Showering the Plants in High Heat

[carolyn137]

Originally Posted by QAGuy

Been 'showering' my plants for years. It was recommended to
me by Steve Goto, a well known heirloom commercial grower here
in SoCal. http://www.gotonursery.com/

In fact, he said that showering the plants can actually
cut down on fungus problems because the shower will wash off
airborne fungal spores.

I mulch heavily with grass clippings and I have NO fungal problems.

Caveat....this may not work as well in humid areas of the
country. Here in SoCal (just outside of Los Angeles), we
don't have a whole lot of humidity, so the plants dry quickly.

Humidity at the present time is 40%, which is
rather high for this area at this time of year. Usually, it's
down below the teens in the summer.

Still, I find it hard to believe that showering/watering plants prevents spores of tomato pathogens from attaching to the leaf surface. It isn't a casual association for there are specific receptors for these pathogenic spores.

And yes, I know Steve. When he first got more heavily involved in selling plants commercially he asked for my help in locating commercial amounts of seeds of varieties.

I live where water usually falls from the sky. Water falls from the sky where many tomato growers live. Whatever. Meaning, I don't lie abed nights listening to the rain fall and getting all upset about whether the plants will dry out so there won't be infections, etc., b'c there's not a darn thing I can do about it.

Rain fell on South America where tomatoes first appeared. Had they not lived we wouldn't have all the wonderful varieties we have today.

That's a good enough justification for me to ignore all the showering techniques and just go with the flow since right now I don't have the power to stop rain from falling from the sky.

[Noreaster]

OK, well.......this thread sure got interesting !

Our history with fungus (or whatever)we experienced for about 3 years was the rain or our own watering splashing up and destroying all bottom leaves. THAT was a nightmare.

For past 3-4 years, heavy use of straw along with improved watering techniques (like, duh, use of a straight 4 foot metal hose extension set on "flood" and water applied right on top of the straw in each bed) has pretty much eliminated our need to use Daconil very much. Generally we water twice a week to get that 1 1/2 inches of water goal.

But the burn-off of healthy buds has NOT gone bye-bye whenever a low to mid-90F streak comes along as it does each summer. That shading idea sounds good.....and think I'll look into it for future......hmm....very interesting. Last summer's heat streaks were VERY destructive to our plants and substantially reduced tomato production in late August, early September).

So, based on all responses combined........I'm going to continue this 2-3 LIGHT showerings per day approach to help prevent our plant buds from fully roasting like a turkey.

If disaster occurs......will definitely let this forum know !
Thanks to all for your responses !

[QAGuy]

Carolyn....water falling from the sky. I think I remember that
from when I used to live in Chicago.

We don't have that here in summer in SoCal. Last time it
rained (that is what you call water falling from the sky, isn't
it?) was in April!

Maybe I've been lucky. But if I do get an outbreak, I'll have
nobody to blame buy myself.

[oh2fly]

Those of you who water overhead like that in the heat, don't you have a lot of sunburned leaves? I sure do if I get any leaves wet in the heat of the day.

[montanamato]

I have literally cooked succulents by getting them wet in 100 degrees...I think the brief cooling they get is probably less beneficial and you are just adding stress to a plant in a stressed situation...
I will hose off my plants when it isn't above 95 as I like to flush the dirt and hoppers off the plant...I also have 12% humidity on average and virtually no fungal problems....
I think if I have a vast variety of plants , with varying degrees of blossoming going on , the actual loss during a heat spell is not catastrophic...Just my opinion, but tomatoes really are tough and usually get through most things mother nature can hand them...

Jeanne

[dcarch]

When you splash water on a leaf, several things will happen to the temperature of the leaf:

1. The temperature of the leaf will change up or down depending on the water temperature relative to the leaf's. Chances are the water temperature will get close to air temperature as the mist passes thru the air. In any case, both the leaf's and the water's temperature will quickly equal to the air temperature because of the very low mass and large surface area. Therefor the cooling effect of cold water on the leaf is minimal and short duration.

2. Once the water gets on the leaf, then depending on wind speed and humidity, the temperature will drop due to the "laten heat of vaporization". Some cooling effect can be gained because of this, again, the small quanity of water on the leaf will not give much more then a few minute's worth of cooling. If the air is moist and the water does not evaporate, than there is no cooling at all.

3. If the water makes the leaf darker, than the temperature of the leaf will actually rise somewhat from solar heat gain.

Wipe a wet towel on you skin, you will find out how quickly the cooling effect goes away.

Sunlight has over 400 BTUs per sq. ft. of heat. So shading is the most effective way to cool things down.

One way to achieve continued cooling effect is the use of an evaporative cooler. This too can only work when the air is not very humid.

dcarch

[feralcatfriend]

What about watering the plants in high heat, defined as over 90 degrees Fahrenheit?

I've been told to water in the morning or the very late afternoon, but not in the middle of a hot, sunny day, even if the plants are drooping, because the water would kill them.

So--does watering in the middle of a hot, sunny day kill tomato plants? If so, why? The shock of cold water on hot roots? Or what?

BTW, my tomatoes are in containers and I'm having good luck with using a long watering wand on spray and holding the head of the wand to the soil so there is little or no water splashed on the plants. I also prune the leaves on most of the plants up about a foot from the soil, so there are no leaves to get wet.

Cynthia

[Suze]

Originally Posted by feralcatfriend

So--does watering in the middle of a hot, sunny day kill tomato plants? If so, why? The shock of cold water on hot roots? Or what?

BTW, my tomatoes are in containers and I'm having good luck with using a long watering wand on spray and holding the head of the wand to the soil so there is little or no water splashed on the plants. I also prune the leaves on most of the plants up about a foot from the soil, so there are no leaves to get wet.

Welcome to Tomatoville. Watering container plants in the middle of the day is just fine.

[dcarch]

Originally Posted by feralcatfriend

What about watering the plants in high heat, defined as over 90 degrees Fahrenheit?
------------------Cynthia

One of the mistakes sometimes made in watering :

Garden water hose baking under the sun is like a solar collector. The water inside the hose can be burning hot.

Run the water for a little while first.

dcarch

[feralcatfriend]

Suze and dcarch,

Good to know! Thanks!

Cynthia

[QAGuy]

dccarch - kinda forgot about that bit. Here in SoCal, I automatically
do that whenever I water with a hose. Otherwise, it's almost like
pouring boiling water on the plants.

To address the 'water while it's hot and sunny' question, I have
to say that I seldom shower my plants under those conditions.

Oh yes, I have done it while the plants are very young and drooping,
but only because they are in desparate need of water! I generally
give them a shower in the evening when it's not that blazingly
hot.