First winter for a Chinese Elm started from seed.

Hello all, this is my first post and first time joining a Bonsai forum - until now reading forums as a guest has provided all the information I've needed.
So anyway, I'm joining to ask about what precautions should be taken for a Chinese elm's first winter.

I am supposedly in zone 6, Murfreesboro, TN 37130.

The tree was started from a seedling late spring/early summer and has been kept on my East Facing third floor balcony.
It gets sun from morning till around Noon which is not as much as I'd like but its the best I can provide given that I cant just make my balcony south facing.
It is growing in what I believe is a half gallon pot - the soil is a mix of ADA Aquasoil Amazonia, Sand, and Peat moss (Edit: Woops, perlite is in there too!).
Aquasoil is an aquarium substrate that is fired clay with some inorganic fertilizer in the form of NH4(ammonium), as well as plenty of trace elements, and a high CEC, (Cation Exchange Capacity) I only used it because I had some left from my Planted Aquariums - it is after all, pretty expensive.

So one of the trees is much taller than the others, it was also the seed that sprouted the quickest - good genetics?
Downside to all of the trees though is some asymmetrical leaf placement - The leaves all face one direction, and the tree is leaning in said direction, I've been rotating the tree but it only serves to keep the stem upright.

To the final questions I suppose.

We do get temperatures below 30 at night during winter, and occasionally temperatures, in the 5-15 Fahrenheit range.
What I've read so far is that the tree should be fine, even in those cold temperatures, provided that it isn't several days of extreme cold, as in, one night should be fine if it warms back up in the day.
I understand Ulmus Parvifolia has fleshy roots that aren't excited about being frozen.


So, should I bring this tree in on very cold nights, and if so, what temperatures would dictate me to do so?
What kind of insulation, if any, do you recommend placing around the pot?

Thanks for the help!

Well here is the tallest one, viewed from the side the leaves all mainly face.

Maybe my post was too lengthy?

Summary - Should I bring this tree in on very cold nights, and if so, what temperatures would dictate me to do so?
What kind of insulation, if any, do you recommend placing around the pot for winter?
Or should I bring it in?

I assume I shouldn't bring it in as it will be too warm, too dry, and too dark.

Leave it outside. Chinese elms can take Tennessee winters, and it will be warmer on the third floor, too.

Your seedling is in need of its first trunk chop. You might consider it after the leaves have fallen.

Ok yea I figured the tree would be fine outside I'm more wondering about if I should mulch around the pot.
Ive been considering making a large wood box to place the pot in to fill with mulch.
I think the tree needs to be in a bigger pit anyway if I want a thicker trunk anytime soon, any advice on when that would be a good idea? Spring?

JimLewis wrote:
Your seedling is in need of its first trunk chop. You might consider it after the leaves have fallen.

I'm curious Jim, why would you suggest a trunk chop that would only end up slowing the growth of this little guy?? Just wondering.

Well, for the same reason you prune any plant -- because the only way it wants to grow is UP. He will want to encourage branching. It is only through branches that you get better trunks. Chopping that teensie stem will encourage all the buds at leaf junctures below it to sprout side buds.

I'm not going to be doing a trunk chop - I haven't read anything that would encourage me to do that yet - the tree isn't even a year old.
But... I am still wondering if I should build a box to mulch around the pot.
Anybody?

After the winter time, you should leave it grow freely in a corner of your garden or in a big container with a regular fertilization, in 2 or 3 years, the diameter of its trunk wille be between 1,5 and 2cm. Then you will be able to do the trunk chop to work on its branches.