What is hot for tomatoes?

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Barmaley
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What is hot for tomatoes?

#1

Post: # 47216Unread post Barmaley
Fri May 21, 2021 11:53 pm

We are getting few days with 88-91 degrees. Is it too hot for tomatoes? Do I need to bring them for few days back home to same ability to set fruit? If I keep them outdoor - will they recover after the heat wave?

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Shule
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Re: What is hot for tomatoes?

#2

Post: # 47220Unread post Shule
Sat May 22, 2021 12:58 am

89 is pretty much the perfect temperature for tomatoes, in my garden. Some varieties have trouble setting fruit when it gets to 90 and above, but don't stress about it. It's just part of life. The temperatures will go down again, eventually, and some varieties will set fruit in the heat anyway, especially if you take good care of them.

Which varieties are you growing?

The plants themselves should be fine (in a northern climate; I can't speak for the South). My plants were fine when it was 116, for that matter. The only thing you probably need to worry about (since you're in the North) is fruit set during the heat, unless it's both hot and rainy/humid at the same time (so I've read)--then that could breed diseases.

Extra potassium helps with the heat, in my experience, but it won't necessarily make plants set more fruit in it. But, they probably will show fewer signs of stress, and probably have earlier production.

Many varieties won't set fruit until the heat goes down anyway--not because they lack heat-tolerance, but because they're midseason or late tomatoes. It's mostly just the early and early midseason tomatoes where heat-tolerance is a big concern, in the North, especially if they're determinate and set all their fruit when it's hot.

If you only have a day in the 90+'s once in a while, rather than weeks on end, then you shouldn't even bother worrying about it.

I wouldn't bother worrying too much about heat-tolerant varieties, though. Even the heat-tolerant ones don't usually set that much fruit in the heat (but they do set it). Taking good care of your plants is key.

Oh, and remember, there are at least two kinds of heat-tolerance:
1. Heat-tolerance for humid heat.
2. Heat-tolerance for dry heat.

Just because something is heat-tolerant in a humid area, doesn't mean it's heat-tolerant in an arid area, and vice versa. Sometimes they're both, but not always.

It's a common misconception that dry heat doesn't even affect production, but that's false. It definitely does, even if it has nothing to do with humidity making pollen clump.
Location: SW Idaho, USA
Climate: BSk
USDA hardiness zone: 6
Elevation: 2,260 feet

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bower
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Re: What is hot for tomatoes?

#3

Post: # 47222Unread post bower
Sat May 22, 2021 5:39 am

Tomato pollen is killed at temperatures above 95F. As Shule said, the plants will be fine but you may not get fruit set until the temperature goes down a bit.
Bear in mind that there are natural cooling factors (breezes, shade) that can make a difference at marginal risk.
Tomatoes use their leaves to shelter the blossoms when it's hot. If they're close to one another, they will also lend a hand to a neighbor, by cupping their leaves over the other plant's little ones. This is one reason I don't like to prune too much. Or prune carefully, so that the leaves that are helpful for shading don't get removed.
AgCan Zone 5a/USDA zone 4
temperate marine climate
yearly precip 61 inches/1550 mm

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pepperhead212
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Re: What is hot for tomatoes?

#4

Post: # 47234Unread post pepperhead212
Sat May 22, 2021 10:16 am

Around here, it's when it gets in the high nineties for several days in a row that many of my tomatoes start dropping blossoms. Low nineties doesn't seem to bother them. This is why I grow so many cherries - even if they do have this problem with the heat, they recover much faster, getting ripe tomatoes much faster, after the heat drops.
Woodbury, NJ zone 7a/7b

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Rockoe10
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Re: What is hot for tomatoes?

#5

Post: # 47235Unread post Rockoe10
Sat May 22, 2021 10:55 am

Last year, we had several mid 90°F days. And dry. The plants had fruit already forming and did well in that regard. New blossoms didn't take as often, and the plant leaves started to curl from the heat.

Once it started cooling down, the plants started growing again
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Rob, ZONE 6A with 170 days between frost dates, Western Pennsylvania

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Cole_Robbie
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Re: What is hot for tomatoes?

#6

Post: # 47269Unread post Cole_Robbie
Sat May 22, 2021 7:33 pm

Humidity is an important variable, when assessing temperatures. Pollen dessication happens much faster in very dry conditions.

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Barmaley
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Re: What is hot for tomatoes?

#7

Post: # 47334Unread post Barmaley
Sun May 23, 2021 10:28 pm

It is crazy here - after 90 degrees it goes to 70-ties and high 40-ties at night! Nevertheless, Cherokee Purple put a lot of flowers and set first tiny fruit, At the same time Better Boys hide their flowers. I am not sure if such jumps in temperature is good for tomatoes?

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bower
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Re: What is hot for tomatoes?

#8

Post: # 47355Unread post bower
Mon May 24, 2021 8:39 am

70's days and high 40's nights are just about goldilocks temperatures for tomatoes. :) Actually they prefer night temperature of 60 F (especially more sensitive varieties), but the larger difference between day and night temperatures is a factor that encourages reproductive growth (flowering and fruiting) instead of vegetative growth (more leaves and longer stems). So they should be doing what you like them to do. :) If you think nights are a bit chilly for them, fill some 2L bottles with water and leave them in the sun around the base of the plant, this will keep the soil warmer.
AgCan Zone 5a/USDA zone 4
temperate marine climate
yearly precip 61 inches/1550 mm

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karstopography
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Re: What is hot for tomatoes?

#9

Post: # 47358Unread post karstopography
Mon May 24, 2021 10:23 am

Continuous nights above 70 degrees or a little more pretty much shuts down fruit set here. We’ve had little relative warmth lately, it’s been in the 70s continuously for days and the nights as well with the near constant rain and tropical air off the GOM. The Tomatoes on the vine aren’t ripening much or very, very slowly. Plants are still putting on new growth, but not much in the bloom department. Maybe Dixie Red by the looks of it is still setting a few fruit, everything else seems not to be.

Prime tomato setting weather here is days around 80 degrees in the afternoon for highs, give or take a little, and nights in the low to mid sixties for lows. Seems like once the weather veers too hot with days in the low 90s and nights in the low 70s you can kiss tomato fruit set goodbye except for maybe some cherry tomato types. We have not had any days in the 90s yet in my particular locale, but the nights haven’t been cool either. Wet tropical weather isn’t ideal for fruit set or ripening for that matter. Lower leaves are showing signs of stress and disease.

Heat or lack thereof, relative humidity, dew points all might be in play. Right here near the Gulf of Mexico, it’s not so much the day time highs that hurt the fruit set, it’s the too high and too consistent nightime lows that are the bane of tomatoes, fruit setting tomatoes. Clumpy pollen, disease issues, high dew points, above 70 degrees for sure, aren’t friendly to tomatoes.

Out west, high dew points just aren’t something that happens much at all. High dew points, mostly thanks to the Gulf of Mexico, spread over the eastern half of the country and as Spring transitions to summer they seem to get established firmly in the south and the humid heat along with it. The north gets bouts of it, but they tend to be transitory, just depends on where you are and the particular summer.

Out west, as long as they have access to water, they can grow anything it seems, thanks to drier air, lower dew points. No wonder California almost laps any other state in agricultural production. Florida actually sometimes tops California in tomato production as Florida gets a late fall-winter crop and then another big crop in April and May. No other state is close to those two in tomato production.

https://edis.ifas.ufl.edu/publication/FE1027
Zone 9b, located in the Columbia bottomlands, annual rainfall 46”

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goodloe
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Re: What is hot for tomatoes?

#10

Post: # 47379Unread post goodloe
Mon May 24, 2021 4:43 pm

Good info from both [mention]Bower[/mention] and [mention]karstopography[/mention] . The hard heat here in Mississippi in July and August really does a number on fruit set. I run a big fan at night out in the Patch from about mid-June on...it seems to help by giving my plants some breathing room on nights where the temp barely drops below 80...
I have 2 seasons: Tomato and pepper season, and BAMA Football season!

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