Okay to repot... again?

I have another newbie question... sorry... I'm sure you're hating seeing my name already... I hope not...

So I recently ordered a 5yr Chinese Elm. This is my first purchased tree in a while, as I'm making another attempt at growing Bonsai trees. The tree shipped in a VERY compacted soil and was obviously very root-bound. I've always read it's a good idea to repot these trees when you get them so that is what I did. In the past, I had used a mix of Miracle Grow Cactus soil and some of their Orchid mix. I thought the courseness would allow the "fast draining" soil everyone talked about. That is what I used to repot the new tree a week or so ago. I have since been studying, reading, and talking to folks and have realized this soil is a bad choice, especially for trees (may be okay for things like Shefflera?). Since tracking down supplies to make my own bonsai soil is harder than expected, I orded some. It is a Lava rock, Turface, and Pine Bark mixture. Equal amounts of each. I got it yesterday and I can definately see now what a true "fast draining" soil is. So, my question is, now that I have this new soil, is it okay to go ahead and repot the Chinese Elm again? I THINK, I should probably take it out of the current soil, wash the roots off a little, and then put it in the new potting medium. Would this be the right approach?

Normally the general recommendation would be to not repot again, wait until 12 months or more have passed. It has been over a week since it was repotted, short enough that new roots probably have not gotten started or are just starting. Repot now don't stall, or wait and repot in Spring 2016. The general rule is that it takes and entire growing season for roots to recover from repotting. Some species it takes even longer.

Chinese elm is one of the more forgiving species, if you are gentle, and do not trim any more of your roots off, you should be able to "get away" with it. Not the standard recommendation, but Chinese elm should forgive you for it.

You are in Pennsylvania. Because it was repotted in autumn, this elm will need to be protected for winter, kept above 25 F or so. Above 32 F but below 40 F would be ideal. If you wanted to winter this tree outdoors without added heat you never repot in autumn, wait until spring. Chinese elm should be hardy in the ground in your area. The good news is Chinese elm can live in subtropical climates, they do not require a severe cold rest to grow the next year. Other trees like Larch need a definite cold rest, and will fail if kept too warm in winter. Chinese elm does not have that issue.

So in general, do most repotting in Spring if at all possible.

Thanks.

I believe this tree came from a much warmer climate (Florida) so I'm guessing it's not used to the cold/dormant season like we would have here. Even if it is, it's probably used to a 40-50 degree night here and there, and not single digit or teeens (F, not celsius) like it can be here in the winter. I have set up an indoor "grow area" for my plants/trees to help them through the winter. The Elm will hopefully be transiitioned into the outdoors once the last frost has passed in the spring. My current setup indoors gives the trees 16 hours of grow light (I have four 24" T8 single bulb fixtures about 2 inches above the top of the plants (and some morning sun from a south-eastern facing window), steady temps between 68 and 72 degrees. The humidity is the hard part. I have a 4 teir rack with a clear plastic, zip up enclosure (it's made to mimic a greenhouse). The humity has been around 35-40% pretty steadily. I usually leave the front of the "greenhouse" open to allow some airflow in to the plants. I'm sure if I put a pan of water in the bottom and left it closed, the humidity level would increase a little.

I don't think you mentioned how healthy the tree looks, or how dense/large the rootball is. If you would rate it at weak or fair, it might be worth waiting until Spring 2016. Cactus soil is meant to be fast draining, so unless the orchid soil is poor, I would think you would get by fine. If it looks like a pretty strong plant, then as Leo said repot gently and protect.

The roots looked pretty good and knowing it was going to be indoors over the winter, i cut them back a little when I repotted it last week. The tree looks to be fairly healthy and though I've only had it for a little over a week, it hasn't dropped an leaves nor have they lost any of their color. Still dark green. I haven't seen any new growth, but may not for a while. I have just read that root rot can be common with these trees. I soaked the entire pot after I repotted it, to totally saturate the soil. That was just about 1 week ago today. The soil is just now starting to look and feel a little dry to a depth of about 3/4". I'm also using wood skewers to check for moisture depth. I may just keep a close eye on it and leave it in the soil it is in.

I'm sorry to have so many questions that i'm sure are just frustrating to those of you with bigger fish to fry. I'm trying to read and research the best that I can, but there is just so much conflicting information out there.

thank you all again, I appreciate your comments and your knowledge!

The size of the fish is in the eye of the beholder

Suggestion, add a small inexpensive fan (less than $20 from local big box hardware store) to the humidity tent.  That way you don't have to leave it open. You can put it anywhere in the tent, you want enough air movement that thin, grassy leaves would be gently waiving at all times. The breeze can be stronger, trees will take it no problem. When you add the fan, do remember that the frequency of need to water will change, probably need to water twice as often, but this is good. I keep several fans going in my large light garden. Always have a breeze. You could put the fan underneath or on top, and have the deflected breeze keep air circulating throughout the tent. It will help keep fungus and bacterial problems down, and help keep spider mites down. My plant's health improved greatly once I added fans.

Your long day length is a good way to compensate for the lower light intensities of artificial light. Don't worry about photo-periodicity. Only a minority of trees use day length to govern growth cycles. There are exceptions, but I don't think elm is one of the day-length sensitive species. So 16 hour days should be fine.

Well, in fear that my first soil choice (Miracle Gro soil) wouldn't be as fast draining as needed, i went ahead and repotted this elm. It was moved into a pot of lava rock, turface, and pine bark, all equal parts. I think the tree likes as i'm already starting to see some new budding.

Soon you'll be posting pictures- that's great!