There is some info about it in one of the FAQs here.

"Hormone sprays, such as "Blossom Set", may prevent some blossom drop due to LOW temperatures. However, the resulting fruit are often misshapen. But studies prove that hormone sprays do not prevent blossom drop due to HIGH temperatures."

See: http://faq.gardenweb.com/discussions/2766768/why-are-the-blooms-on-my-tomato-plant-dying-and-falling-off

In my personal experience testing it many years ago I found those statements to be quite accurate - many heavily fasciated fruit, an uncommon amount of cat facing, and no noticeable increase in overall production. Given the way tomato pollen is so sensitive to ambient air temps I found it difficult to understand how a hormone spray could possibly make inert pollen suddenly viable. Perhaps that is why so many gardeners scoff at it, Thus my own test.

But how a hormone that promotes cell division in plant cells can somehow trigger "more blossoms" on a plant escapes me. More cells and faster division of those cells does not equate to more blossoms.

But why not try some for yourself and see if it works for you.

Dave

"But how a hormone that promotes cell division in plant cells can somehow trigger "more blossoms" on a plant escapes me."

digdirt, I think I can point you in the direction of those slick marketeers, but it is a artsy area, as this is not a scientific statement, but rather a marketing claim. Let's look at label and do a little emasculation of our own:

"BONIDE TOMATO & BLOSSOM SET SPRAY is a ready-to-use natural plant hormone product that provides Biological Grow Power to promote blossom set and fruit development. Used as directed, Tomato & Blossom Set Spray will promote flowering, increase blossom set and increase fruit yield."

First observation: There are two separate claim statements that seem to repeat themselves somewhat (red flag, lame strategy to comply with FTC and misrepresent to consumers by having us assume what we want to hear). Clearly the hormone(s) used are claimed to promote blossom set and fruit development. That is the only claim on the cytokinins, but you, like 100% of everyone else who reads assumed more because of the next claim is purposely crafted to trick your mind with smoke and mirrors. The second claim refers to the spray, not the cytokinins, and here you are thinking, well, gee, that's all that's in the product obviously.

However this is classic advertising wording to obscure that the formula has some other ingredients that actually do the "promote flowering" part stated in claim #2. Notice in claim #1 they call it a "hormone product" They can put whatever they want in there (it is now a product, it's a sleight of hand) and it can have the most minimal effect and the claim is still true. So all they have to do is put a tiny amount of nutrients in there probably food grade and GRAS not requiring labeling, and presto, they are promoting flowering. That is a valid claim for any fertilizer including a few ppm of vitamins and minerals. Mystery solved ;)

PS, it's a good product, and as digdirt says it works in cool conditions. I have also tried it, but it is too inconvenient for my taste, because I usually want my tomatoes to have seeds in them. I find the seedy, tasty varieties I like just don't taste as good without them, and the product works but not really increasing seed count. I may be wrong, but that was my opinion. Possibly my error is that in those conditions the tomatoes taste crappy anyway. So it isn't something that I'm excited about anymore. But I agree you should give it a try.

PC

hormone product that provides Biological Grow Power to promote blossom set
&&&&&&&&&&&&

Most of us are concerned with pollination and fruit set of the existing blossom. Usually most tomato plants produce adequate flowers. So the problem is pollination NOT THE LACK OF BLOSSOM SET.
JMO

Sey

Thank you everyone! I actually have 3 different varieties that produce very few flowers: Persimmon, Bulgarian triumph and Red Truffle. They are tall and good looking plants and they have maybe 3 tomatoes set on each, but it is not enough for me. OK, I'll buy this product and I'll do my little garden experiment. I've bought liquid bloom fertilizer which i'll use on a couple of tomatoes as a foliar fertilizer. And I'll use Bonide Blossom set on the other two plants, the others will be my control group. Of cause they are all different varieties, but I'll notice the trend in flowering and fruiting in general if there will be an effect from these products.

"I actually have 3 different varieties that produce very few flowers"

Good luck! I hope you can boost your yield and we'll take it however we can get it :-) I never have enough flowers even when the plants are going through their version of "Kona Snow". More blossoms = more tomatoes, when doing your best, all else being equal, it's just a numbers' game :-).

You can just spray fresh coconut milk on your blooms if you want to have more fun. I doubt the cytokinins in these products are extracted from tomato thought it's a possibility. Coconut milk (a.k.a coconut water) contains a great deal of them with other nutrients that will "promote blossom formation" as well.

<digdirt, I think I can point you in the direction of those slick
marketeers, but it is a artsy area, as this is not a scientific
statement, but rather a marketing claim. Let's look at label and do a
little emasculation of our own:>

Yeah I know PC. Was being a bit facetious there. ;-)

antmary - there are many other reasons, and far more likely ones, as to why your plants may not have many blooms on them. Excess nitrogen is one of the most common reasons, ambient air temps another, inconsistent soil moisture levels another, etc. Basically anything that stresses a plant causes a reduction in blooms.

Dave

Pupilla, it is an amazing tomato. Is its flowering really caused by the application of coconut milk? Amazing.

Dave, you are pragmatic as ever but it really helps in most cases. My tomatoes did have some boost with chicken manure, but it did not explained why some varieties growing side by side have so much difference in blossom numbers.

Anyway I decided against using Bonide blossom set. As a part of my job I often use chemical reagents. I am thinking how stable is the kinetin in this bottle? It is well known that almost all organic substances degrade quickly at the room temperature. I looked at the Sigma-Aldrich website, which sells chemicals. It sells kinetin as a concentrated stock solution and it ships it at -20 C and recommends to store it at -20 C. So that means it is not stable at the higher temperatures for the long time. The Bonide bottles sat on the counter for the unknown time, and the temperature in the nursery was 86 F or higher when I have been there.

Actually I saw a small vial of kinetin 10 g powder sold only for 10$ plus shipping on Amazon. It should be gallons and gallons of diluted solution, but it is too much trouble for the couple of tomato plants. So I'll stick with the foliar fertilizer for the blossom set instead. It is not really big trouble since I have to spray fungicides every week now.

I used it twice, in a series of yearly tomato growing. The spray definitely works. I’ve experienced so many more tomatoes, not misshapen at all, (as described in one of comments above, )and they all have plenty of seeds. I didn’t notice the tomatoes having less seeds at all.

I also live in a very hot place and can grow tomatoes when others don’t even try , because of the spray.

I will never go another growing season without using this!

this year I’m using it on my whole garden. I will never not use this. It’s amazing!

Is it ok to still spray on the flowers early in the morning, if/ when heat reaches the 90’s in the afternoon?

i appreciate any insight, new raised gardener here in Texas. Thanks!

I have not used the Bonide brand, but I have used Blossom set. It does not do anything for blossoms but it does make early blossoms set in cool weather ( upper thirties- low 40's) The tomatoes that respond to Blossom Set will be seedless. Back in my younger days in a zone 6 climate, we competed to get the first tomato. Blossom set gave up a little jump when using plants that were blossoming when transplanted.

Does anyone know if rain affects the potency of tomato blossom set on the flower?