My sister got a Chinese elm bonsai from a friend who didn't want it -- and my sister couldn't keep it due to their traveling -- so I took it. It was in rough shape, neglected, lots of shriveled leaves, but I thought I'd give it a shot. I grow orchids and have a humidity controlled case I grow them in, so I figured that might help it out. I started watering it with just a little food added, and it responded with a flush of new growth -- some very long new branches with about 12 pars of leaves. I looked online for guidelines, and read that I needed to prune those back to promote branching, so I pruned each new shoot back to about 6 pairs of leaves. From what I read, it should have started a new flush of growth in about 10 days -- but it never really did -- It was really just idle, and some of the leaves started yellowing.

Looking at the pot, it looked like maybe it needed repotting, since the soil seemed very decomposed I decided to give it a try, so picked up some bonsai soil mix, wire, etc. to repot it. The roots were in pretty poor shape but I did my best and it looked reasonably good when I was done.

That was a few months ago. Since then, it just hasn't really done much. It still has leaves, a few new sprigs are there but a lot of the mature leaves are half-yellow.

My guess is that it had needed repotting for some time before I got it, and had root rot to some extent -- is there a way to rejuvenate the roots and get it going again? Any other thoughts or suggestions would be welcome.

TomHudson wrote: I looked online for guidelines, and read that I needed to prune those back to promote branching, so I pruned each new shoot back to about 6 pairs of leaves.

You should not have done that. Pruning is done on healthy trees. Your sick plant needed the leaves to produce energy.

My guess is that it had needed repotting for some time before I got it, and had root rot to some extent

It's possible, but hard to say anything about it without a picture.

Also:
There are so many one time posters that ask the same questions about their sick tree that it's depressing - as is giving the same answer over and over again.
Check the guidelines on this site, under the species guidelines. Use the search function to find similar topics about elms.

Well, I'm sorry to have bothered you -- I was kind of hoping someone could give me a hint about maybe a supplement to help stimulate new root growth, but I can see all the questions here about problem trees so that must be a downer.

So here's a positive update: In the last couple of weeks, the tree has started to put out new growth. Maybe part of this is that I had to replace the main light in the orchid case several weeks ago and went with a multi-spectrum LED unit (it's mounted on a moving track so plants get varying light over a 20-minute period). Or it could be that it just took a while for the tree to start establishing healthy roots.

Whatever the reason, it's now getting new growth in multiple places. I'll let it get really rolling again before doing any pruning, as you suggested.

When it gets a bit further along I'll post some photos.

TomHudson wrote: So here's a positive update: In the last couple of weeks, the tree has started to put out new growth.

That's good news indeed. Good plan to give it time to recover before you start pruning.