Chinese Elm dropping leaves

[AutumnWolf13]

My father got a (8") CE bonsai as a gift around Nov 22nd, and it started dropping leaves. He put it in his ENE facing bay window It's probably around 55 F/13 C -ish, being close to the window and all. It looks to be in a fairly peaty/sandy soil mix. He watered it once a week. I'm going to pick it up tonight and see if I can save it (he really doesn't want it if it is a "fussy" plant, I'll probably get to keep it!).
I'm going to pop it out of the pot and check for root issues, but I'm a newbie myself and not familiar with CE. I'm downloading and printing care sheets, but thought I'd ask.
My questions are:
Will they drop leaves because of cooler temps?
Will they drop leaves due to not enough light?
Will they drop leaves if conditions change too much?
Soil? boons mix? (I have akadama, punmice, lava, turface, haydite, Diatomaceous Earth, Grani-grit& Pine)
If there is root rot should I repot immediately? or try to stabilize it in it's existing soil, and repot after it gains strength?

Thanks in advance.

 

[Oliver Muscio]

My father got a (8") CE bonsai as a gift around Nov 22nd, and it started dropping leaves. He put it in his ENE facing bay window It's probably around 55 F/13 C -ish, being close to the window and all. It looks to be in a fairly peaty/sandy soil mix. He watered it once a week. I'm going to pick it up tonight and see if I can save it (he really doesn't want it if it is a "fussy" plant, I'll probably get to keep it!).
I'm going to pop it out of the pot and check for root issues, but I'm a newbie myself and not familiar with CE. I'm downloading and printing care sheets, but thought I'd ask.
My questions are:
Will they drop leaves because of cooler temps?
Yes, but 55F is not all that cold

Will they drop leaves due to not enough light?
It's likely

Will they drop leaves if conditions change too much?
Probably

Soil? boons mix? (I have akadama, punmice, lava, turface, haydite, Diatomaceous Earth, Grani-grit& Pine)
CE are not all that fussy about soil, so long as it drains well

If there is root rot should I repot immediately? or try to stabilize it in it's existing soil, and repot after it gains strength?
Repot if the soil is water-logged and the roots are rotting, but I doubt this is the case.

Thanks in advance.

,

The main problem is likely that the tree is being kept indoors. In zone 7a it should winter over fine outside, with the tree mulched and protected from drying wind. Also, watering once a week may well be insufficient. Don't water on a schedule, water when it needs it (i.e. when the surface of the soil has dried out, but there is still moisture deeper down in the pot. BTW, my trees (outside) have completely defoliated now.
Oliver

 

[River's Edge]

Chinese Elms lose their leaves normally when entering dormancy. You can pick a cooler spot for it to spend the winter. Between 34 degrees and 45 degrees F would work well.

 

[AutumnWolf13]

Great, Thanks. I think I'm going to keep it. My dad is 87 and suffers from CRS syndrome (Can't Remember Shit). If he put it somewhere other than the window sill, he would forget about it and it would surely die. and I checked with SunCalc, (a really keen on line program that shows the suns track across whatever address you put in and you can change the date too - http://suncalc.net/) and it is probably only getting about 2 1/2 hours of sun right now.
I was hoping it was dormancy...But I'm still going to gently pop it out and check the roots anyhow. I have an unheated garage and a semi heated area (so water pipes don't freeze) that stays 40- 42.

 

[AutumnWolf13]

Gently took it out of the pot and the roots looked/smelled fine. Soil was moist but held no perched water. Popped it back in the pot and watered well. Put it into the semi-heated garage.

 

[rockm]

Great, Thanks. I think I'm going to keep it. My dad is 87 and suffers from CRS syndrome (Can't Remember Shit). If he put it somewhere other than the window sill, he would forget about it and it would surely die. and I checked with SunCalc, (a really keen on line program that shows the suns track across whatever address you put in and you can change the date too - http://suncalc.net/) and it is probably only getting about 2 1/2 hours of sun right now.
I was hoping it was dormancy...But I'm still going to gently pop it out and check the roots anyhow. I have an unheated garage and a semi heated area (so water pipes don't freeze) that stays 40- 42.

40-42 is much too warm for sustaining dormancy--and dormancy is why the tree is most likely dropping leaves. Unheated garage is fine for the tree until spring. Dormant deciduous trees don't need light in the wintertime.

FWIW, dormancy is triggered by light not temperature. Shortening days in the summer and autumn "tell" deciduous trees to begin storing reserves for the winter and to start the process of dropping their leaves. The actual color change and drop are only the end of a months' long process begun in early summer.

A tree's emergence from dormancy in the spring is driven by soil temperature for the most part, which acts as a failsafe for in-ground trees, since it takes more than week long warm snap in February to heat the soil enough to activate growth.

All this goes for temperate zone deciduous bonsai trees too. Optimally, dormant trees should remain as cold as possible for as long as possible--cold being about 35-29 or so. Warmer than that and you get active growth in February, which can be hard to manage since you will have to keep the tree inside for the most part until the danger of frost and freezing has passed. Once a tree's leaf buds begin to open, the tree loses its abilities to withstand freezing winter temperatures.