Columbine seedlings and cold weather

Question

I live in Colorado, on the front range. I bought four columbine plants in July 2015 at a local hardware store. They all four seemed to grow during the summer but failed to return this last spring. So I bought four more in May of 2016 and planted them again. I also picked up a packet of seeds at the same time. I refilled 2 empty 6-pack flower containers with starter soil and planted the seeds. The four adult plants I bought grew well during the summer and fall. I kept them moist, but not soaking wet during the summer. I collected their seed pods after blooming then deadhead the flower stems. I took the seeds I collected and placed them in starter soil and also put them in an old 6-pack container in August. I wet the soil then put the whole 6-pack in the freezer for a little over a month. I was told to do that to help the seeds germinate.

Okay, so now it’s late November. I now have 6 good sized plants (about 10 inches tall, good stems with several leaves) from the first packet of seeds I planted in July. I transplanted them in September from the 6-packs into 6-inch pots when they outgrew the smaller space. The new seeds that I collected, froze and thawed are now about 1 1/2 inches tall and still in the 6-pack container. They were all originally grown outside until our first snow last week, when I brought them into my kitchen. I left the 4 original (planted, adult) outdoor plants in the snow and hopefully they will be okay. They still had green leaves on when it snowed. Now those are starting to wilt and die.

After all that background, my question is, what do I do with the 6 original plants I grew from seed? How do I know how big they need to be to withstand the colder weather? How do I accustom them to the cold to get them to go dormant? Should I put them outside again, but not in the snowy areas (like a porch)? Also, at what point do I put the newer seedlings outside? They are so small still and I think the cold will just kill them completely. I know columbines can grow in Colorado because it’s the state flower. Any help you can offer will be great.

Thank you so very much for your assistance.
Kurtis

Answer 1

Columbines are winter hardy in gardening zones 3 to 8, so adult plants in the ground should be okay anywhere in Colorado except high mountain areas. If they keep dying every winter, you could try covering them:
https://www.gardeningknowhow.com/plant-problems/environmental/protecting-plants-winter.htm

Plants in containers and young plants are less cold-hardy and will likely be killed by the cold if left outdoors. I recommend keeping all the seedlings indoors until spring, then planting them outdoors after your last frost date.
Also, columbines are perennial but short-lived, averaging 2 to 3 years, so it’s a good idea to continue collecting the seeds to replace them as you have done.