First, be aware that that particular source of info is not highly regarded as accurate. Much more legit sources of info are readily available online.

As one example, I have linked the FAQ here below. Note night temps must be maintained above 55 and below 75. So 60-70 degrees at night is considered ideal. Day temps must be maintained below 90. 75-85 would be ideal.

Providing active air circulation in and around the plants to aid in pollination is also crucial for fruit set when grown indoors. Fans work well, rattling /jiggling cages, flicking blooms with the fingers, etc. all help with pollination and fruit set.

Dave

Here is a link that might be useful: Blossom Drop FAQ

Your advice was well taken Dave - the air circulation must have helped as all five of the tomato varieties we planted set fruit on the first cluster !

I agree that you want to try to keep your night temps elevated but the 55*F temperature may not be all that critical for most hybrid varieties you mention and certainly for the majority of cherry types. With German Giant I'd be a little more concerned about getting catfaced fruit at lower temps. There were many night this spring where I barely held above 40*F and I see no affect on fruit set. I'll agee that circulation fans serve many purposes- you can eliminate cold spots within the greenhouse and you aid pollination. I'll admit that I still hold an old electric toothbrush to the first few blossom clusters to insure fruit set (one can see the pollen cloud emitted during the process) but even clipping plants to stringline and suckering tend to create enough agitation to aid in fruit set.

Bmoser - would you please post some photos of your tomato plants? Would like to see your vine support methods and the varieties you plant. Tks!

These are a few shots of the greenhouse tomato plants. Shipping tags identify varieties and number planted. I guess only the one pic uploaded of later planted heirloom varieties.

I wanted to add that if you allow continued cold night temps you will loose much of the benefit of early planting so you should strive to keep night temps close to 60*F even if you fall short on occasions.

Awesome - thanks for the photos! I am trying to duplicate what you are doing on a much smaller scale. If your photos are recent - my plants look much like yours today - the bottom clusters are setting fruit and are about the same size. I think we were successful setting fruit in-spite of the cold nights - however - the German Giants are slower but appear to be setting. Thanks for sharing.

I would be interested to see how you prune the leaves/plants as the cluster set fruit tier after tier if you could possibly post a few photos as that happens?

I did not get to include a photo of the earlier planted greenhouse where I have 520 tomato plants, mostly hybrids. The last photo I entered was of a Big Beef fruit cluster in that planting; those are probably 6 or more weeks from harvest. I do hope to be picking from 200 cherry/grape plants (middle rows) by the end of the month. I sucker out all branches until things get too busy (usually July) and then end up leaving a few branches on most plants. I don't cut leaves off unless they are on the plastic(ground).

I found this to be an excellent article for GH Tomato Production and wanted to share:

http://www.uaf.edu/files/ces/publications-db/catalog/anr/HGA-00435.pdf

Our first ripe tomatoes in 2013 - Yeah !! We pushed the plants during cold temps but they came through for us and set fruit! The other varieties are not far behind.

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Beautiful!

Just a few thoughts on the original question of tomatoes setting fruit at low temps. There is a variety, Earlinorth, that sets fruit down to 40 degrees. If you do some serious digging, you can find several Russian varieties that have significant cold tolerance. Also, there are several varieties available in the U.S. that are modestly cold tolerant in terms of setting fruit.

I am doing some work with tomatoes to identify genes that contribute to extreme cold tolerance. I currently have 200 plants in my garden for evaluation. This includes Earlinorth, PI120256, numerous U.S. cultivars, and several Russian varieties. So far, I have seen 3 distinct traits involved in cold tolerance. One is the ability to set fruit at low temps, another is improved root efficiency, and a third is leaf tolerance to cold temps. Each trait appears to be affected by different genes.

DarJones

Very interesting fusion_power - We have done limited research on these Russian varieties but opted to figure out ways to inexpensively as possible heat the GH to min temps - and/or start the seeds a little later next year. It seemed with what we read - the more tolerant to cold varieties came at a sacrifice - mainly fruit size and possibly flavor?

You are more knowledgeable and may know of varieties that offer both fruit set in cold temps and good fruit size/flavor? Regardless - your work identifying genes should result in improved hybrids in the future - for setting fruit in cold temperatures? It seems expanding the low and high range for setting fruit in tomatoes would help gardeners everywhere.

Is the main purpose of your research to improve the temperatures for setting fruit?