Blossom set in the heat.

[Red Dirt Farmer]

Blossom set hormones such as cytokynin are normally used in colder springs when the tomatoes or peppers have a drop problem due to cold nights.
Here in central Oklahoma, we are on our 19th day over 100 degrees. I planted late this year so my indys are only about 3 to 4-feet high so far but in good shape. No fruit set because of the high temps, so I spayed the blossoms with fruit set hormone.
My question is this: Will this work in the heat as well as cool temps?

[carolyn137]

Originally Posted by Red Dirt Farmer

Blossom set hormones such as cytokynin are normally used in colder springs when the tomatoes or peppers have a drop problem due to cold nights.
Here in central Oklahoma, we are on our 19th day over 100 degrees. I planted late this year so my indys are only about 3 to 4-feet high so far but in good shape. No fruit set because of the high temps, so I spayed the blossoms with fruit set hormone.
My question is this: Will this work in the heat as well as cool temps?

According to what I know from feedback from others, there's little chance it will do anything.

Blossom set was devised to be used in cool spring conditions b'c the temps are too cold for pollenization to occur, as you noted above, and what it does is to side track normal pollenization and induce parthenocarpy.

In high sustained heat and/or humidity the pollen is actually denatured, destroyed, for high heat, and clumped with high humidity.

Folks use the blossom Set product just for initial fruit set and when the temps go up then they no longer need to use it.

YOu can go the route some do, but not necessarily in a high heat situation, and shake the plants a couple of times a day, or whack them with a broom, or use a vibrating toothbrush, but none of those are going to work if the pollen is non-viable due to high heat.

Hope that helps, at least somewhat.

[Red Dirt Farmer]

Thanks Carolyn, I was afraid of that. I have been shaking but the only variety to set fruit so far is a Sioux. Of course, I will report back with results, neg or pos.

Ken

[b54red]

Try heavily watering the plants. I have found it very helpful in getting some decent fruit set in the high heat and humidity. It seems that during these hot times the plants need far more water than in the spring or fall. I think when they are losing so much moisture during the high temps the stress causes far more blossoms to fall when they are under watered.

Some varieties also seem to set more fruit during high temps than others. Indian Stripe, Spudakee, Andrew Raharts Jumbo Red, Mule Team, Red Barn, Black Krim, NAR, BTDP, and Gary O' Sena have all set fairly good even in the hottest weather when given enough water and a little extra fertilizer.

What have you got to lose by trying it on some of your plants. I just left my soaker hoses running for over 12 hours on the plants I set out in May and June. Then last night got about a half inch of rain. If it doesn't rain again within 3 days I will do it again along with giving them all a dose of MG.

[luke]

If it works, please post in here for all of us to see. My plants put on blooms right about the time that we had a stretch of 100 degree and plus days, and I have hardly any tomatoes.

[carolyn137]

Some varieties also seem to set more fruit during high temps than others. Indian Stripe, Spudakee, Andrew Raharts Jumbo Red, Mule Team, Red Barn, Black Krim, NAR, BTDP, and Gary O' Sena have all set fairly good even in the hottest weather when given enough water and a little extra fertilizer.

*****

Bill, that does surprise me quite a bit, as in you can't cool plants down with water, watering them as I see it would just add to pollen clumping which is the equivalent of high sustained humidity.

And high sustained temps can just plain destroy the pollen by denaturation.

I'm glad that adding more water and fertilizer help with fruit set for you but still, I have to wonder.

BTW, how come adding more fertilizer which can also be a stress by making the plants grow too rapidly?

And the usual disclaimer so that tomato growers don't sue other tomato growers...... your mileage may vary.

The normal blossom cycle is about 2-3 weeks and many folks find that even small temp changes can help if blossom drop has been a problem.

[Worth1]

Originally Posted by b54red

Some varieties also seem to set more fruit during high temps than others. Indian Stripe, Spudakee, Andrew Raharts Jumbo Red, Mule Team, Red Barn, Black Krim, NAR, BTDP, and Gary O' Sena have all set fairly good even in the hottest weather when given enough water and a little extra fertilizer.

Can you please tell us which of these varieties set fruit in 100+ temperatures with the heavy watering.
If they didn't set fruit in that high of a temperature (with heavy watering) then how hot was it.


Worth

[Keiththibodeaux]

Originally Posted by carolyn137

,,,as in you can't cool plants down with water, watering them,,,.

While plants don't feel the effects of humidity as humans do, or at least I assume they don't, is it possible the evaporivative effect of the water cools the air around the plant. I am thinking of the misting systems being sold now claiming to reduce temps. Just a thought.

[piegirl]

I know you are mainly mentioning heirlooms, but one hybrid that has done well for me if Jet Star. We have had near 100 degrees and suffocating humidity but still they set. JD's Special C-Tex is also setting heavily. Piegirl

[creister]

To the original poster, save your money, the fruit set spray does not work in high temps. You'd be better off buying some beer and giving your plants a drink to cool them off. If you live in an area of high heat, plant out earlier than you should, be prepared to cover plants a few nights, give them a shake or two every day, and you will get tomatoes.

[creister]

Another thing, without night time cooling (below 70) plants stress from high heat. I am growing Jet Star, and nada for fruit set since mid May.

[Aphid]

any pollen can go sterile above consistent 98f... I don't see how a spray will fix that

[Pants]

Originally Posted by carolyn137

Bill, that does surprise me quite a bit, as in you can't cool plants down with water, watering them as I see it would just add to pollen clumping which is the equivalent of high sustained humidity.

And high sustained temps can just plain destroy the pollen by denaturation.

I'm glad that adding more water and fertilizer help with fruit set for you but still, I have to wonder.

You're right that water won't help with the sterilization of the pollen (which I've always assumed was the biggest issue with high heat), but it is important to water in high heat. Plants need both water and carbon dioxide to perform photosynthesis. The water of course comes from the roots, but the carbon dioxide comes in via pores in the leaves and stems called stomata. The trouble is that when these pores are open not only does the plant bring CO2 in, but it can lose water vapor. When the temperature is very high most plants will need to keep those stomata closed to avoid losing water. This effectively shuts off photosynthesis (though some plants store CO2 during the evening to use during the day). If you keep the plants well watered they can keep their stomata open during the day and thus keep photosynthesizing along.

BTW question, you've been using the term denature to describe the destruction of pollen. This to me implies that the mature pollen is being denatured and thus destroyed by heat. I had understood the issue to be that meiosis does not work at high heat and therefore the problem was fertile pollen can not form at all. The main difference I see between these causes is that if it is denaturation of mature pollen then the heat will destroy flowers that have already made pollen, but the closed ones would be safe. While my understanding would be pretty much the opposite, any flowers that have already formed pollen would be safe and it would be the developing flowers that would be damaged. Do you know for sure which case it is?

[b54red]

Carolyn, I don't know why it works but it does. I am just assuming that the stress from high heat causes the blossoms to drop and the added water helps reduce plant stress. I found this trick by accident last year in late July when I thought all of my plants in one of my beds were finished producing and I didn't feel like pulling them out right then because I didn't need the space for my fall tomatoes. So I pruned them heavily and gave them a good dose of MG and turned on my soaker hose. I forgot to turn it off and it ran for nearly two days and made a huge mess. It was nearly a week before I could get near the plants because of the mud. When I did they were loaded with blooms and many had set fruit despite temps above 100 degrees. As soon as my fall tomatoes got to the blooming stage I started heavily watering them and they started setting in the 100 plus weather. I did the same thing this year since we had unusually high heat where it actually got over 100 in May and we have had temps consistently from the mid 90s to above 100 since that time with few nights below the mid 70s. Once the plants start producing I cut back on the watering so the flavor will be better. I am still setting out plants and will continue to do so til mid August. I do not water the new plants heavily but instead plant them deep in moist ground and then not water them until they start suffering; but as soon as they start blooming I start very heavy watering.

luke, I will try to get out and take some pictures this morning of some of the plants that were set out late and have not seen any cool weather. I have been planting through the summer with staggered plantings for several years and the heavy watering when they start blooming has boosted my production significantly. I used to think that tomatoes could not be grown in the heat of mid and late summer. It is not easy nor do the plants or fruit get as large but it is definitely doable. I only started the staggered planting because of my huge losses from fusarium wilt and just continued right into the fall once I saw some success with this method. I really like having fresh tomatoes all season and not just a huge crop for a month or so which I was getting with my previous method of putting out all my plants the same day in early spring.

[carolyn137]

BTW question, you've been using the term denature to describe the destruction of pollen. This to me implies that the mature pollen is being denatured and thus destroyed by heat. I had understood the issue to be that meiosis does not work at high heat and therefore the problem was fertile pollen can not form at all. The main difference I see between these causes is that if it is denaturation of mature pollen then the heat will destroy flowers that have already made pollen, but the closed ones would be safe. While my understanding would be pretty much the opposite, any flowers that have already formed pollen would be safe and it would be the developing flowers that would be damaged. Do you know for sure

*****

I've used two words with regard to pollen, one is denatured, aka destroyed, and the other is clumped pollen.

Pollen is protein in nature so high sustained temps can denature it by breaking some of the bonds that comprise the structure thus rendering it useless.

It doesn't matter if the blossoms are open or not and indeed most self pollenization takes place before the blossoms are fully open.

The formation of pollem by meiosis takes place before the viable pollen is even present in the closed blossoms so I don't know how to connect the two since I would assume that only fully formed viable pollen would be denatured by high sustained heat. And that leads to blossom drop. Andything that impedes self pollenization or even cross pollenation would do the same.

And not all pollen is created equal in terms of apparently identical structure b'c I remember talking with a hybridizer from Petoseed who was working on clumped pollen in FL and he spoke to that issue.

The individualgrains in Clumped pollen are viable but b'c it's clumped it's much less effective and that was my point about getting water on the open blossoms. For sure plants need water and yes, for photosythesis as well, a subject I taught before I retired amongst many other subjects.

Insects that work the blossoms are not there for nectar b'c tomato blossoms don't have any nectar, they're there to collect the pollen as a protein source.

Above you said that plants store CO2, and for sure my memory isn't perfect, b'c what I remember is that there are two cycles of photosythensis, a light and dark cycle and that compounds put together in the light cycle are stored and then distributed as individual building blocks into macro compounds during the dark cycle. Not just CO2.