From what I've heard heat bakes the pollen and renders it useless. Has it been hot and humid?

Mine are bursting into flames on the vine so keep your head up. :D

Usually, Flowers fail to set fruit because of extreme temperatures. If it's too cold, the pollen dies and doesn't correctly fertilize the ovary. If it's too warm, the pollen clumps and doesn't fall on to the stigma easily. If you've been having high and low temperatures, they may be to blame.

If it's too warm, the pollen clumps and doesn't fall on to the stigma easily. If you've been having high and low temperatures, they may be to blame.

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High temps don't cause pollen to clump, it's high humidity that does that and clumped pollen is then much less effective in enabling self pollenization.

Offrel, high sustained temps above about 85F to higher can cause pollen to become what's called denatured, meaning it's inactive.

And high sustained humidity can cause pollen clumping as I just mentioed.

And if night temps are above about 70F then pollenization doesn't occur either.

The low temp restriction I don't think would be that common for most of us at this time of the year.

The blossom cycle is about three weeks and since blossom formation on a plant is asynchronous when high temps fall and/or humidity falls, then you should start seeing fruit set.

Shaking plants or vibrating blossoms is NOT going to work unless pollen is viable.

And the product Blossom Set was devised to be used in those areas where the Springs are very cool, such as the PNW, and it does help by inducing what's called parthenocarpy, which means fruit development in the absence of fertilization of the ovules in the tomato ovary by the germ tube formed by pollen.

Carolyn

Geez, Carolyn, you sure can thoroughly answer a question. How in the world do you know so much?

Thanks, Carolyn, you always tell us all just exactly what we need to know.

You mention high sustained temps and my question is how long is "sustained"? An afternoon (~ 4 hours), or 10 hrs, 24 hrs, 72 hrs,... ? Thanks, JoAnne

tomahtohs,

If you click on Carolyn's "My Page", you'll see a very nice intro from her.