I've heard the first one before, and the theory is that the water droplets act like lots of little magnifying glasses and concentrate the sun's rays. That doesn't happen, but it's usually best to water at night or in the morning so that you lose less to evaporation.

I'm not sure I follow what's going on in the second one. I'd never take my plants into the shower to water them, anyway. It seems kind of an odd way to water.

Yes, they are both true. As bp says watering in the direct sun or in the hottest part of the day often leads to sunscald of the leaves. Spots appear where the sun/water combo heat has killed the cells of the leaf.

The second one is true not so much because of the droplet acceleration tho that can easily cause damage but because any and all overhead watering of anything except grass should be avoided. You can't control the rain but you can control how you water and overhead watering is problematic.

All plants benefit more from soil level watering than hose or sprinkler watering. Overhead watering not only wastes water to evaporation but it wets the leaves, causes burns discussed above, encourage soil splashing onto the leaves and leads to fungal and bacterial diseases.

Mama and Daddy are right - as per usual. ;)

Dave

Dave--you misread what I wrote. I said that it does not lead to scalding, but it's inefficient because more is lost to evaporation.

Oops! sorry bp. I sure did misread it. So can I disagree with you on that point?

It's just a

littleone. ;)

Dave

one neighbor told me never to water at night because it could mold. well get mildew on it. is that true??

"one neighbor told me never to water at night because it could mold. well get mildew on it. is that true??"

Sometimes. It's not a concern for me because it's so dry here, but in more humid areas, watering at night means that the lawn is damp all night long and that can lead to various fungal issues. If that's the case for you, your best time to water is in the early morning. That way, you don't lose water to evaporation, but it's not sitting there all night leading to fungus.

watering at night makes for more slug problems....

as already said, it is much better to water the soil not the leaves, youre just encouraging fungal diseases and wasting water that way. put the shower head under the plant when you water :)

"Don't go an' water 'em plants when that there sun shines out, or they'll BURN"

NOT TRUE.

If you don't believe me, go out the next time the sun shines after it has rained, and see for yourself what isn't happening :-).

"Don't go an' water 'em plants when that there sun shines out, or they'll BURN". An old myth disproved by research. Water droplets will not act as a magnifying glass, maybe a prism and maybe make a rainbow in your garden but they will not "burn" your plants.
"Don't go an' water 'em plants with that there shower spigot, as this action is likely to rupture the leaves as each droplet encounters a fair bit of acceleration due to gravity." Maybe, possibly if you were to hold that nozzle up against the plants leaf, but if your are a foot or more fromt he plant the velocity of the water would fall off enough so no damage to the plant would result, unless you sprayed a straight stream directly toward the plant, something I doubt anyone with a modicum of sense would do.
Now "Do not water during the heat of the day" and "Do not water during the night" pretty much limits the time you can and since, if you believe these restrictions, you cannot water in the evening either, because you cannot let your plants be wet at night, that pretty much leaves early morning as the only time you could water, so unless you have an automatic sprinkling system you need to start watering around 5:oo am.
I have watered during the heat of the day for most all of the time I have had a garden, or worked in gardens (starting in the 1950's) and have not had any problem listed by those that are adament about not doing that and since that watering cools the plants during the heat of the day they do not wilt or show signs of heat stress which is better for the plants than having them get stressed from the heat.

Water droplets on foliage are the wrong shape to act like a prism, focusing light so that the tissue will burn. It's one of the many horticultural myths, this one easily dispelled by simple physics.

As far as the other thing....have you ever noticed the terrible devasation and destruction in your garden after a heavy rain storm? NOT!

Whew, we just went through a heavy downpour and of course I went out to see the damage. None. The sun's peeking out now and I'm sure the garden would be destroyed if that myth were true. There goes last night's Daconil though.

It doesn't rain at all here from about May to October (except the lone July rainstorm), so it's a good idea here to water from above to wash off the leaves -- mostly dust -- so the plants can respire better.

And because heat waves occur here every month or two, so plants are not adapted to them, it's a good idea to give them a sprinkle in the middle of the day. I've seen hydrangea leaves burn in the shade from high temperatures! So if I'm outside anyway, I sprinkle the plants a little in the middle of the day to cool them down during a big heat wave.

I know it's best to water in the morning, but my schedule does not always allow it, and at the community garden it's often counterproductive to water in the mornings because the water pressure is so low then. It's more efficient to water in the afternoon or evening because that's when I can be there!

I follow the lead of Me Mither (Ma Nature) and water the garden any old time I can. In the heat of the day, or late at night or anytime in between. And I try not to hit tender leaves with high-pressure fire hoses. Ma Nature dprays her gardens with drops of water at a speed of about 6.5 m/sec. Hard to measure, but a rough rule of thumb might be, if you're not tearing your plants to ribbons, the terminal velocity of the droplets is probably ok.

In 35 years of gardening, I've never had a plant "burn up" by watering in the heat of the day or get torn to tatters by the spray of the hose. (Maybe I've just been lucky all those years?)

Wayne

i try not to water no later than when the sun is about( if you can imagine it in a clock's face.) at, (if i'm facing south) 2 o'clock. i don't water between 12 and 4. because i'm afraid of stressing my seedlings. my regular plants i'm not to worried about. they recover really well from anything, even talla, (my 6 yr old daughter) who sings to them and pulls their leaves off for her fairies, LOL ~Medo

Old wives tale? Naw, in this case it's an old man's tale. Old man who has seen way too much leaf damage, tears and holes, sunscorch and foliar and fungal disease from mid-day, overhead watering. Some plants may tolerate it better than others - your choice of course - but it's not worth the risks to me.

Tomatoes for example won't tolerate it, most monocots won't because of the way the veins run in the leaves - there are picture posts daily on the Tomatoes forum showing the damage done. And the damage doesn't show up right away either. Sometimes days later you find yourself wondering what happened to the leaves on your plants. Google "sun scorch" and "proper watering techniques" for more info if you wish.

Rain you can't control - clouds are above the ground so the laws of gravity kicks in. But that doesn't mean you have to water that way. Still we're all gonna do what we're gonna do regardless of any evidence to the contrary, but if you ever have problems with your plants, changing the way you water is something you might want to consider. ;)

Dave

I thought tomatoes were dicots?

Good point habitatgardener - it depends on where you live and what you do all day. Here I find that not watering between 11 and 4, nor after about 6 pm, gives me plenty of time. I avoid watering in the heat of the day because so much of it evaporates, or later in the evening, to make it harder for the slugs to travel, and to let the foliage dry before night, although I try to water the soil not the foliage (or 'foilage' as some Nova Scotians like to spell it - I've even seen it written that way on a flower shop sign, which conjures up a plant putting out metallic greenery in order to reject rain).

Tomatoes are dicots, alfie. Sorry, didn't mean it to read otherwise but I can see how it could be interpreted that way. ;)

Dave