IMO wait until the nights are all over 50

How big are they? are they hardened off? I live in Southern MD, and we have some "test" tomatoes out right now. The frost the other night did not please them (they survived), but i think we are safe after Thursday 4/23. 80's is a good sign winter is ending in the East.

FWIW, there are at least three recommended indicators of when hardened-off tomato plants will thrive being planted out. First, night temps need to be at 50 or above, daytime temps higher than that, and soil temps at a couple of inches deep need to be stable at about 60 degrees (a simple probe meat thermometer can test it for you). The soil temps are a result of warmer air temps and the soil warming effects of sunlight plus minimal heat loss during lower night temps.

In other words, we need to pay attention to temps not only for the upper part of the plant but for the root system, too.

Eventually, these parameters become second nature to take into account, though in the beginning they may seem to be a lot to keep in mind. There is an integrated process for it all! I think of it as a minimum of 50, night; 60, soil; and 70, air. Soil is the middle number.

wow, I am so grateful for all your inputs. Ok, I've been hardening them off for about 2 weeks now - during day time, and today is the first day I am leaving them outside in a portable green house. I will do so for next couple days. I have a raised bed ready for them, and will check the soil temps tomorrow. They are big, I just repoted them and they keep growing and I can see the new roots through the plastic. I think the tallest one is a foot tall , others are at least 6 inches.

We always harden ours off to 40+. The greatest danger in lower than 50 temps, is the possibility of frost. It's not the 40's temps that hurt them.
I watch them carefully. When the night temps hit 40's consistently, out they go. In my experience, warmer temps aid in stem and leave growth, I prefer to give them stronger root systems before they proceed to that level. Therefore, I advocate cooler temps, IMHO. :-)

Anney,

I have been chanting "50, 60, 70" to myself (incessantly).

Thanks for that great tip.

-alg

I planted them all out this weekend. Soil temp in bed was showing 70-80. I bought cattle cages, secured them to re-bars (sp?). I mulched them with pine needles. This coming Thursday-Friday and all weekend is supposed to be T-storms and Tue-Wed next week some rain. Are they going to drown? They are in a raised bed, plenty of sun. Any measures I should take?

If it helps, i'm in middle TN., and all my veggie plants (including 3 kinds of tomatoes) are outside for good now. I'll still be keeping a eye on the temps over the next 2-3 weeks though. If we have an unexpected drop (which it would be quite unexpected at this point, looking at the 7 day forecast today), I might yank them indoors overnight for one night. I doubt i'll have to do that though.

Here in San Francisco, if I waited until night temps were consistently above 50 I wouldn't be able to plant out until June or July. If the risk of frost is low and you have hardened the plants for a week or two and and the location is getting enough sunlight, plant.