Hi wild forager - many past discussions on it if you want to review them but the general consensus is that it is a waste of time and money. Per the FAQ here on it: "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."

So if blossom drop is the problem you are having, the FAQ on it (linked at the top of the page) offers several more effective prevention techniques.

Dave

Not sure where you got the consensus info from Dave but I've used the Blossom set spray in both aerosol and pump mist and it not only has proven to set fruit in cooler weather in the absence of bees but the resulting fruits have been beautiful on the outside and very desirable eating with fewer inside seeds. I wouldn't be without it.

A can/bottle size may vary but one 6 oz. container can treat hundreds of blossom clusters. If I were to guess I'd say you can treat 500 clusters with that amount. The objective when treating is not to wet the flowers but just lightly mist them once. I can usually treat clusters from 200 plants in 15 minutes and repeat for opening blossoms every 4-5 days in the early season. Costs range between $4 and $6 for a 6 oz. container that ensures $400-$600 in early tomato crop.

absence of bees ???

Since tomatoes are self fertilizing, absence of bees has
little to do with fertilizing your tomatoes.

You're better off shaking the blossoms.

Not sure where you got the consensus info from Dave but I've used the Blossom set spray in both aerosol and pump mist and it not only has proven to set fruit in cooler weather in the absence of bees but the resulting fruits have been beautiful on the outside and very desirable eating with fewer inside seeds. I wouldn't be without it.
*****

I'm glad your experience has been a good one, but for many others it hasn't been a positive experience.

The reason being that the plant homones that are in Blossom Set, such as indole acetic acid, induce parthenocarpy, which means the development of fruits in the absence of fertilization by pollen b/c the temps are too low for that to happen normally, and I know you know that that's why there's so few seeds in the fruits.

IN addition, because fruit development is abnormal it is possible to get a mushy interior as well as misshapen fruits.

Will this happen for everyone? No, but it does happen for some folks.

All of these abnormalities can be found by Googling Blossom Set.

I know that you're a market gardener and thus feel that the earliest fruits you can market the higher the prices you can demand, but for most of us home growers, I'd rather let nature take it's course without intervention.

From what I've read in the past it seems to be used most in areas like the PNW where it stays coolish for long stretches of time in the early Spring. And that's the same reason why Dr. Jim Baggett at Oregon State University developed parthenocarpic varieties such as Oregon Spring for the PNW.

Carolyn

Not sure where you got the consensus info from Dave...

From a search here and a quick review of the many past discussions about it. :)

I too am glad it seems to work up north for you but my personal experience with it here in the south only confirmed what the FAQ says - fruit that has to be pitched.

Dave