Hi, S. I agree your tree should stay outside if it's warm enough where you live, or in an unheated garage if the tree will be subject to temps below 25-28*. Cold-hardiness is largely a genetic trait and in Chinese elm the ability of individual trees to withstand deep chill varies significantly, so better safe than sorry. Also, not all roots are killed by the same low temps. The older, more lignified the roots are, the more resistant to cold they are, so even if a tree will SURVIVE temps as low as 15-20*, much of its fine rootage might be lost, which leaves you essentially with a cutting reluctant to wake up in spring until its energy reserves (that would normally be put to use for branch extension and new foliage) rebuild its frost-killed root system.

Do wait to do the hard pruning until spring, but now you might want to prune back the top. Apically dominant trees tend to want to utilize 2/3 of the energy they make in the top 1/3 of the tree, so we need to be vigilant lest the top branches get too heavy and leave the tree looking unbalanced. I don't like to prune after Aug first, but I did prune the tops of several very promising trees today so they don't lose their twigginess near the top. Your heaviest branches should be on the lowest part of the tree. You control how fat/thin your branches grow by how hard you do/don't prune them. My trees will often have 3-5 well developed branches on the lower part of the tree before I even think about developing a top, which is the easiest part of apically dominant trees to develop because the trees genetic coding dictates that the tree does 90% of the work.

Al

Thank you both very much! All of this info is super helpful. I appreciate it!

How's it faring?

Al

It's doing well! I've kept it outside. I only pruned the length off of the long branches, but I'm nervous to do anything else!

It's so straggly. After doing some research I realize it will take a number of years to get it to look the way I'd like. I'm just not sure where to begin pruning to begin that process. I know you had mentioned pruning back the top... could you explain that to me? Thanks Al!

I can help you with a general plan, but it really wouldn't entail any work being done to the plant, other than helping it remain as healthy as possible until it goes dormant and keeping it viable over winter. Once it goes dormant, maybe you can supply some profile pictures from each side of the tree. You can prune it after it's dormant. Until then, the leaves serve as the plant's food source, so removing them this late in the growth cycle would be counterproductive. I'd plan on repotting it in the spring before buds move, or just at the onset of bud movement, so you'll need to be paying close attention. Where do you live (just a large city near you is fine) and what is your over-wintering strategy?

Al

Ok, I'll wait to prune until it goes dormant. I live in New England about two hours outside of Boston. Autumn is setting in and the low temperatures here at night are mid thirties. We don't have a garage, or unheated indoor space so I'm not really sure where I can put it for the winter season. Would getting a miniature greenhouse to enclose it in, situated on our porch suffice?

That would help, as long as you remember to water it (less than in the growing season). You might still want to bring it in to the coolest room in the house if it gets into the 20s or less. The small, shallow pot allows the roots to freeze. Mine are larger, in bigger pots and I mulch them over winter.

S - you don't want the roots of your elm to get below 28-25*. The reason is, even in very cold areas, say in the middle of a zone 5 tilled field, the 6" soil temp rarely if ever drops below 25*, so being rated hardy to -20* doesn't mean the roots will tolerate -20, because they rarely see root temps below 25* where they naturally occur.

Do you have a friend/parent/sibling ..... that might allow you to bury the plant, pot and all, on the N side of a heated building where it's somewhat protected by wind? That would be a very good spot if you can make sure the roots won't dry out. You'd need to be sure someone tosses a shovel of snow on the pot every month or so. The only concern would be wascawy wabbits and mice/voles.

You could also use an old cooler with the top removed. Put the plant inside of the cooler and then push the open side (top) against a heated building, or over-turn it and set it on top of the p[lant on the N side of a heated building - right on the ground, This will keep wabbits away. Tossing some Ramik mouse/rat bait under the cooler would keep the mice & voles away, too.

It really wants to be BELOW 42* and above about 28* all winter long to come out of its rest in the best shape.

Al

THANK you Al!! Thanks for all the info. I love that I can always count on you to help! The cooler idea is great! I can definitely do that. I appreciate your advice, as always.

I just posted a question in the container gardening forum about identifying some pests I've found in a plant. Would you mind taking a look, Al?