It isn't so much a "perish" issue as it is a stunting issue. That cold easily stunts plants so they never deverlp or produce well.

IMO it is far too early for your tomato plants to have gone out in your zone. We are just now getting ready to plant them in this zone.

But to answer your question I'll reference several of the discussions about this currently going on the Growing Tomatoes forum here: 60-65 degree soil temp and 50 degree air temps is the standard recommendation for minimums. They may tolerate a 45 degree night with cover based on MPE but consistent night temps above 50 degree is what is recommended to avoid problems.

Dave

I once set out my tomatoes about a week too early one year. We had a 4 inch rain and then it froze. Most of the tomatoes regenerated and made fine plants...more bushy for a while. a few plants died.

So - I have planted out all of my tomato plants - and did so over the weekend.

Whoops. Hope springs eternal in the human breast, but last frost dates are in the human mind.

Mine are going out in the next couple days in WOWs, then the WOWs come off after danger of frost, ~mid-May hereabouts.

Dan

It's much too early for z5b tomatoes. I plant mine the week before Memorial Day

I planted out my tomatoes a month ago, inside my high tunnels. I haves covered them with one or two layers of row cover almost every night since then. I have managed to keep them above 50 degrees. They are growing great. I am starting to see blooms.

I have taken tomatoes down to 20 degrees with row cover and inside high tunnels. I did loose a few along the outside.

I would not plant tomatoes outside until at least May 1.

This picture was taken last week. The plants are now almost above the low tunnels hoops.

{{gwi:36911}}

Jay

BSN, with all due respect, what are you thinking? From Wisconsin to upstate NY we are going through the most miserable, wintry spring in decades, and you put out the tomatoes in mid-April? Without cover? Jay can do it, and so probably can Dan, they have double layers, thermal ballast, and a relentless sun that charges the hoop house during the day. we get cloudy days maxing out at 37. I stuck my hand in a bed that has unfinished compost, topped by clear poly, under a hoophouse, and it was still cold. Not even the compost is able to take off.

Yep, completely stupid.

I just saw that they were well outgrowing my germination station downstairs and I couldn't move the lights any higher.

We've had pretty good weather for the past couple of weeks with night temperatures always over 40 degrees.

Then after the huge storm that blast through here last night, the temperature dropped from 80 down to the high 30's in seven-eight hours.

After getting home today, I dug up all the tomatoes and put them in gallon buckets in the house. They certainly look pretty sorry.

Adding fuel to the fire is that I didn't have enough tomatoes germinate for me this year.

{{gwi:40414}}

Here is a link that might be useful: My Garden Blog

If you plant them out this early, put them under plastic (low tunnels/high tunnels) and you'll be fine. Let them bake on these sunny days that come every once in a green moon.

I wouldn't say 35 degrees is harmless Darell. If the plants are in blossom they will likely loose many blossoms and have catfaced fruit on most others. Also I found that if you consistently fire up the stoves at night (in greenhouses)it will pay dividends in much earlier harvest, often three weeks earlier depending on the weather.

Wall O' Water

Dan

bmoser, re blossom damage, agreed..... if the plants are blooming. You might dig around on the web a bit, there is a study you can find that shows cold treated seedlings are more productive and produce fruit earlier.

DarJones

For years I have carried my tomatoes outside as soon as they germinate (and carried back in at night), as long as the temp is above 40 degrees. By the time I set them out at the end of May, they are unbelievably vigorous, with stems as thick as my thumb and many are flowering. Certainly no set back.

Sounds to me that what the original poster's problem was failure to harden them off.

Dan is right. If you're going to push your luck that far, the only way to go is with Wall o Waters (various names these days) or tunnels. It's not too late to start over.

I'm in 6b, wouldn't think of setting out maters without serious protection before early May. 55F or below and they are stressed.

I almost had the same situation.
Glad I read the post. I'm in Elmwood Park, IL and my tomatoes are about 10-13 in tall, inside the house under light.
I'm struggling with the idea of taking them out and set them in a small green house (about 3 shelfs; structure is covered in plastic)but I'm afraid of killing them.
Can I take them out in the green house and than bring them in at night?

I also have green pepper, hot pepper, egg plants, salad, cabage.

What are you suggesting?

Thank you for reading my post.

Good thing I dug them up and brought them in last night.

We had temperatures of about 30 degrees overnight.

I do have floating row covers that I was using for the celery, onions, and lettuce - but I removed all of that about two weeks ago and they are doing fine.

But, I couldn't put a row cover over the tomatoes because I already put the cages up and everything. I also tie all the cages together and to some rebar in the ground to help keep them upright - so all of that had to be undone yesterday.

You are correct about hardening them off. I did not harden the plants off this year before setting outside. Now, I did take them outside a few times during the day so I could shut the fluorescent lights off - but that still isn't really hardening them off.

I planted 19 tomato plants in my garden in southern California on March 19 and 20. Since then we have had at least 20 days where night time temperatures were in the 44 to 49 degree range, and at least one or two nights when it dropped to 41 degrees. All but one plant survived, and the one that didn't died from some stem rot. Many of the others had some of their leaves turn yellow and sickly looking, but I cut those leaves off and now all the plants are looking healthy and about five of them already have tomatoes on them. I didn't put any protection on them.
I did thoroughly harden them off before planting them by putting them outdoors on my patio everyday when the temperature was above 50, and then took them in at night, from the day they sprouted.

I think plants outgrowing the lighting system too early is a common dilemma for many folks. I would suggest that rather than panic simply transplant into larger individual pots and continue to set the pots out during nice days and bring them in at night or when foul weather occurs. Sure it is a bit more effort and hassle but it is much better than taking risks and ending up losing your beautiful plants after spending all that time and effort starting and growing them. Add to this the fact that the topic is tomatoes and I don't know about other folks but I will do ANYTHING to ensure I get a crop of vine-ripened tomatoes. Even if everything else in the garden fails. ;-)

And yes, it is all about the average last frost date for your area, IMO. That date is the guide for when to plant out, but it is also the guide for when to start seeds to avoid starting too early and having them outgrow the lighting system.

All my gardening plans pre-season, all season, every season are dictated by the average last spring and average first fall frost dates. This natural cycle can be cheated some, the season can be extended a bit, but ultimately will defeat any human efforts to avoid it and will burn anyone who ignores it.

Hope your plants make it!
-Tom

I'm with laceyvail. I put my seedlings outside as soon as they break ground. As long as it's not windy and raining & above 40 degrees...out they go. By the time they're 4" tall, their stems are fuzzy & sturdy.

I don't use grow lights. Every one I know that uses grow lights have leggy plants because they plant the seeds too early. :)

I just planted my seeds April 5th. They're now about 2 1/2" tall. Movin' right along. :)

Every one I know that uses grow lights have leggy plants because they plant the seeds too early

It's not because they planted too early. It's because they used "grow lights". Most experienced growers that use lights know better than using "grow lights", have healthy 6-8 week old transplants that are 10-12" tall to go in the ground when weather permits, have fruit much earlier and a longer growing season.
When are you going to have ripe tomatoes? I should have some by late June (if something bad doesn't happen) and I got a late start.

Most experienced growers that use lights know better than using "grow lights", have healthy 6-8 week old transplants that are 10-12" tall to go in the ground when weather permits, have fruit much earlier and a longer growing season.

I was given a light and bulbs as a gift one year. I still have it. You have to know what to do with it. The seedlings have to come out from under and into the window sooner, is all.

Tangent aside, Wall O' Water. Problem solved.

Dan

LOL! My plants go outside to harden off not into a window.