I think they'll be OK. I routinely plant out when the nighttime temps might dip into the high 30s. As long as they are hardened off, they'll do OK. They won't actually *grow* until it gets warmer, but they won't get killed.

Ok thanks. I watered them and covered them with a light row cover and shut up the cold frame. Cold drenching rain here. Perhaps my least favorite weather but we do need rain. Crossing fingers.

What do you think is the minimum safe temperature Dave?

To be honest, it seems risky. But...in the name of science...

Minimum safe for me, if exposed, is 50. If still in the greenhouse, 45. That is when the heat kicks on. Covered in a cold frame I still shoot for 45 +/- a couple of degrees. To me it just isn't worth the risk even tho I may have plenty of replacements available.

But I also have to wonder if you have had them in the cold frame "for weeks" and they can't go into the garden "for weeks" yet, how old these plants are? How big?

Dave

If the forecast is calling for high 30s, it should be several degrees warmer than that in cold frame.

Check the hourly forecast (Weather Channel). You will see how many hours during the night the low will stay. Normally the low lasts maybe for 3 --4 hours.

Further to reduce the cooling in the CF , you can cover it wit tarp or something else. Tomato can take high 30s with no risk AS LONG AS IT HAS BEEDN DARDENEDED OFF, say down to low 40's . JMO

Sey

As far as size - I just moved most of them into 6" pots. We have a fairly short season here - getting a lot of tomatoes ripe or at least harvest ready before frost and blight requires skill, luck and trickery.

They have been out during the day only for a couple of weeks. And out at night for the past 5 nights that were forecast as 40°F.

I am reconsidering. I parked my car so I can see to get them in..... I am wishing I waited to pot up a few more days but I wanted them in more soil.

Thanks all.

Ok - it got below 35°. I moved them inside. It was 11-12° warmer in the cold frame than out @ 10pm - better than I thought it would be.. Tomorrow night is supposed to be cold then a warm up. So hopefully I am almost done moving them in and out....

If you had them planted outside with temps dropping into high 30s*F I would tell you to cover but since you have the frost protection of the coldframe you'll be fine. Actually when you eliminate the frost threat you can dip slightly below 32*F inside the coldframe without damage to plants. I've heard one researcher report that the plant actually adapts to handle colder temps when it senses a barrier above it such as a cover or film.

If you continually subject the plant to cold night temps you gain little other than keeping the plants alive. You could monitor temps and you might learn that they will be higher by a *F or 2 or in odd occurances the temps inside may actually drop below outside temps as it has reported by research to occur in greenhouses.

how cold is too cold?

well that is an easy question. too cold is when the plant freezes and dies.

I also live in central Maine & completely goofed (forgot 1 tray) last night! My seedlings look pretty sad this morning, brought them into the warm house for the day, we will see what they look like when I get home tonight....ugh!!!

If planting is still a few weeks away, I tend to keep the plants indoors under fluorescent light to help encourage growth. If it's sunny & warm outside during the day I move them outside, again to encourage growth. With outside night temps near freezing, it's likely very little growth will occur and the plants just hibernate. After the warm treatment, the last week before planting they get hardened off.

lisaw2015 - where do you live? I live north of Skowhegan. And I have tomatoes! My lights are all taken up by peppers.

Here's my dog JoeB with about 50 of my tomato plants which spent the day in the window.

It frosted last night and snowed a bit today. Sigh....

I should say that if you are in central Maine the soil temperature is going to be quite low, and it's going to stay that way for a while. Low air temps combined with low soil temps are not good for tomatoes. An occasional chilly night with the tomatoes sitting in comfortable soil is not problem, however. That's the difference between you and me. When I plant out, the soil is in the 50s and 60s. I'm guessing your soil temps are in the 30s-40s.

this seems to be the worse spring for growing tomato transplants. the weather has been horrible. yesterday and today the winds were almost 20 mph all day whipping the plants around even with wind breakers as best I could do.

https://www.youtube.com/watch?v=2AkLE4X-bbU

Patti Page sings

How much is that doggie in the window arf arf

the one with the wagglie tail.

Yup. Soil temperatures vs short growing season (and late blight)..... Growing warm season crops like tomatoes or peppers is an eternal struggle here. A matter of technique, varieties and sheer luck. I will probably put up a low tunnel next week to try to get the soil temp up a bit. Many people use the wall of water or cloches to protect young plants.

I heard on the radio last night that 90% of the peach trees in the state died last winter (a 'mild' but long winter) but many find the risk worth it to get the chance for a bumper crop of peaches.

agmss15 - I live just north of Skowhegan too!!!! Email me!

to the OP, I can't seem to figure out how to email you. I am so excited to find someone on here that lives local!

Hmmm.... I have been trying to figure that out too.... Are you on FB? If you send a message to Sprig Woodwork - we can go from there.

Sorry - this post got a little sidetracked. I will be lugging the tomatoes out today for a few hours. And will possibly move them to the coldframe again tomorrow. It looks like we will be back to nights in the 40°s.

If I lived in Maine, I would definitely construct a winter shelter for extending the growing season and for getting a head start on tomatoes in the spring. Locally, you have one of the world's experts on this in Eliot Coleman, who helped pioneer the technique and published a few books on how to do this. We tried low tunnels but like the flexibility of the high tunnels. We built one in Utah (zone 6) and it has worked wonderfully to warm the soil and provide a sheltered climate for putting out tomatoes early. Here's this year's plants grown from seed indoors, transplanted in April a few weeks earlier than the last frost date: