Removing all the old soil or not when repotting elms?

[Bonsai Nut]

The issue is that Chinese Elms are illegal to buy/sell/own where I live, due to Dutch Elm Disease.

Interestingly, Dutch elm disease ravaged our native American elms and almost wiped them out... but "almost" meant that some old-growth American elms survived because they had rare mutations that made them resistant to the disease.

There are now a fair number of American elm cultivars that are partially or completely resistant to the disease, and work is being done to re-establish them throughout the country.

 

[Ingvill]

Thanks a lot, everyone
I'm sure us newbies ask you guys the same questions over and over, and you patiently answer us again and again, lol.

I spent all of yesterday reading up on the disease and I've contacted the proper authorities to get some more information as well.
My two little trees should not, in theory, pose any threat to my surroundings.
The beetle does prefer larger & older trees and can only fly a relatively short distance.
My worry is not that my two elms could die to the disease, it's that my elms could infect elms in nature.

I will certainly not be buying any more trees labelled Zelkova.

 

[Tieball]

My Zelkova came out of the ground in 2017 at bud swell time and I moved to a growing box. I cleaned out all of the old ground soil. Bare roots only. Pruned back some roots. Put it in the box. It grew very well, very healthy, very green, and put out plenty of shoots in 2017 and I expect the same for 2018.

But.....reading back over this post...I see you may have concluded Chinese Elm rather than Zelkova. Anyway....I thought my bare rooting experience could be helpful.

 

[Ingvill]

Thank you Tieball, yes my elms are no longer Zelkovas lol.
But still it's very reassuring to see that bare rooting seems to be a good way to go with elms/decidious trees in general
It seems most store purchased trees comes in these horrible soils, so I'm very happy to know I can get rid of it all now.

 

[Tieball]

Interestingly, Dutch elm disease ravaged our native American elms and almost wiped them out... but "almost" meant that some old-growth American elms survived because they had rare mutations that made them resistant to the disease.

There are now a fair number of American elm cultivars that are partially or completely resistant to the disease, and work is being done to re-establish them throughout the country.

Nice. I have several American Elms growing very healthy on my property. And several mighty smaller size trees in my growing ground area. All doing very well.

 

[Tieball]

I had Chinese Elms....had....they did not like my winters and living outdoors with all the other trees. So.....just no more Chinese Elms for me. Trees I have must live outdoors, in all the conditions, year round.

 

[Ingvill]

@Tieball ;

I read somewhere the following infomation, but I have no idea if it's true or not;
- Chinese Elms have different winter hardyness depending on where in China they originally originate from.
- Some are quite winter hardy (from colder parts of China) and some are quite sensitive (from warmer parts of China).
- Since we rarely know where our trees can be traced back to, we should treat all Chinese Elms as trees needing some winter protection.

To me, this sounds a bit like "Donald Duck science", lol.
But if it is in fact true, it could explain why people have such different experiences with this elm's winter hardyness.

 

[M. Frary]

I had Chinese Elms....had....they did not like my winters and living outdoors with all the other trees. So.....just no more Chinese Elms for me. Trees I have must live outdoors, in all the conditions, year round.

I have 2 Chinese elms that made it through winter last year and will more than likely be alive come spring. They're made from cuttings of a cork bark Chinese elm. That tree sadly died in a vicious assault from the V.C. 3 winters ago. I also had a seiju that could live outside here. It unfortunately met the same fate.
The thicker bark Chinese elms are more cold hardy than others. Exfoliating bark down to smoother bark trees aren't so much.
I live in zone 4. We haven't had it yet,but it gets down to 20 below zero or more here.
With the global warming I'll be growing Japanese maples too. I'm getting a small one to try next winter.

 

[Anthony]

@Ingvill ,

our elms were purchased in 1993 and 1996, they were Mallsai from Soho, London, Mr. Mings.
We also have 1980 from the US ---- catlin

There were 5 or 6 different types. The source was Red Sun Bonsai outside of of London.
We visited the nursery and found them to be outside in November/ December with a
translucent plastic covering over the lot of trees. Possibly to prevent Frost damage ?

From there we found out that they were from Holland and had come from South China [ zone 9 ]
and were shipped in the containers x months on sea.
The soil was whatever they were growing in the open fields in China.
More or less a clay type with stones.

We cannot import conifers and other trees must be barerooted. So we washed them and then
treated them for nematodes and the English Plant Quarantine folk inspected them for the
cost of 20 pounds.

Of the types, one proved to be a monster at growing.
We use root cuttings to propagate and one cutting in a 1/3 US 55 gallon black plastic barrel,
with a coarse soil mix shot up to 8 cm in 6 months.

So I would advise do some root cuttings when the weather is with you.

Anyhow, they sleep from Christmas until February 15th and are all alive today.

I mentioned Zelkova Sinica since that is how they were listed in the 80's [ and in Italy
as well ] to be imported.
The mallsai are mostly like to be Southern Chinese Elms, so you would have to test
the root cuttings by growing them outdoors for the year.

Our new root cuttings are just about to put out shoots.
Roots are often more interesting than the top of the tree cuttings.

They grow easily indoors, but they need to be rested, or after 4 years, like maples,
without a winter's rest may just fade or die suddenly.
Good Day
Anthony

Southern Chiinese elm ------- the 6 month special

 

[Ingvill]

Very interesting reading, thank you so much for sharing, I always learn something new, @Anthony and @M. Frary