Why in summer-time is it wrong to water in the mid-day heat?

Have a look at my blog on watering for beginners, but added to that, the reason you wait, preferably til evening or early morning, is that there is much less risk of splashing the leaves - if that happened in hot sun, the leaves would burn and scorch. Also, the water gets a chance to be absorbed by the plants before it gets baked off by the sun.

Hi Bamboo, Yes, I always take great care to water with precision, not letting a drop get on the foliage of anything. I am also aware that roots of plants are generally what I think is correctly called 'hydrotropic'. Have I got the right term? ... By which I mean, they're growing/going in search of moisture, developing in such a way. Thus, it is better to occasionally deep water that to regularly give small amounts, so that a good and deep root system develops. Half of my garden is in fact in pots, containers and baskets. I tend to water at all times of day, morning, mid-day heat, and in the cool of evening. I'm still a bit confused,- still don't really understand this thing about "watering so that it gets to be absorbed before it can be baked off". (I've been and read your blog). Best wishes.

Evaporation, Jonathan. If you water in hot sun, the water evaporates before reaching the bottom of the pot or roots in soil. That, combined with the possibility of burning the leaves is why you should water early or late. If you water in the evening, the plants have the chance to absorb all the water to sustain them through the next days heat.

I do carefully water my pots sometimes during the day if they look in particular need though.

If ind that if a plants needs watering, whatever time of day it is, i give it some. NOt on the leaves as the roots need it, but then if the plants it hosed down, it keeps it cooler and slow the evaporation of water from it.
Im not convinced with scorch. If its hot and sunny and then it rains, then sun comes out, nature wouldnt invent the idea of scorching leaves.

Thanks everyone. I think I'll conclude that I'm doing watering in an OK way, in the mid-day heat as well as in morning and evening cool. Just as long as I A) keep water from splashing on leaves, and B) make sure I water pots deeply, all the way to the bottom of them. Like Nickky says, it does seem a bit illogical to have to avoid getting water on leaves, seeing as nature does it anyway, just whenever there is sunshine and rain showers. But I have a feeling that there is variability and that some plants may be 'undamageable' in that respect, but other plants a little more vulnerable.

Touching faith in the essential "goodness" of nature there, Nickyt08! Oh, if only it were true....

true but likely...