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Growing Tomatoes

Do cool night time temps affect fruit set?

13 years ago

I live in eastern Canada (Newfoundland, actually) and grow my maters in a greenhouse. My plants are just starting to set the first truss of blooms. I am wondering if cooler temps affect fruit set. My nighttime temps are still going down to the low 50's and high 40's (Some of the varieties that I am growing include: Black Sea Man, Lemon Boy, Cherokee Purple, Gregori Altai, Miracle Sweet, Juanne Flamme, San Marzano, Sparta, Cobra, Black Plum, Marmara, and Kastalia.

Thanks

Rob

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Comments (6)

col_sprg_maters
13 years ago
Here in colorado we are told that until the nights are consistently above 50F, fruiting willl be very slow.

Some say 55F

another zone 5 tomato grower (lots in containers)
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digdirt2
13 years ago
Per the FAQs here:

If the night temps fall below 55 or rise above 75 or if the day temps are above 90, the pollen becomes tacky and non-viable. Pollination cannot occur.

So as already mentioned until your nighttime temps rise more you'll likely see very little pollination. One way to get around this problem to some degree is to use the so-called early, cold tolerant varieties.

Dave
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Like Kevin said, keep in mind that day time air temp is far from the only contributing factor to Blossom Drop or to the lack of it either. It hasn't been 95-100 for the full 24 hour period. Just count your blessings and keep your fingers crossed but don't jump to any conclusions. And the regional reported air temps or even the temp recorded on a thermometer hanging somewhere nearby isn't necessarily accurate as far as the plant is concerned unless the thermometer is hung in the middle of the plant. :-) Dave
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Duh, Now I see the confusion about the lights. HUGE difference in heat output between the two types. It probably takes 10-15 of the ones shown in the picture to equal one of the old style I was talking about. The big issue I see with the little ones is that they are wired in series and one bad bulb causes the whole string to go out. A single 13 watt CFL causing 15 degree temp rise makes sense. It might raise the temp more in our lower humidity. 5-1-1 sounds much better for holding some moisture than Gritty. I'm making Gritty work for succulents out of direct sun but everything else needs more water retention in my sunny/hot/dry climate. When I had 30 plants in black plastic pots this Summer, I struggled to keep them happy. Putting them in a East-West line and shading the end pots helped a bunch. I think the low humidity makes a big difference because the sun bakes plants here much harder than my previous house on the beach. Our average rainfall for June, July, Aug, Sept is a TOTAL of 1/4".
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The best pepper info I could find is this: "Flower and fruit development, the key to flower set is nighttime temperature, which ideally should be between 65 and 80 degrees. Fruit set is enhanced by increased sunlight, however fruit will not set when night temperatures are above 86 degrees F." from http://www.chilepepperinstitute.org/documents/growing-tips.pdf Also from the institute: "Fruits do not set when mean temperatures are below 60oF or above 90oF. However, flowers drop when night temperatures are above 75oF. Fruit set may be stalled if temperatures rise above 90oF after several flowers have set and fruits are developing. This causes a split in the fruit setting continuum and is called a split-set." http://www.cahe.nmsu.edu/pubs/_h/h-230.pdf I live in desert Arizona where currently and for much of the summer now the night temps are near 90F and the high day temps >110F. Once in a while I get some fruit to set throughout the summer. I do often spray down the garden at night to cool it off (keeping plants dry, but the surrounds/ground damp) I wonder if these moments of cooling can help get fruit set. I wonder if it is the average day and/or night temp or morning temp or peak temp that is most important. There is really a very short spring growing season here for peppers. There is very little time between the ground being warm enough (>55F, late Feb) and the daytime temps being below 100F (late-Apr). I use spring mainly to establish healthy plants and root systems to keep the plant alive thru the summer. Then there is the 2nd primary season - Fall - when the temps cool down in September and I get a massive load of fruit form those plants I kept healthy thru the summer - they keep fruiting from Sept thru the first frost in late Dec. I just wish I could extend the fruiting of the spring season a bit - on long season plants I don't get any fruit and on short season still only 3-20. Al
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Comments (1)
Hi katib - assuming there are mature blossoms during that period and assuming that it is the temps causing the problems, that is long enough. It is all in the bloom timing.;) Dave
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wordwiz
13 years ago
Dave,

>Pollination cannot occur.The FAQ is wrong, Period.Temps in my GH have been above 115 and I'm still getting baby toms. They are not doing well, in part because I have quit watering, but they still set fruit. Humidity probably plays more of a role than temps. In the GH, it is very low, so the pollen isn't sticky.

YMMV,

Mike
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digdirt2
13 years ago
Mike - while I agree that humidity also plays a big role, especially when talking about HIGH temps. But the FAQ isn't "wrong". It is simply based on what is the standard, the norm of tomato growing - outside in a garden.

A greenhouse is a totally different environment of course but the info is still generally relevant, especially the low temps part.

Dave
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colokid
13 years ago
Quote:
If the night temps fall below 55 or rise above 75 or if the day temps are above 90, the pollen becomes tacky and non-viable. Pollination cannot occur."
"Pollination cannot occur."
Way to much black or white. Should say that it makes pollination more difficult.
If that were 100 percent true, there would be no tomatoes in Colorado. The last couple of days, nights has been in the 50s and days over 90. Very normal for here. and I have tomatoes stetting like a normal year. We do have low humidity though and that could be a big factor.
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jwr6404
13 years ago
Nighttime temperatures above 50 degrees in my PNW area have been rare this season,normal for this time of the year,and my fruit set pretty good on 12 of 15 plants including Brandywine. The Black varieties are doing best.
Jim
0

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