AusBonsai

Its that time of year again. Members are talking about and asking about repotting and root pruning.
In case anyone is interested here are some photos of how I root prune first year seedlings to try to start a good radial nebari.
These are self seeded plants I have just dug from our garden beds. I'm hoping this will give others the confidence to really root prune their young trees.

Great post Shibui!

When you are repotting young or even older deciduous trees what is your preferred method of removing soil and untangling roots? using water or a rake?

Cheers
Matt

Hi Neil,
I have certainly been root pruning my trident maples this hard, and doing so already, despite there being a couple months of winter left.
Are there any deciduous species that in your experience do not tolerate this treatment?
Cheers,
Luke

Wow, there's not much left! I was starting to worry I'd taken too much off after cutting about 1/2 off

Can the same be done to Elms now?

WoW thanks for posting this. This is valuable knowledge to have especially at this time of year.
I have the same question as above. How many deciduous trees can tolerate such drastic pruning?
I recently replanted some JM and had to cut of a lot of vertical roots. What is left is similar to the pics above. I'm worried that they might not make it.

Thanks for posting this Shibui.

My questions are:

* Do the tree's lose vigour and grow slower as a result of this hard chop?
* Can one be as aggressive with more mature tree's - say 5 and 10 years?
* Do you find that the "stumps" left from the bigger cuts divide/promote roots from the open ends?

Thanks for going to the effort - perhaps a couple of photo's with some more mature tree's would help this fantastic thread!

Cheers!

hi Neil
i hope you don't mind but i'll try to share my thoughts about some of the questions asked.
here is a link to my website about root pruning:

http://bonsaisensation.com.au/how-to-prune/


regards

Tien

Hi Neil

Great post and I've been following your advice closely regarding root pruning and have much success, especially with JBP seedlings.
In terms of root pruning, the most severe I have knowledge of is the flat bottoming method and I know you have great success with tridents.

Is this month a good time to attempt flat bottoming on tridents?

Thanks,

When you are repotting young or even older deciduous trees what is your preferred method of removing soil and untangling roots? using water or a rake?

I usually use the root shears first. Just cut a few cm off all the way around and slice the tangled roots off the bottom. The most tangled spot is around the edge and bottom of the root ball. Once that is gone the remaining roots are much more radial and s single pointed root hook works pretty well. I'll try to get some photos when I repot next.

Are there any deciduous species that in your experience do not tolerate this treatment?

I generally cut tridents harder than others but the difference is pretty small. I have root pruned Japanese maples just as hard and most survive. I seem to get occasional deaths with Japanese maples and Chinese elms which I think is due to fungal infection. Seems to be worse when they sit in cold, wet mix and usually only affects odd trees, not general

Can the same be done to Elms now?

See above. I would wait till late winter. Last year after root pruning the Chinese elms from the grow beds I dusted the roots with fungicide and only had 1 die. Maybe that is an answer??? Always interested to hear of other theories.

I recently replanted some JM and had to cut of a lot of vertical roots. What is left is similar to the pics above. I'm worried that they might not make it

Normally they will be ok. I think keeping them slightly on the dry side is better - definitely not under the benches where they stay cold and wet. Always cut vertical roots as hard as you can - early. The younger and less developed trees will recover better than older trees with lots of branches.

* Do the tree's lose vigour and grow slower as a result of this hard chop?

No! They usually grow even quicker the following year because of all the new roots produced.

* Can one be as aggressive with more mature tree's - say 5 and 10 years?

I would not regard 5-10 years old as mature. The trees that are dug from the grow beds are 3-7 years old, sometimes older and are treated this way. I have sawed off roots up to 4 cm thick leaving those roots only 3-4 cm long. One of the points of this thread is to encourage people to make these root cuts early when you are also doing the most radical top reduction rather than leaving it until the tree is fully formed. then it will need to recover roots while supporting a full canopy above.

* Do you find that the "stumps" left from the bigger cuts divide/promote roots from the open ends?

YES I will find some photos but it is very obvious the following year when you can see lots of new roots coming out from the cambium around the cut end. The earlier you make these cuts the better divided the nebari will be.
I'll also add some photos of pruning established trees for you.

Is this month a good time to attempt flat bottoming on tridents?

I have not actually 'flat bottomed' tridents as we do with olives. They may well survive that but I have not done it. I do cut all vertical roots back as hard as possible - ie remove them completely - but I always leave some stubs of the lateral roots for new roots to grow from.

Here's a pictorial of the next stage of root pruning - assuming the tree has already had preliminary root pruning to establish reasonable radial roots. If you buy nursery stock or starters you will probably start about here but may have to start at step 1 above if there are few thick roots. notes:
The radial root system on this tree is the result of hard initial root pruning (as above) last year.
I would root prune like this even if the tree was to be grown on in a larger pot or in the ground. This sort of pruning sets the root system up to develop really great nebari. Pruning the roots will not inhibit growth. Trees treated like this will grow just as fast in subsequent years.

Hi shubui : Neil to how old a tree would you stop doing that much
Pruning to I have a couple of trees between 10 to15years old in large containers 250mm+

Thanks for posting neil.... never though they would survive cutting that many roots.

Thanks for posting this, it's good to see how far you can take them back.

Thanks Neil just got my first trident in. Helps a lot for next year. I received it bare rooted so I didn't do the big chop after it being posted.

Sent from my GT-S5300 using Tapatalk 2