenhouse at a similar temp.
I think shock from cold water on a plant in a warm location can be a problem. I'm sure someone was talking about that a few years ago, that's why I just aim for having the water similar to the air.