How to proceed with this Chinese elm?

[Jolly Green Ground Sloth]

I took this branch-tip cutting from a Chinese elm on a university campus in late May 2023. It rooted, but didn't start pushing new growth till around the first of October, when, after an almost continuously cloudy late summer, we had a string of bright sunny days and temperatures above 80 F.

This is how it looked on September 28 (it's just starting to form buds):



This is how it looked on October 10:



After a week or so of sunny days, the forecast suddenly turned cold. We had our first nighttime frost around mid-October. At this point, when I brought all my cacti and succulents inside to live in a grow tent for the winter, I decided to bring in the Chinese elm as well.

I've read threads here and elsewhere about the pros and cons of keeping Chinese elms inside. My thinking was that, while it's probably better to let them live outside, people do successfully keep them inside, meaning it can be done. And I was worried that this particular cutting would've spent all its energy pushing new growth just in time for it to die off with the cold weather and that it wouldn't have any energy left for spring. Also, I'd taken similarly sized cuttings from that same Chinese elm landscape tree in 2022, and of the half-dozen cuttings that rooted, all of them died over winter. So, I thought it would be safest to bring this one inside for just this one winter. After this, it will live outside 100% of the time.

It seems to like living in the grow tent. This is how it looked on October 18, after a week indoors:



And here's how it looked a few days ago on December 11 (after several cutdowns to keep it from growing up past the grow lights (it's still living in the tent; I just took it outside to take the picture)):



My questions concern repotting and reacclimating the tree to the outdoors in spring.

The tree needs to be repotted. It's got roots coming out the drain hole. But it's obviously not going to go thru winter dormancy living in the grow tent, so I'm probably going to have to repot it while it's in full-leaf. I was wondering about the timing.

Would it be better to repot the tree this winter and let it recover in the grow tent before moving outside in the spring? Or would it be better to move it outside first and then repot it during later spring or summer? Or would it be better to wait a full year? (I don't want to wait a year, because I'm worried the tiny pot will restrict the growth.)

Also, do I need to do anything to prepare the tree for moving outside? It's currently on a 16-on / 8-off lighting schedule. Should I start reducing the hours of light to match the actual daylight as spring approaches?

Can I move the tree directly outside? Or do I need to start putting it out for a few hours a day and gradually increase its exposure to sunlight?

Any advice would be appreciated.

 

[Mikecheck123]

Why do you think it needs to be repotted?

It doesn't. Just leave it alone until it's warm again.

 

[Deep Sea Diver]

After a week or so of sunny days, the forecast suddenly turned cold. We had our first nighttime frost around mid-October. At this point, when I brought all my cacti and succulents inside to live in a grow tent for the winter, I decided to bring in the Chinese elm as well.

I've read threads here and elsewhere about the pros and cons of keeping Chinese elms inside. My thinking was that, while it's probably better to let them live outside, people do successfully keep them inside, meaning it can be done. And I was worried that this particular cutting would've spent all its energy pushing new growth just in time for it to die off with the cold weather and that it wouldn't have any energy left for spring.

Some really good questions!
Likely a good move. Putting in a grow tent for a year is ok. Chinese Elms are pretty hardy when stronger and older. Rated for zone 5-9 so in the pot that’s zone 6 for the elm, if mulched in and otherwise protected. It’s possible to winter the tree inside in the future until its strong and older… or ad infinitum…Lots of folks do this…. (but if wintered over, the tree must go through the steps needed to achieve dormancy.)

My questions concern repotting and reacclimating the tree to the outdoors in spring.

The tree will need an uppot not a repot. “A slip pot“. No root reduction this time. Be sure to match the media type used originally when this is done. Would suggest moving the tree into a bigger Tokoname Grow Pot. (The pot type in use is normal terracotta. These pot are fragile, suck water out of the media and aren’t freeze proof, Tokoname pots are stronger, suck little water and are can freeze.). This pot will allow the roots to spread out the the tree grow stronger.

The tree needs to be repotted. It's got roots coming out the drain hole. But it's obviously not going to go thru winter dormancy living in the grow tent, so I'm probably going to have to repot it while it's in full-leaf. I was wondering about the timing.

Being that the tree is in a grow tent, likely the slip pot can be done anytime this winter.

Can I move the tree directly outside? Or do I need to start putting it out for a few hours a day and gradually increase its exposure to sunlight?

The tree will need to be hardened off. Three environmental factors need to be considered when doing this as the tree is in a grow tent.
1. Temperature hardening
2. Light duration match
3. Acclimation to the outside humidity, as grow tents tend to have high humidity.

This isn’t all that complex. Here’s the formal routine. (We follow this routine with hardening off azalea etc cuttings..)

Normally one puts the tree outside in part sun for a few hours a day for about a week, increasing the amount of sun and hours a bit over the week. Next week increase stay time each day or two until same as daylength …and by the end of the second week the tree will be acclimated… given no cold snaps.

In this case the tree likely needs to be moved out of the tent a week or two ahead of time into an intermediate, somewhat humid area, like a kitchen. Easing it in near a window over time will help acclimate the tree. My better half would be ok with this, but…..

Then again one could just bring the tree right outside…. …and some would!

Any advice would be appreciated.

Hope this helps.

cheers
DSD sends

 

[Shibui]

Chinese elms can grow in cool, temperate or tropical climates. In tropical areas they never lose leaves but growers have found that they can root prune and repot any time of year so don't worry too much about repot timing. It should cope.
Just because roots are showing at the drain hole does not mean it is pot bound or needs repotting. The first place roots go is to the edges of the pot then down and to the drain holes. They show up there well before the pot is full of roots. For a better gauge, press down on the soil. If it is packed hard it needs repotting but if the soil can be compressed with a finger there's still plenty of spaces for roots.
Change of light hours should not worry the tree. Sudden changes in sun intensity and temp can cause problems so make the transition to outdoors gradual - a few hours at a time building up to fully outdoors over a week or so and to full sun after 2 weeks.

 

[Tieball]

Nice healthy looking growth. Keep up the excellent care.

 

[Jolly Green Ground Sloth]

The tree will need an uppot not a repot. “A slip pot“. No root reduction this time. Be sure to match the media type used originally when this is done. Would suggest moving the tree into a bigger Tokoname Grow Pot. (The pot type in use is normal terracotta. These pot are fragile, suck water out of the media and aren’t freeze proof, Tokoname pots are stronger, suck little water and are can freeze.). This pot will allow the roots to spread out the the tree grow stronger.

Being that the tree is in a grow tent, likely the slip pot can be done anytime this winter.

Thanks for the detailed reply.

I was hoping to get the tree into some better draining soil. But slip potting it sounds like a decent compromise. It's growing well enough in that soil for now, so it can probably tolerate it till spring '25.

I do plan to phase out all of my terra cotta pots this spring. I bought a batch of those Tie Pots from the Stone Lantern website--they may just be overpriced colanders, but they seem pretty sturdy and are supposedly UV resistant, so I didn't mind paying extra for them. I'll pot the elm in one of those maybe around the beginning of February without molesting the roots.

 

[Jolly Green Ground Sloth]

Change of light hours should not worry the tree. Sudden changes in sun intensity and temp can cause problems so make the transition to outdoors gradual - a few hours at a time building up to fully outdoors over a week or so and to full sun after 2 weeks.

That's good to know. So, I'll just treat it the same way I do my succulents: start putting it out for a few hours on warm spring days and gradually increase its exposure.