Temperatures for Seedlings

Hi everyone,

I put my seedlings outside today for the first time, it was about 56 degrees and mostly cloudy. I am going to leave them out overnight and it is suppose to get down to 47 degrees with 90% humidity. I had them under lights all winter but unforunately my lighting set up had to be dismantled until a later date. I have the seedlings in an enclosed small plastic greenhouse.

Do you think they will be ok? How much cold can seedlings tolerate? Thanks for your help.



I keep mine at any temperature above 50; I don’t worry about it getting too warm unless it’s very humid, then they all seem to want to mildew. I think so long as you’re not expecting a freeze you should be fine. The only thing I might warn you about, though, is squirrels and rabbits. Apparently seedlings are very tasty, so make sure your seedlings are safe from those guys.

Hi Fara,

Thanks so much for your reply. I have the seedlings enclosed all around so the little animals cannot get in. Next week we are suppose to get into the mid to upper 30’s at night so now I have to lug them all back in the house. Spring weather is so fickle!


One thing you should be careful of in the spring is too much water. Damping off thrives in the cool, wet weather and will kill your young seedlings if you are not careful.

Thanks Shane, I hardly ever water my seedlings. In the container I keep them an abundance of humidity is always present and the medium I use stays well moist, but I do use a diluted liquid fertilizer and that is really the only time they get watered.

I’ve never worried about temps, so long as they don’t get below freezing by much. If the seedlings are on the ground, a decent blanket or tarp will do for several degrees of frost. I have transferred trays of seedlings to my solar greenhouse where they experience near freezing fairly often and they do fine. And many years I put them outside about now. For sure they will grow a lot faster in a warm house with fluorescent lights, but other than mildew, I’ve not had a problem. Roses are not zinnias, but more like chrysanthemums for hardiness unless you are breeding tea roses. Several degrees of frost will spoil flower buds if not hardened off, but down to 25 we’re fine here (Kansas ), with just a little cover.