LESS sun for full grown Tomato plants

[parah]

Full grown plants have only one job, set fruit.

I'm thinking about moving my full grown tomato plants to areas that only get sun until 1pm, because during the hottest part of summer days photosynthesis shuts down, right?

"Photosynthesis rapidly decreases above 94°F"
"The plant temperature at which tissue dies is around 115°F"
http://agdev.anr.udel.edu/weeklycrop...ag=heat-stress

If photosynthesis is shut down, then sunlight is only stressing the plant. Maybe that is OK for seedlings to toughen them up. But full grown plants with lush foliage don't need toughened up, they need to make fruit. Transpiration for cooling to survive afternoon sun uses energy, that energy could be better used to make tasty fruit to put in my pie hole.

I'm not ready to build an air conditioned greenhouse for my tomato plants, yet.
Is there and easy, practical way to know when the plant is using more energy to cool itself than it is gaining from Photosynthesis.

[Wi-sunflower]

I don't know the answer to your last question, but I do think you are on the right track as far as a more shaded area during the hottest part of the day. Other than moving the plants, you could also use shade cloth to help keep things less intense for them. I've seen simple structures similar to what we use for covering for warmth, used for shade material to keep things cooler. If built right they could also provide some air movement too. Chimney effect type of thing.

You might find some info on some of the threads by Texas or other SW growers. I know I've seen a few here in the past.

Carol

[parah]

I should have mentioned that I grow tomatoes in Raybo's containers with wheels so it is easy to push them around.

Surely some growers have compared plants that only get morning sun to plants that get full sun all day. Does it make a difference in fruit set during the hot summer days?

[parah]

Originally Posted by Wi-sunflower

I do think you are on the right track as far as a more shaded area during the hottest part of the day.
Carol

Thanks Carol, I am thinking about shade cloth for spring and fall days, but during the hottest summer days maybe ZERO sun is better when the temperature is above 96 degrees?

I think sombody mentioned that tomatoes can only use 25% of full sunlight, maybe I remembered that wrong.

[Worth1]

You need to think about one thing, you are not going to decrease the air temperature by moving them to the shade.
Air temperature is measured in the shade.
What you will decrease is radiant heat from direct sunlight.

I have and do grow tomato plants that get nothing but afternoon sun and only morning sun and dont see much if any difference one way or another.

I live about 1000 miles farther north of the equator than you do.


Worth

[Doug9345]

Originally Posted by parah

Thanks Carol, I am thinking about shade cloth for spring and fall days, but during the hottest summer days maybe ZERO sun is better when the temperature is above 96 degrees?

I think sombody mentioned that tomatoes can only use 25% of full sunlight, maybe I remembered that wrong.

Plants don't use the whole spectrum of sunlight and not all the sunlight is intercepted by leaves. I think if you take out full sunlight and go with the idea that plants can't use all the light that falls on them regardless of intensity you'll be closer in your thinking.

Also I don't believe that plants use energy from photosynthesis Water is transported up along the same lines as capillary action. It then evaporates out the stoma on the undersides of the leaves. This pulls more water up.

I don't know how hot you peak temperature get. I think it's worth a try to see what happens.

[parah]

Originally Posted by Worth1

I have and do grow tomato plants that get nothing but afternoon sun and only morning sun and dont see much if any difference one way or another.

I live about 1000 miles farther north of the equator than you do.
Worth

Thanks Worth, so I am probably wasting my time dragging containers around.

The tougher plants like Tarasenko6 can take the hot days without wilting, I was hoping that with a little help they could set fruit reliably. I know that is asking a lot from a big fruit variety. Blossom drop is discouraging.

[Worth1]

Originally Posted by parah

Thanks Worth, so I am probably wasting my time dragging containers around.

The tougher plants like Tarasenko6 can take the hot days without wilting, I was hoping that with a little help they could set fruit reliably. I know that is asking a lot from a big fruit variety. Blossom drop is discouraging.

If your plants are wilting it isn't because of the heat it is because they are in containers and cant get enough water.
No matter how much water you put in them there just aren't enough roots to take in enough.
What size are your containers?
Nothing less than 10 gallons would work well here and 40 would be better.
What my plants do in extreme heat is quit growing at all.
Then when the weather cools they start growing.
Here is how it is for me.
Plants growing and setting fruit.
Plants growing and blossoms drop.
Plants slow down growing and blossoms drop.
Plants stop growing and no blossoms.
Then this cycle reverses and goes the other way till they freeze.

I am going to try something this year you may consider.
As I mentioned earlier about the radiant heat from the sun.
What I am going to do is at a certain date start misting my plants several times a day when the temps get to the point the blossoms drop.

I have a controller that will automatically do this for me up to 12 times a day.
It can be pre-set to start this program on any date I choose up to as many dates I choose.
The amount of programs are infinite.

I will also put shade cloth over the plants to block some of the radiant heat from the sun.
My objective is to use the mist to cool the plants with a fan that automatically comes on to create a breeze on the wet plants to farther cool them.

Here is what the results will be.
It will work.
It wont work.
It will kill the plants.

I dont really care I just have to know.
For you I feel the shade cloth is the way to go it may help.

I dont grow in containers at all anymore.
What I can say is I grew a pretty good crop of cherry tomatoes in dappled shade one year in 5 gallon buckets.
This was about 20 years ago.

Worth

[Labradors2]

Worth wrote:

"If your plants are wilting it isn't because of the heat it is because they are in containers and cant get enough water.
No matter how much water you put in them there just aren't enough roots to take in enough."

Thanks for the explanation! This happened to one of my plants this winter. I watered and watered, and it hung in somehow. I think I was lucky that it wasn't THAT hot, and it survived.

Linda

[Worth1]

Originally Posted by Labradors2

Worth wrote:

"If your plants are wilting it isn't because of the heat it is because they are in containers and cant get enough water.
No matter how much water you put in them there just aren't enough roots to take in enough."

Thanks for the explanation! This happened to one of my plants this winter. I watered and watered, and it hung in somehow. I think I was lucky that it wasn't THAT hot, and it survived.

Linda

That's my take on it anyway.
I tried the container thing here in the driveway.
I honestly think the drain holes should have been plugged up.
You would soak the soil the plant would perk up and about 2 hours later they would wilt again and the soil would be dry.
Temps in the 90's and 100's.
What a waste of time.

I grow my elephant ears in 40 gallon feed containers filled with mud and muck and rotted leaves with no drain holes and full of water all of the time.
They are sunk in the ground.
Works great.
Worth

[Labradors2]

I bought some big plastic saucers and bottom watered, filling the saucer to the brim. The plant would guzzle all the water and I'd water again, yet still the top of the soil would be bone dry. I watered from the top even though I hate to do that because of the wretched fungus gnats and the plant seemed happier, but it wasn't a good test because the weather changed and I was unable to put the plant back outside for ages. I thought it was the potting mix causing the problems, but it could well be that the plants roots were not large enough to support the plant.


I don't like to put plants in containers without drainage holes, but if Elephant ears like growing in water, they may not care!

Linda

Originally Posted by Worth1

That's my take on it anyway.
I tried the container thing here in the driveway.
I honestly think the drain holes should have been plugged up.
You would soak the soil the plant would perk up and about 2 hours later they would wilt again and the soil would be dry.
Temps in the 90's and 100's.
What a waste of time.

I grow my elephant ears in 40 gallon feed containers filled with mud and muck and rotted leaves with no drain holes and full of water all of the time.
They are sunk in the ground.
Works great.
Worth

[Dewayne mater]

I absolutely agree that full sun in the hottest part of the day in hot places is a negative for plant health. I have some in ground plants and some Raybo earthtainer plants and use a variety of means to avoid direct sun in the hotter part of the growing season (begins May 15 to June 1).

In ground - can't move them, so I use 50% shade cloth starting in the May 15 to Jun 1 time frame, depending on if the heat is regularly topping 94. These plants have southern exposure and get tons of light all day. I have noticed that when I walk under the shade cloth vs. standing in the sun, the temp feels much much hotter to me, like 15 degrees hotter in the direct sun. I doubt the air temp is actually different, but, the effect of full sun makes it more uncomfortable for humans, it is probably somewhat that way for plants.

Tainers - I start them in a full sun area on concrete for the early part of the year, now until approximately May 15. At that point, I'm lucky to have a space that is directly adjacent to the driveway that is full sun, to a grassy patch that gets full sun until 3 pm. and then is fully shaded by the house. About May 15 I move the tainers 1 time, very carefully to the partly shaded area. In the full sun area, before I moved them to the part shaded area, the plants went from having massive problems with BER, and being massively stressed in the full sun area in the heat, to now having zero BER, no significant stressors (beyond the usual battles with disease and insects) and having a productive cycle that lasts 4 to 6 weeks longer than before I moved them. In fact, I now regularly have tainer plants that make it through the summer and produce again in the fall, something that never happened before employing this strategy.

This is of course just anecdotal, but, the conclusion I draw is that for me, in N. Tx where it gets hot May and stays that way until October, getting shade for the plants in the hottest part of the day is essential and doing so results in far more production than if I don't.

Good luck.

Dewayne Mater.

[Worth1]

I know this sounds like I am talking out of both sides of my mouth but there are a lot of things to think about as far as radiant heat and shade heat.

You are about 1000 miles farther south than I am.
What is the sun rise and how many days of sunlight do you get?
I would think around 13 hours or so right.

If you put the plants in an area that gets full sun till 1:00PM and dappled shade from then on I can see this might help.

Just a thought.

Worth

[carolyn137]

Originally Posted by Doug9345

Plants don't use the whole spectrum of sunlight and not all the sunlight is intercepted by leaves. I think if you take out full sunlight and go with the idea that plants can't use all the light that falls on them regardless of intensity you'll be closer in your thinking.

Also I don't believe that plants use energy from photosynthesis Water is transported up along the same lines as capillary action. It then evaporates out the stoma on the undersides of the leaves. This pulls more water up.

I don't know how hot you peak temperature get. I think it's worth a try to see what happens.

Yes, photosynthesis does make energy compounds the most important being ATP which is a catalyst for enzymes involved in plant growth.

I think this link is a good one:

http://biology.clc.uc.edu/courses/bio104/photosyn.htm

And it also has some hints about growing in hot conditions as well and also describes the light and dark parts of the cycle.

Years ago when my plants got too tall for me too quickly my farmer friend Charlie told me to take off all foliage and just leave a tuft of foliage at the top and it worked as in slowing down plant growth. Charlie didn't know about what happens with photosynthesis, but he did know that taking off most of the leaves slowed down growth.

Carolyn

[Doug9345]

But I don't believe that energy is used to transport water in a plant.