I water all my container citrus over (50+ varieties) throughout the winter using 70 - 75F (21 - 26C) warm water. The warm water is beneficial to citrus. My tree's have 0 percent WLD. - Millet (387 ABO-)

you did not mentioned what was the air temperature at the time of watering , if it is 75F than we are talking about different situations

Mine are at 30-35F at this time....so it is not the same ,I guess!

My greenhouse night time temperatures during the winter months are between 50-55F (10-13C). The day time temperatures are determined by the amount of sunshine during the day, anywhere between 60 to 80F (15-26C). However, I would not think 70F (21C) irrigation water should bother a citrus tree even if the air temperature was 35F (1.6C). - Millet (387 ABO-)

I agree with you on that , that the warm water will do some good to the roots ...but....when the soil is at 35 and I pour warm water on the soil will have the water temp but only for a while , after it cools down to 35 and I will have a cold and above all a wet soil too dangerous for the roots.

Am I right ? Cold and wet.

Daniel

Daniel, my honest answer to your question (cold & wet roots), is that I cannot say for absolutely sure, as I have never had that situation. I would just say that under normal conditions, the amount of water applied does not cause a problem, it is the lack of root zone oxygen that causes root rot and other root problems. In potting mixes that are compact, poor draining, and etc. over watering fills all the medium's pores driving out the oxygen. However, in a free draining medium, with at least 25% air porosity, such as CHC and bark potting mixes, the amount of water should not cause a problem, because the root zone oxygen is immediately replaced. - Millet (386 ABO-)

Ok , I understand.

And another thing , why at low temps water does not make the same damage as if in warmer conditions

Those in the house are doing little worse compare to those on the porch at 40F.

Is it because of the stand-by state of the tree ?