Repotting in late autumn

I am curious as to peoples thoughts on when to repot. The general advice given is to repot in spring as buds swell.

I was listening to a talk recently that advised late repotting around November in the UK. Given adequate protection this will be beneficial to the tree. The roots will continue to grow over the winter period and will allow earlier fertilizing.

What species are we talking about?

Sounds like BS to me.
In order for roots to keep growing, the tree can't be allowed to go dormant.

For species that need dormancy, not allowing dormancy is a bad idea that could and probably will weaken the tree which is not beneficial. Weak trees dont grow well.

Do that too many years in a row and the tree will die.

There was no species specific advice given with this technique unfortunately. I was under the assumption that trees don't go completely dormant during these months and that roots continue to grow. The theory was also backed up in another talk that I stumbled across online.


unfortunately I cannot remember exactly where it's mentioned but it's an interesting talk

I remember a post somewhere here where somebody said they listened to podcast or something and the theory was that roots during dormancy continue to grow.
I’m in the same camp as @Paradox but just saying there was a discussion around this topic on this forum somewhere

I have not used the technique myself. The speaker of the talk is a well respected arborist, the second talk I believe worked for the UN as a toxicologist. I cannot defend the theory myself, I would just like to hear others opinions.

Adamski77 said:

I remember a post somewhere here where somebody said they listened to podcast or something and the theory was that roots during dormancy continue to grow.
I’m in the same camp as @Paradox but just saying there was a discussion around this topic on this forum somewhere

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Would it be possible to find a link to the thread? I did try to have a look to see if a similar thread had been posted before

I was almost right... sorry if I mislead anybody.... here is the link and for full clarification this was summer dormancy and not winter dormancy

Adamski77 said:

I was almost right... sorry if I mislead anybody.... here is the link and for full clarification this was summer dormancy and not winter dormancy

Too late for procumbens UPpot?

Going into summer? Tree is tied to bench in case of wind. I have a bigger pot that is too heavy to blow over. Thus the time question.

www.bonsainut.com

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Thank you for the link

This seems a better link for summer repotting. Let me know if there are any links for autumn/ early winter potting

Late summer CAN be done, doesn't mean it SHOULD be done. Early spring is optimal for most all temperate species. That's the season when temperate zone trees are primed for their most active growth. Summer can be an ALTERNATIVE season but it also shortens the time for root recovery even though roots can continue to grow up until the soil reaches 40 or so. Spring repotting take more advantage of that time than summer as roots have longer to grow undisturbed.

Late summer repotted trees will benefit from freeze free storage over the winter as well.

Ive often bought trees in winter and repotted them without much issues, mainly hornbeams. you can look up the bareroot season in the UK. Look up Harry harringtons website, he also has success collecting in autumn, winter for some species. I believe Leatherback on here also repots at various times.
you can buy cheap nursery stock and see for yourself. when you ask first, most advice will be given with a cautious approach. Ive never asked for advice on such stuff, I just research and do, and learn.
This is in regards to deciduous trees.
If you check out Graham potters channel on youtube, he has some success with conifers repotting in the summer months.

BobbyLane said:

Ive often bought trees in winter and repotted them without much issues, mainly hornbeams. you can look up the bareroot season in the UK. Look up Harry harringtons website, he also has success collecting in autumn, winter for some species. I believe Leatherback on here also repots at various times.
you can buy cheap nursery stock and see for yourself. when you ask first, most advice will be given with a cautious approach. Ive never asked for advice on such stuff, I just research and do, and learn.
This is in regards to deciduous trees.
If you check out Graham potters channel on youtube, he has some success with conifers repotting in the summer months.

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Yes, the UK nursery lifting season was one of the examples given in the talk. The talk was by Amelia Williams from Swindon bonsai society. I do plan to experiment on stock at some point, to see the difference between half potted in spring and half later in the year but I will only be able to test young trees of a similar age as it would be difficult to get a group of similar mature trees.

rockm said:

Late summer CAN be done, doesn't mean it SHOULD be done. Early spring is optimal for most all temperate species. That's the season when temperate zone trees are primed for their most active growth. Summer can be an ALTERNATIVE season but it also shortens the time for root recovery even though roots can continue to grow up until the soil reaches 40 or so. Spring repotting take more advantage of that time than summer as roots have longer to grow undisturbed.

Late summer repotted trees will benefit from freeze free storage over the winter as well.

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I thought the idea was to extend the time the roots have to recover not shorten it? They will have a period in winter and also the push of growth in spring?

Thank you both for the feedback.

James89 said:

Yes, the UK nursery lifting season was one of the examples given in the talk. The talk was by Amelia Williams from Swindon bonsai society. I do plan to experiment on stock at some point, to see the difference between half potted in spring and half later in the year but I will only be able to test young trees of a similar age as it would be difficult to get a group of similar mature trees.

I thought the idea was to extend the time the roots have to recover not shorten it? They will have a period in winter and also the push of growth in spring?

Thank you both for the feedback.

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Do the math--sever roots in spring--6 months of regeneration/nutrient storage time. Maximizes root activity in the fall--Sever roots in the late summer you will get possibly three months of growth before dormancy if you're lucky... That timing also removes resources accumulated during the spring summer. Root growth slows and/or ceases when soil temps drop below 35 or so. With fall root pruning you're betting on a mild winter--which might be the case in the U.K.--most of the time, but in most of North America, we get substantially low wintertime temperatures.

The fall repotting stuff comes up all the time, but it's simply a mostly lesser alternative to springtime repotting. It's not some new discovery.

What issues with Spring repotting are you trying to overcome with late-autumn repotting?

Definitely not new or a special 'technique'
gardeners/landscapers have been transplanting trees during the bareroot period for decades. I took this and applied it to trees in pots with not much issues. I do the spring stuff too. however, our springs are so unpredictable now, you can never know what to expect afterwards. A lot of folk tend to disregard constantly changing weather conditions, when dishing out the same advice.

Not a new technique, it’s done a lot depending on the climate and the hobbyists inclination (and numbers of trees onboard!)

The key, as mentioned above, is that one has to protect the tree during winter In such a way as the roots don’t freeze (more protection than usual wintering over) don’t get diseased and the upper hamper doesn’t get the diseases that often afflict trees being protected…. So plenty of ventilation.…. followed by a proper transition back into the open.

It can be a lot of work, or very little depending on the climate. I wouldn’t toss the dice on our best trees.

btw I noticed last winter that people are punching out an awful lot of bonsai videos nowadays….

Some good, lots not, a few exceptional. I try to stick to the latter.

cheers
DSD sends

FWIW, in my climate, I do ALL my root pruning and repotting in October and November. Our climate is not nearly as harsh as others, and I wouldn't recommend in colder zones. That being said, all of my trees are sitting on benches all winter and will often freeze solid while I am elsewhere, basking in the sunshine. Even after an especially cold and long winter, they all came through without issue this spring. Go figure.

Two things:

I was listening to Dennis V present at PSBA a couple of months ago. He echoed the thought that just because a tree “makes it through the winter on a bench” doesn’t mean it hasn’t been affected negatively.

Basking in the sunshine in Seattle winter?

Cheers
DSD sends

BobbyLane said:

Definitely not new or a special 'technique'
gardeners/landscapers have been transplanting trees during the bareroot period for decades. I took this and applied it to trees in pots with not much issues. I do the spring stuff too. however, our springs are so unpredictable now, you can never know what to expect afterwards. A lot of folk tend to disregard constantly changing weather conditions, when dishing out the same advice.

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Not disregarding changing weather conditions at all. Far from it. Those changes are easier to deal with in the spring than they are in the fall.

For instance, we've been getting substantially "front loaded" winters in the last few years, with early plunges in temps to the low 20s (-6 to - 3 or so) for prolonged periods by Thanksgiving. I have to protect things much sooner than usual. There is nothing I can really do beyond mulching trees into garden beds. That kind of deep cold affects roots in the mulch if it sticks around for more than a couple of nights. Cut roots, or new roots, that freeze are dead roots. That cold continues for months. Those cold snaps are the BEGINNING not the end, of winter.

In the Spring, we also get late freezes and frosts--from some FB post records, I have seen frost as late as the third week in May. Farther north, frost can continue into June. While those late cold snaps are dangerous, I simply bring trees inside until they pass and they do pass within days or weeks, not months.

The U.K. is warmed by the Gulf Stream. Many of us don't have that luxury. We have continental climates, not maritime--moist and relatively warm. We have extremes in heat, cold, precipitation (too much, not enough) and storms (hurricanes, tornados, etc). Those of us in continental climates deal with constant changes.

Paradox said:

What species are we talking about?

Sounds like BS to me.
In order for roots to keep growing, the tree can't be allowed to go dormant.

For species that need dormancy, not allowing dormancy is a bad idea that could and probably will weaken the tree which is not beneficial. Weak trees dont grow well.

Do that too many years in a row and the tree will die.

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100% agree

James89 said:

Late summer repotting

Spruce # 87 It's called 'late summer repotting' Never ever fall! Summer is until mid-September. But that's already LATE. I have repotted a huge spruce yesterday with Thomas. Now starts the repotting time until first week of September. You have to watch two things. General health of tree. Do not...

www.bonsainut.com

This seems a better link for summer repotting. Let me know if there are any links for autumn/ early winter potting

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What you should ask yourself is- how many bonsai has Geoff repotted in early winter with great success? in the UK i assume....sounds risky to me, unless it was done in extremely controlled conditions.

rockm said:

Do the math--sever roots in spring--6 months of regeneration/nutrient storage time. Maximizes root activity in the fall--Sever roots in the late summer you will get possibly three months of growth before dormancy if you're lucky... That timing also removes resources accumulated during the spring summer. Root growth slows and/or ceases when soil temps drop below 35 or so. With fall root pruning you're betting on a mild winter--which might be the case in the U.K.--most of the time, but in most of North America, we get substantially low wintertime temperatures.

The fall repotting stuff comes up all the time, but it's simply a mostly lesser alternative to springtime repotting. It's not some new discovery.

Click to expand...

I agree with all of the above. I would only try to nail a fall repot if I REALLY want to have a tree established before spring kicks off. But it does seem like 'threading the needle' for those in cold climates and best reserved for experts who really know their seasons and the health of the tree being repotted.
Also, big difference between up potting, slip potting, and root pruning with downpotting.

An autumn downpotting sounds like a tree killing move for most climates, but a slip pot or up pot should be alright if you have enough growing time in your area to recover before winter.