Seedling winterizing question

[glass_shark]

Hey folks, I have this pot that I threw a bunch of seeds into, not thinking I would have this much success. Now, I have 4 different kinds of plants in one pot, which is fun, but I'm worried about their winter survivability. I have a silk tree which is the tallest one, that one had taken some damage from the recent cold. Theres also another silk tree seedling thats just popping up, I doubt I could transfer that though. When should I take the tall guy out? Or how should I go about putting these guys away? Thanks again fellas.

 

[Shibui]

Theres also another silk tree seedling thats just popping up, I doubt I could transfer that though.

Why?
Seedlings are primed to grow roots. They can be transplanted at almost any time. Even if the root is damaged in the process, seedlings just grow new roots. Even species that will not usually grow as cuttings can have close to 100% success as cuttings made from seedlings.
The only thing against transplanting your seedlings now will be temperature but, provided you can keep them warm and with enough light to grow until re-established, they should survive transplant.
I'll be interested to hear advice from others who know your local conditions better than I do.

 

[Leo in N E Illinois]

Common names can be misleading, but "silk floss tree" at least in USA most likely is Ceiba speciosa. The Ceiba is native to warmer parts of Argentina, Bolivia, Paraguay, Uruguay and Brazil (thanks to Wikipedia) Which means it most likely will not tolerate more than a few hours of below freezing, more than a few nights per year. In Raleigh, NC, USA this means you must bring the pot indoors any time the temps are predicted to go much below 40 F. You could do the "bring it in, put it back out dance" all winter, as in Raleigh much of the winter will be above 40 F, or if you have a sunny windowsill or an indoor under lights set up, you could grow it indoors for winter.

I would grow the seedlings without repotting until spring or even until next summer. Repotting in autumn or winter will slow growth.

Although everything @Shibui said is true, so if you have a good indoor growing set up, you could repot now. But personally I would wait until spring, unless you had a good under lights set up.

 

[glass_shark]

Common names can be misleading, but "silk floss tree" at least in USA most likely is Ceiba speciosa. The Ceiba is native to warmer parts of Argentina, Bolivia, Paraguay, Uruguay and Brazil (thanks to Wikipedia) Which means it most likely will not tolerate more than a few hours of below freezing, more than a few nights per year. In Raleigh, NC, USA this means you must bring the pot indoors any time the temps are predicted to go much below 40 F. You could do the "bring it in, put it back out dance" all winter, as in Raleigh much of the winter will be above 40 F, or if you have a sunny windowsill or an indoor under lights set up, you could grow it indoors for winter.

I would grow the seedlings without repotting until spring or even until next summer. Repotting in autumn or winter will slow growth.

Although everything @Shibui said is true, so if you have a good indoor growing set up, you could repot now. But personally I would wait until spring, unless you had a good under lights set up.

I mainly just want to get the not-elm
not-maple seedling, I don't think it likes the cold. Everyone else in the pot I'm fine with keeping outside, my indoor setup is pretty far along as well so it should survive the winter if nothing else. Everything else in there is maples and elms which I will probably keep outside most of the winter at least.

 

[Shibui]

Everything else in there is maples and elms which I will probably keep outside most of the winter at least.

This was not made clear in the original post but makes a big difference to the advice.
You may be able to nurture the other seedlings indoors along with the silk floss trees as seedlings seem to cope with less than ideal conditions better than older trees.
Ditto for dormancy. Most species can miss one winter without too much trouble so if you are reluctant to prick out the frost tender species you could try to winter the entire pot indoors. This carries a small risk.
You could try to prick out the silk floss seedlings. I suspect the new emerging seedling will not even miss a beat if it comes indoors to good conditions but there is some small risk again.
You could elect to just leave the whole pot outdoors and accept the almost certain loss of the silk floss seedlings and try again next spring.

Not sure there is any other alternatives. You (unknowingly) decided to create the situation so now you need to make the decision to deal with it.

 

[leatherback]

Do you have a spot just above freezing? Then you can just keep the whole pot there for winter, push all plants into dormancy, without frost-damaging the albizia. Repot into individual pots in spring.

 

[Leo in N E Illinois]

This thread highlights why in general when planting seed, one only puts a single species in a single pot. Mixing species leads to issues when one species needs different conditions than others.

But to help with the current issue, @leatherback is right, just winter the entire pot, indoors under lights, the hardy seedlings will survive, and in spring, you can separate the seedlings transplanting them to individual or to groups of single species pots.