The eternal Mugo dilemma

[Julio-Rufo]

Since I started doing bonsai in the early 2000s, I have always repoted my trees late winter or early spring, apart from some specific species like Olive and wild Olive.

As you all know, specifically about Mugo pines (and other species) there are two streams when it’s about repoting them:

-Late winter/early spring repot: right when the buds start to move and show some green tones. This timing is the the one recommended by professionals like Ryan Neil.

-Summer: once they have hardened. This timing is preferred and recommended by Vance Wood among others.

These two references come from bonsai artists based in United States my question is now directed to European practitioners (I am based in Basel, Switzerland):

When do you repot your Mugo pines especially when certain root reduction is required?

It is curious to see than even when some of the best Mugo pines in bonsai are in Europe, the amount and quality of information about them is not so good here.

Julio

 

[Kadebe]

I have a mugo that needs a repot this year. And after reading a lot of advice, I'll follow the guide of Harry Harrington

Pinus mugo/ Mugo Pine Bonsai Indepth – Bonsai4Me

www.bonsai4me.com

The reason is that his climate in England is almost the same as here in Belgium.

 

[Julio-Rufo]

I have a mugo that needs a repot this year. And after reading a lot of advice, I'll follow the guide of Harry Harrington

Pinus mugo/ Mugo Pine Bonsai Indepth – Bonsai4Me

www.bonsai4me.com

The reason is that his climate in England is almost the same as here in Belgium.

Cool, thanks for this!

 

[Potawatomi13]

Walter Pall has several Yamadori.

 

[Wires_Guy_wires]

I do spring repots for mugo, because they die in summer if I do so.

My reasoning is plain and simple; I asked myself when does the soil on the Alps - at the level where mugo's roots are - move naturally?
From what my Swiss friends an family told me, it's mostly spring when there's a difference between thawed and frozen layers, when ice cracked rocks come loose.

Since mugo wakes up before the snow has fully disappeared and can actually grow through snow itself, this means it has an auxin trigger somewhere in early spring. Auxin triggers shoot growth and root growth. The soil movement in spring is by far the largest and most damaging. So 1+1=2.
I repot them before anything starts being active. If you wait until bud elongation, you may have missed the initial auxin flush.

So spring it is. And it seems to work. I have a list somewhere, but I can't seem to find it so I'm doing this from the top of my head:
Summer repot total: 4. Summer repot deaths: 4.
Spring repot total: 6. Spring repot deaths: 0.

 

[Julio-Rufo]

I do spring repots for mugo, because they die in summer if I do so.

My reasoning is plain and simple; I asked myself when does the soil on the Alps - at the level where mugo's roots are - move naturally?
From what my Swiss friends an family told me, it's mostly spring when there's a difference between thawed and frozen layers, when ice cracked rocks come loose.

Since mugo wakes up before the snow has fully disappeared and can actually grow through snow itself, this means it has an auxin trigger somewhere in early spring. Auxin triggers shoot growth and root growth. The soil movement in spring is by far the largest and most damaging. So 1+1=2.
I repot them before anything starts being active. If you wait until bud elongation, you may have missed the initial auxin flush.

So spring it is. And it seems to work. I have a list somewhere, but I can't seem to find it so I'm doing this from the top of my head:
Summer repot total: 4. Summer repot deaths: 4.
Spring repot total: 6. Spring repot deaths: 0.

Thanks, that is helpful. So you do not wait at all until you see anything changing colour or slightly moving, at all?

 

[Wires_Guy_wires]

I wait until I don't see any more frost predictions. That's usually my timing to repot European pines.
But there's a "gut feeling" at play here too. I've only been wrong about this twice in 20 years or so.

 

[Julio-Rufo]

I wait until I don't see any more frost predictions. That's usually my timing to repot European pines.
But there's a "gut feeling" at play here too. I've only been wrong about this twice in 20 years or so.

Gut!

 

[Colorado]

I only have one mugo, but last year I repotted it in the spring and it didn’t skip a beat. For whatever that is worth.

 

[sorce]

I think where you are located is the largest determining factor.

Other factors include winterizing method, trimming timing, and because Vance uses baskets, container.

I'd bet these factors will line up the same for Spring Success and Summer Success, because these people both exist. And many rather observant folks report all deaths in the other time, on both sides.

Folks without these other things lining up are killing them.

Sorce

 

[BonjourBonsai]

Last summer I repotted about 10 mugos from a box store. 4 were large specimens with smallish needles about 1 inch or less. They were probably a dearf variety. The others had longer needles but we're smaller trees. I think they were the common pinus mugo. The bigger ones all died. The smaller ones all lived except for 1. I followed the "saw off half the root ball method" for all of them. I have one large dwarf tree that I did not repot last summer. I'm going to repot it this weekend. I hope it likes the spring!

 

[BonjourBonsai]

First one is a big one that died. Next photos are the same tree that is fine so far.

 

[Paradox]

I have repotted both in spring and in summer
Overall I have had better success and better response from the trees that I repotted in spring
I have had summer repots die and never had one die in when repotted in spring

 

[M. Frary]

Summer

 

[penumbra]

Almost all I re-pot in summer is my tropicals, though there are a few plants like cotoneaster that don't seem to mind it.
I just potted 15 small Mugo pine about a month ago and so far they look great. That is early in my climate but they are not cultivars, just the original zone 2 mountain pine from seed.

But Sorce makes a great point, there are people in both groups, so you need to decide what group you are in.

 

[TomB]

I have a mugo that needs a repot this year. And after reading a lot of advice, I'll follow the guide of Harry Harrington

Pinus mugo/ Mugo Pine Bonsai Indepth – Bonsai4Me

www.bonsai4me.com

The reason is that his climate in England is almost the same as here in Belgium.

This is worth reading too https://www.kaizenbonsai.com/blog/2018/08/learning-to-speak-bonsai-mugo-pine/

I don't have any Mugos at present, but the last one I had I repotted in August, and it worked well.

 

[Leo in N E Illinois]

Most trees have more than one season that they can be repotted in. If you understand your tree's horticulture needs, and are careful with your AFTERCARE, one can repot at various times of the year. AFTER CARE is key.

Spring is the obvious choice, aftercare usually requires protection from frosts and avoiding drought.

Middle to late summer is another common choice, protection from intense sun afterward, and possibly protection from extreme cold the following winter is part of the after care.

For some species like Chaenomeles and Diospyros, autumn repotting is recommended, for Chaenomeles to avoid root nematodes, for Diospyros it seems to be the time when the losses are reduced. With Diospyros (persimmons) avoid root pruning as much as possible. Avoid repotting as much as possible. See Julien Adam's website for recommendations slightly different than mine. I have only worked with kaki and virginiana, he has worked with D. rhombifolia.

Point is: Spring, Summer, and Autumn are possible repotting seasons if one understands what adaptations they have to make to aftercare. Some seasons are better than others, by and large, most people find "Spring" the "no brainer" easiest season to repot in. Myself, living in a unique microclimate close to Lake Michigan, I find FOR MYSELF, late summer is a very easy season to repot trees in, especially conifers, but deciduous too.

Your local climate matters. If you live in TEXAS or the desert Southwest DO NOT try to repot in summer. Here, meaning Texas or desert southwest, if winter is mild enough, autumn or winter or late winter repotting is more appropriate.

Local climate is everything.

 

[Julio-Rufo]

This year I have decided to repot Mugo in late winter, and the result has been quite good so far. It was performed about two months.
The tree roots were reduced quite a lot and repoted into its first bonsai pot, the angle is not the desired but I opted to not reduce the roots more in order to keep it healthy.

 

[BonjourBonsai]

Looking good!