How cold can seeds get

Hi all,

Just a quick question, I am new to rose hybridizing and just wanted to know how much cold can seeds be expose to. I just planted some seeds in soil and play sand and placed them out in a small cold frame that I build out of cinder blocks and wood and tonight it is suppose to get down to 29 degrees. They are in the sun all day and it gets very hot in there, it is now 86 degrees and 46 outside. Should I bring them in or leave them? Thanks for your help.

You need to put them where they don’t get so much heat during the day. They will handle the 29 degree air temperature just fine. They’ll germinate a lot better with normal air temperature variations between 50 and 30 or 35 degrees Fahrenheit. Remember that the medium they’re planted in won’t be going down to that temperature unless it’s exposed to it for a long time–the mass of the container will keep the temperature up, so the occasional low temperature will do no harm. High temperatures will generally stop or greatly decrease germination.


Whoahhhh, anything much over 75F will seriously limit germination, so try to avoid it getting that hot. A light frost won’t do any damage, but anything colder than 28 or 29 should be avoided.

Thanks for advice. I have to shade the coldframe, it does get too warm, would like to move it but no space available now. For now I will bring my seed trays in and put them in a back room I have, if I close the door and the heat vents to the room I can get it down to at least 55 deg. to 65. Last night it did get down to 28 but the wind chill made it feel like 19, is this the temperature we go with when maintaining temperatures for the seeds?