Autumn repotting of Deciduous trees.

[Grant Bowie]

When I lived in Sydney around 1989 I started repotting my deciduous trees in late autumn while they were still in leaf. This came from a stray comment by Ray Nesci that because of the number of trees he had to dig out of the ground he started as soon as the leaves fell (or earlier). This is a major dig up and prune of the roots so I thought a gentler repot of an established, deciduous bonsai would be no problem.

The first tree was a Japanese maple. Japanese maples can be a bit iffy in Sydney so it was with a small degree of trepidation that I did the repot, cut the roots and left the leaves on. The earth did not shake; no thunderbolts from angry gods, the tree just proceeded orderly to winter and was fine the next year.

I continued the process when I moved to the Southern Highlands also with no problems. It was cooler in winter so I moved the repotting forward 2 to 4 weeks.

When I moved to Canberra I did not dare to repot in Autumn; and no one else did it either. Winter is long and cold in Canberra so if you prune the roots just prior to winter you then have the tree sit with cut roots in damp, cold soil for up to 5 or 6 months. I checked again recently and again the answer was that no they did not repot in Autumn because they were rightly afraid to do it.

While repotting my conifers over the last 2 weeks I spied a Trident that was sitting in a broken pot. I had accidentally broken the pot during some shelving construction in November or December. That time of year can be very hot; the tree was full of new soft growth and growing like crazy. I did not have a pot of the same depth but a bit bigger to slip it into, so I just taped up the pot, trimmed the excess growth and a little bit of damages, and put it back on the shelf.

So on 17th March, St Patricks day, (7 days ago) I pulled a beautiful Japanese pot off the shelf and prepared it for the trident maple. The pot was deeper but smaller so I ended up having to trim off a lot of roots to fit it into the pot. The result is shown below. I did not trim off any growth or defoliate the tree.

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As you can see the pot is sort of stitched together with wire so the broken pot had not fallen off the tree when broken.

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I misted the tree frequently for the first 4 days and was then away for 24 hours and then misted a few times occasionally on return.

[Grant Bowie]

So what are the likely outcomes, advantages and disadvantages of repotting in Autumn?

Outcome.

The tree will settle quickly into its rhythm and prepare for winter.
It will initiate lots of root growth.
It will not defoliate itself due to the repot.
It will most likely not put out new foliage.
It will most likely lose its leaves later than normal and not colour up early either.

Advantages.

You can lengthen your repotting times for deciduous trees.
You can change pots if necessary for artistic reasons or due to mishap.
The weather is warm and consistent and the roots grow quickly without foliage growth.
You can control the environment by shading and misting; or put inside for a day if dreadfully hot and windy.
No long period of tree with cut roots in cold soil for many months

Disadvantages.

You could have a spell of really hot, windy weather and you are away from home or at work.
You may trigger foliage growth depending on the species of tree.

I left the tree bushy so that it forces as much root growth as possible; and if it broke into new growth I can trim it back in 3 months time to my taste.

I repotted a Corky Bark Elm 4 days ago and a Chinese elm today.

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Grant

[Grant Bowie]

Temperatures during which the Trident maple was repotted were,

26 degrees on Tuesday when repotted.
30
32
30
22
24
28 and windy at the moment, expecting 29 or 30 today.

Grant

[legoman_iac]

Hi Grant,

Thanks for sharing. Definitely something to think about. So are you still in Canberra? Or back in Sydney?

I'm in Sydney, and am attempting my first trident air layer. Was about to try separating him however have had a bridged callus so holding off a few more weeks (discussion in another thread not trying to hijack this one). Am very curious if you think "autumn repotting" applies to "air layer separation" too?

- Daniel

[Grant Bowie]

Hi Grant,

Thanks for sharing. Definitely something to think about. So are you still in Canberra? Or back in Sydney?

I'm in Sydney, and am attempting my first trident air layer. Was about to try separating him however have had a bridged callus so holding off a few more weeks (discussion in another thread not trying to hijack this one). Am very curious if you think "autumn repotting" applies to "air layer separation" too?

- Daniel

I still live in Canberra.

In this instance; what you can do may depend on where you live in Sydney; i.e. Neutral Bay vs Riverstone.

You can do just about anything in a mild, steady climate like Neutral Bay but less and less where it is extremely hot and extremely cold. I used to live in Bankstown, Ermington, Eastwood, Yagoona etc so it is a bit between the two extremes.

I did spend 2 years in Coogee on top of a cliff right near the sea and did not even own a heater; it was so mild.

So, re separation of an air layer, you may still have plenty of time.

Grant

[dansai]

You're timing is great Grant. I was just looking up about times to repot maples. I have finally got round to potting up my last seedling maples. A lot of the ones I did about 4 weeks ago lost their leaves on a hot windy day and are back budding now. All were root pruned pretty hard. I was concerned about the timing but thought I would be faced with bigger root problems if I didn't do it. Also thought seedlings would be more adaptable with timing.

The reason I was looking up about timing was I wondering about doing another repot next autumn after they have put on a seasons of growth rather than wait until the following spring so I can really sort the roots out properly. I have a very mild winter with only the occasional light frost and rarely near the nursery.

[Grant Bowie]

You're timing is great Grant. I was just looking up about times to repot maples. I have finally got round to potting up my last seedling maples. A lot of the ones I did about 4 weeks ago lost their leaves on a hot windy day and are back budding now. All were root pruned pretty hard. I was concerned about the timing but thought I would be faced with bigger root problems if I didn't do it. Also thought seedlings would be more adaptable with timing.

The reason I was looking up about timing was I wondering about doing another repot next autumn after they have put on a seasons of growth rather than wait until the following spring so I can really sort the roots out properly. I have a very mild winter with only the occasional light frost and rarely near the nursery.

Sounds like you could leave it a month or more later than what you did. Right up till early May or so.

Grant

[legoman_iac]

In this instance; what you can do may depend on where you live in Sydney; i.e. Neutral Bay vs Riverstone ... So, re separation of an air layer, you may still have plenty of time.

Grant

Hey Grant,

I'm in the milder part of Sydney in Bondi Junction, will leave it much later than. Good to know all this, I'd just be waiting for early spring otherwise.

Thanks again!

- Daniel

[xIIRevoEvoS]

In this instance; what you can do may depend on where you live in Sydney; i.e. Neutral Bay vs Riverstone ... So, re separation of an air layer, you may still have plenty of time.

Grant

Hey Grant,

I'm in the milder part of Sydney in Bondi Junction, will leave it much later than. Good to know all this, I'd just be waiting for early spring otherwise.

Thanks again!

- Daniel

I think personally with the weather condition, its better to wait till June to repot. Sydney weather has changed abit from rainy to sunny to very hot. Quite unusual for Autumn this year

[dansai]

Some interesting reading.

http://www.botanicalgarden.ubc.ca/forum ... hp?t=33024

http://www.evergreengardenworks.com/fallpot.html

So Japanese maples may have problems when soil temps get to freezing if repotted and root pruned in Autumn. As my winter here is generally warm with daytime temps over 10C and only night times occasionally going to below about 5C I should be right for Autumn repotting. Interestingly on a few other sites (general garden sites talking about Japanese Maples in containers, not Bonsai) there was many comments about the retardation of growth after early spring root pruning. The autumn root growth, if it can be protected from freezing, gives the plant a head start for the spring growth flush.

[Raymond]

Thanks for the read, interesting topic. My main curiosity is the wire... I've never seen a tree re-potted like that.

[Grant Bowie]

Thanks for the read, interesting topic. My main curiosity is the wire... I've never seen a tree re-potted like that.

The wires when done this way form a very secure cage over the roots and can be made to come closer to the centre by twisting the wires together a number of turns till about the height of the top of the root system.

If a simple repot with a good established root system where you want the wire closer to the edge of the pot, you don't twist it together as high.

It is a good system and the tree will be extremely stable.

Grant

[Raymond]

Thanks for the read, interesting topic. My main curiosity is the wire... I've never seen a tree re-potted like that.

The wires when done this way form a very secure cage over the roots and can be made to come closer to the centre by twisting the wires together a number of turns till about the height of the top of the root system.

If a simple repot with a good established root system where you want the wire closer to the edge of the pot, you don't twist it together as high.

It is a good system and the tree will be extremely stable.

Grant

Thanks

[Scott Roxburgh]

How much root work did you do? Raking? or do you only recommend for established root pads?

[JaseH]

Reihou pots looking good Grant!