fill watering can ... the day before ...

use the next day ...

and forget about worrying about it ...

i keep a bleached out gal milk jug ready.. at all times.. so i dont have to wait one day ...

i would NEVER use heated water from the tap ... as there is no way of knowing its heat level ...

its a variable... and i like to reduce variables... not increase them.. room temp .... is room temp ...

on some level.. you are treating your plants like a baby ... thinking it needs it bottle warmed ... its not a babe ... and room temp.. is room temp ...

have fun

ken

I've been on a mission for years, to find anyone who can offer anything definitive on why you shouldn't water with cold water directly from the tap. I've asked at least 50 people with horticulture-related degrees and none could think of any reason it might be detrimental. On the flip side of the coin, we know that watering with water warmer than 90* or so carries the potential to impact root function or even kill roots if warm enough. Water that feels warm to the touch will be close to 100* or warmer (warmer than body temp, at any rate), so, warmer than the plant would prefer.

In physics, the second law of thermodynamics says that heat flows naturally from a material at a higher temperature to material at a lower temperature, so from the warm water to the cooler (room temp) soil. The increase in warmth of the soil corresponds to an equal degree of cooling of the water as it passes through the soil, so it feels much cooler when it exits the drain hole. Simply said, the water leaves a large portion of its heat in the soil as it passes through, so it feels colder as it exits the pot.

Al

This post was edited by tapla on Wed, Oct 15, 14 at 18:01

This is a bit like a "How long is a piece of string" type of question. You'd need to be more specific with what temperatures you're talking about.

One of my colleagues, who has 35 years' experience of watering plants every day, swears blind that warm, bordering on hot, water has never harmed one of his plants.

Equally I'm not aware of cold water hurting a plant that is in a sufficiently warm area.

But given a mixer tap I go slightly luke warm out of habit!

Maybe taking a hint from nature - rain water is generally cold - not freezing, just cold. Just thinking out loud.