I have another question that I can't find any answers for. My 3 Chinese elms are, and have always been outdoors all year round, our winters are not terrible but it does drop below freezing every now and then and it snowed a bit a few days ago. The thing is that they do not drop all of their leaves, in fact some are still quite green. Is this a problem?

I noticed you noticed the other thread on this subject. At best, chinese elm are semi-deciduous. We just had some nights colder than -5, dipping into -10. And my elm is also still green.

leatherback wrote:

in my view, you want to have close internodes all along your trunk so you have options of where branches can easily sprout. Once you have the few cm that you will keep in the eventual trunk, sure, let her rip. But I think it would be better to go slow.

www.evergreengardenworks.com/trunks.htm

I think we all know this page. Wondering why I thought what I thought, I looked it up and read:

"When to Make the Trunk Cuts

Before the leaves emerge, the roots are at maximum storage capacity. If you prune then, all that food is going to look for buds to expand, and the growth will be explosive, coarse, and with long internodes. This is exactly what you want if you are only looking to develop the next section of trunk, the portion between branch 1 and branch 2. This will give you the most rapid development. Identify the new leader quickly and protect it. If you are lucky it will be right at the top of the cut that you made.

If you perform this operation after the leaves have hardened (or sooner), you do it when the roots are depleted. They spent a great deal of food (energy) to produce all those new leaves and shoots. This is not conducive to developing a new leader unless you want a weak one with close internodes"

So, it depends. In this case, I 'd say to do that trunk chop early.

Auk wrote:

www.evergreengardenworks.com/trunks.htm

I think we all know this page. Wondering why I thought what I thought, I looked it up and read:
...

Hm.. Isn't that exactly what I said initially?

leatherback wrote:

Depends on what your aim is.

Fast growth you will get if you do this before budswelling. HOwever, this results in large internodes.
Slower growth you get if you do it after the spring growth slows down. You get slow recovery. But also short internodes.

I have a slight preference for late spring (But well before summer equinox!)

leatherback wrote:

Hm.. Isn't that exactly what I said initially?

Yes, but it seems our conclusions are different.

Im thankful for both your input on this subject, I now have a better idea of how the tree will respond if cut at different times of the year.