I got a little excited this year, I already put my tomatoes outside in some 15 gallon pots. Unfortunately, we have pretty big temperature swings and we are suppose to have 37 degree weather tonight. Is that close enough to freezing that you would bring them inside for the night?
Thank you
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I’d protect them from temperatures below 50°F.
If it’s going to be 30s 40s, i don’t think your tomato would grow much and can only risk damage.
Duration of the exposure matters and consider your microclimate, which could make things better or worse than the general weather forecast.
Definitely move them in, at least to garage if you expect sunny day tomorrow and it is going to warm up.
Any exposure below 50F risks stunting new tomato plants. Especially if you have not hardened them off over a period of a week or so, gradually exposing them to ambient conditions an hour or so each day. Once stunted, they are done for a good portion of the season often taking weeks to begin to blossom. Definitely bring them back to a location where you can protect them
Dennis
Kent, wa
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I realize I am late to answer, but I always cover or protect my tomatoes when the temperatures are going to be below 40 degrees. My yard seems to be much cooler than the forecasted temperatures. I have a thermometer in the backyard that relays the temperature via wifi into my house. I also have very old bi-metal outdoor thermometer that still works amazingly well. I find that my micro-climate in my backyard varies as much as 6-8 degrees from what the weather station is reporting for my backyard. Our springs always have cold nights where we live. My tomatoes do not seem to mind cold temps down to about 34 degrees. As long as they do not freeze they come right back as soon as it warms up during the day. I get amazing harvests nearly every year. We bottle our ripe tomatoes and eat them year round, so I really pay attention to how they produce.
I don’t know what is the best temp to bring them inside but I moved all my plants inside when it was predicted to go below 45F.
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Biggest immediate concern at 37 degree is frost.
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Tomato plants produce a chemical compound called “rubisco” which is transported through the stem. Temperatures below 45 degrees severely restrict the stem’s ability to transport rubisco. The problem is that once deactivated, transport capacity stays restricted until certain things occur. At low temperatures, it stays inactive pretty much indefinitely until the plant dies (below 45F). From 45 to about 70 degrees, it gradually begins to function causing severe development delays for the plant, typically 2 to 4 weeks of low or no growth. But here is a magic secret. Expose the plants to 90 degrees for a day and voila the stem begins to function again. So the magic temperature is 45 degrees. Dig around on the net and you can find some very well researched papers that document this process.
But that is not the end of the story. Some tomato varieties are capable of maintaining growth all the way down to 32 degrees and a few have a gene “ft” that permits fruiting at just 41 degrees. Earlinorth is an example of the ft gene. Sub Arctic Plenty is an example of a tomato plant that is tolerant of low temperatures. Solanum Habrochaites is a wild species that lives at elevations in the Andes up to about 4000 meters. It is more cold tolerant than any domestic tomato. Some effort has been made to move the cold tolerance into domestic tomatoes but to my knowledge no varieties have been released.
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Thanks
My experience is identical to yours. Above freezing, we are as much as 10 degrees lower than predicted. As temps drop, it’s more like 6 degrees. The orchard is also at least 6 degrees below the temp that displays from a thermometer higher in the yard. I’m so thankful now to have a weather station at the trees so I know what’s going on.
I have learned recently that at least one of my neighbors took out all his fruit trees due to our cold temps.
On weather underground we are listed in Virginia as Raphine, Brownsburg. Here’s the weather station view.
. That low in April was 22 but it got cut off the pic.