Sunday, March 11, 2007

Repotting of the big maple part 1

I believe that one should only repot when it is necessary. With many trees I feel it's necessary after a several years. Some old collected conifers I don't repot for almost ten years. I learned though that Japanese maples, even wehn they are quite old must be repotted frequently. This old maple is repotted every two years.

Most people repot too early in the year. They 'know' that one has to do it as soon as the buds begin to swell. This is usaulally the case around end of March in my area. While it is possible to repot then it is by no means the best time. I have learned to wait until the buds are pretty far. With some trees I wait until the foliage is almsot out. This is the best time. One can repot most deciduous trees even after that.

Deciduous trees (non-conifers) are repotted here from middle of April to beginning of May. Then come the conifers.

But for trees in a greenhouse everything is about three to four weeks earlier. This year we had the warmest winter ever. My Japanese maples are almost in foliage already, before the middle of March.

So today was the day. I am asked often how in the world I manage to reopt the huge maple. They usually don't believe me when I tell them that I do it in less than one hour all by myself. Yes, it is possible to repot this mosnter without help. But this does not mean that I don't take help when I get it. Like this time.

Fro some people it is also astounding how much of the root ball I remove.


Tom said...

Fantastic work Walter. For this Maple what soil mix did you use? Pure Acadama or your own mix?

Can you give us a little explanation about you soil mix choice

Walter Pall said...


I never use akadama. It is far too expensive and it decomposes and generates very bad soil conditions. This is mainly true in areas where the soil freezes once in a while. In Japan in most areas where they use akadama the soil does not freeze. Here in Germany it is almost poison! Now you know why all the bonsai dealers who try to make some m0oney selling akadama hate me. :-)

In use baked loam 80 % and rough peat 20 %. That's it, nothing else. Baked loam is used in the building industry here in Germany a lot and consequnently very cheap. It does not decompose. In America turface is a similar product.
Instead of baked loam one can also use pumice or similar.


Tom said...

Thanks for your reply Walter. I'm going to see if I can get some baked loam in the UK. I'm sure we probably use similar products to Germany in our building industry.

Helene said...

Hello Walter !
First, I want to congratulate you on your marvellous tree ! And thank you for sharing your knowledge about bonsai on this blog.

I’ve read this text with great interest. I’m looking for a French similar product to your “backed loam” –I’m French ;-)... And I’m a bit wondering about peat. In France, when we want to add vegetal soil in bonsai substratum, we generally use mould and not peat. Please, why do you prefer peat ?

Best regards –and sorry for my poor English

Gaetano said...


Your tree is miraculous.

Wondered if you had any thoughts related to root pruning of acers in autumn. It's common practice with many Japanese maple enthusiasts to root prune at that time. The theory is that roots will grow until the soil is near frost and this will give the tree a head start in Spring. Do you root prune in spring for this very reason?

Walter Pall said...


it is cdertainly NOT common practice to root prune in fall. This is nonsense. Root pruning takes place at repotting in spring.


Gaetano said...

Thanks for you follow up Walter. I am afraid you are mistaken about fall pruning being "nonsense". Here are a few links where knowledgeable growers discuss the practice.

Walter Pall said...

In my climate fall root pruning is utter nonsense. NOBODY would ever do it here.


Marija Hajdic said...

Hi Walter,

soon we will start transplanting from boxes into bonsai pots. Average temperature for March is 10-11 C, so the coldest part of the winter is behind us. Vegetation season will start at end of March, so we hope that repotting can be done now, and that this is not early?! Plan is to transplant on rainy days when we cannot go to collect trees.
Some our trees (mainly phillyreas) have big nebari – it will fill almost whole pot, so little space will be left for roots. Maple roots can be severely cut, but can we do the same thing to Mediterranean species. Our experience is that if we collect Mediterranean species with leaving small branches and leaves on –they mainly survive BUT some branches die out, and all leaves fall of – regularly! Conclusion is that while collecting (and damaging roots), is best to cut off all branches with leaves, and leave only few main branches. Now is our question what will happen with new developed crown if we while repotting, remove big part of fine roots?
So should we wrap those fine roots that can’t fit the pot, and push it inside, or can we cut everything that that exceeds pots size?


Walter Pall said...


the repotting of this maple cannot be compared to collected trees. The maple ALWAYS was a bonsai and is very well settled.
I would try to save as many roots of the collected trees as possible and stuff them into the pot somehow in this phase.


200xth said...

In case you want to see any updates on the tree(s) above since this blog entry, here are the links to each tree(s):

1) Japanese Maple #1

(Still the best bonsai tree in the world in my humble opinion)