Temperature plays a smaller role than many think but keep in mind that when you set plants out, unprotected, the wind can be a problem, especially with low temperatures.

Some means of protection is usually best but I like to be there to monitor the response of translocated plants. You can tell alot in the first 20-30 minutes when plants are placed into a new environment.

With cool-season plants like broccoli, 45 is fine. I like to harden off other cool-season crops (but not broccoli due to the buttoning risk) with temps. in the low to mid 30s to encourage frost tolerance.

With warm season crops, especially peppers, try not to expose them to anything under 50 degrees. Soil temperatures under 55 degrees drastically decrease their ability to uptake water.

As already said, 45ð and up is ok for cool weather plants. Things like melons need to be 50ð or more.

I understand your problem of setting out plants when it is too cold but gets warmer shortly. I am retired and can care for the plants perfectly most days. I start taking them outside from the get go. Also unattended plants may get hit by a storm...not good at all. I have a south and a north place to protect from strong winds

Hope you don't mind if I just link you to a recent discussion of this on the Tomatoes forum. Saves typing it all again.

Dave

Here is a link that might be useful: Hardening off while working

I've seen accounts that say prolonged exposure to temps between 35 - 50 will cause bolting and buttoning in brassicas. From which I assume that even lower temps would be worse, which is what we're getting next week.

My first batch of seedlings are already getting oversized. I've put them out to harden, but I doubt if I'll be able to plant them within a month.

Thanks all!

Dave that link is great. I had no idea that the first day or two of hardening off required NO direct sunlight. I aways figured an hour or two of direct sun was fine (and then build up time from there)

bart, If the plants are of some size, then they need to be broken in more slowly. With my setup they can be out all day from the get-go when the weather is suitable....you don't shade newly germinated seedlings that are garden sown!

This post was edited by wayne_5 on Thu, Mar 20, 14 at 21:42

I'm a working stiff too. When I start hardening off my plants, I set them outside on partly sunny or cloudy days and have them right next to the house. That way they only get a few hours of direct sunlight. I bring them in at night for the first week or two. I gradually (every couple of days) move them further away from the house so they get more sunlight.