Cutting Taproot of Pre-bonsai when Thickening Trunk

[Delius]

Morning everyone,

I have a JM and Japanese Cherry pre-bonsai, and I’m repotting them early spring. I’m wondering whether I should cut off the taproot when doing so. I’ve purchased them this year and haven’t checked the roots yet.

The JM has had a trunk chop and is now growing it’s second part of the trunk. Bottom part of the trunk is about 2 inches.

The Cherry has a double trunk and hasn’t been chopped yet, I think I’ll do that the year after next. The bottom part of the trunk is a little over 2 inches.

Should I cut off the taproot? If so, by how much?

Thanks in advance for any help!

 

[Wires_Guy_wires]

Not all plants produce a tap root in every condition.
Since you haven't checked the roots, you might not have to cut one.

I'm a fan of doing the harshest work first, so cutting a tap root off is one of the first things I would do. The rest of the development can wait. Those other roots can help fuel growth, and so does that tap root.. But that tap root will get more and more difficult to remove; the larger it gets, the larger the cut and the slower the recovery.
If the cut kills my plant, I'd rather see it happen sooner than later.

 

[Shibui]

My experience is that very few trees grow tap roots like we imagine. Most quickly send out lateral roots searching for the best nutrients and water which is often closer to the surface. Your trees will probably also have some roots going deeper but most likely quite a few rather than a single tap root. It's those vertical roots you need to remove. Like @Wires_Guy_wires says, doing your major root work early is good because younger plants recover much faster than older ones. In addition, the sooner you can make your trees rely on the laterals the quicker the trunk will thicken and flare out near the base. Good nebari is based on early root intervention.
Both cherry and Japanese maple can cope with quite harsh root reduction. Even with trees that size I would cut all vertical roots as short as possible. Remove them completely if possible. At the same time I also reduce laterals just leaving around 1 trunk thickness long roots. This reduction forces those roots to branch out which will also give you much better nebari in the longer term.

 

[leatherback]

There is an answer, which has been seconded, let me Third is. Agreed, rootwork needs to be done early in the process, and needs to be repeated every 2-3 years to ensure you stop individual roots dominating the rootball.

 

[Cajunrider]

For me, cutting the tap root happens on the first date with practically all my trees.

 

[defra]

and if you still are unsure.... start with the roots because after that you cant touch them for 2-3 years and work on whats above the ground.
but also i doubt if there will be any straight down growing tap root since you say they are bought as pre bonsai wich in my experience are trees prepared to be a bonsai so at least they have been root pruned once and potted up.
good luck

 

[Delius]

Not all plants produce a tap root in every condition.
Since you haven't checked the roots, you might not have to cut one.

I'm a fan of doing the harshest work first, so cutting a tap root off is one of the first things I would do. The rest of the development can wait. Those other roots can help fuel growth, and so does that tap root.. But that tap root will get more and more difficult to remove; the larger it gets, the larger the cut and the slower the recovery.
If the cut kills my plant, I'd rather see it happen sooner than later.

Cheers, that fits with what feels right to me so that’s great.

 

[Delius]

Thanks for the advice, it’s much appreciated!

It’s what I prefer to do too, so that’s an added benefit.

 

[Ja_De]

Framing and standing the walls before your foundation footings are poured... Uh, no.
I've had great results in "ground potting" trees in some abundantly sandy soil. The great specimen maple bonsai are those with nebari like talons grasping the soil in the most shallow pot possible; so root prune with this in mind BUT YOU CAN PRUNE THE ROOTS MORE THAN ONCE. Set in the ground pot or box, the sandy soil should promote fibrous root growth. Feed these when you see new growth up top.

The cynic in me realizes " pre- bonsai" describes nearly all trees no matter the condition and I'm sure you've seen how all that's needed to qualify a tree as bonsai is a Chinese man fishing. So...

 

[Delius]

Framing and standing the walls before your foundation footings are poured... Uh, no.
I've had great results in "ground potting" trees in some abundantly sandy soil. The great specimen maple bonsai are those with nebari like talons grasping the soil in the most shallow pot possible; so root prune with this in mind BUT YOU CAN PRUNE THE ROOTS MORE THAN ONCE. Set in the ground pot or box, the sandy soil should promote fibrous root growth. Feed these when you see new growth up top.

The cynic in me realizes " pre- bonsai" describes nearly all trees no matter the condition and I'm sure you've seen how all that's needed to qualify a tree as bonsai is a Chinese man fishing. So...

Makes sense, what I was thinking is that maybe when you’re still mainly growing the trunk and not yet focusing on the branches, it might make sense to not disturb the roots too much so it can grow freely.

Sand I haven’t seen mentioned that often, I’ll give it a try, thanks.

 

[defra]

Makes sense, what I was thinking is that maybe when you’re still mainly growing the trunk and not yet focusing on the branches, it might make sense to not disturb the roots too much so it can grow freely.

Sand I haven’t seen mentioned that often, I’ll give it a try, thanks.

yes but the wound you create by cutting of big roots heal faster in the ground also versus in a pot.
also roots thicken faster in the ground because they can extend unlimited.
so for growing the trunk primary branching and the start of the future nebari go with the ground and then refine in a pot afterwards.
it doesnt mean it can be done other ways but thats been proven to be the fastest way.

 

[leatherback]

what I was thinking is that maybe when you’re still mainly growing the trunk and not yet focusing on the branches, it might make sense to not disturb the roots too much so it can grow freely.

but that would give you a lmited number of ugly fat roots.

 

[Ja_De]

Makes sense, what I was thinking is that maybe when you’re still mainly growing the trunk and not yet focusing on the branches, it might make sense to not disturb the roots too much so it can grow freely.

Sand I haven’t seen mentioned that often, I’ll give it a try, thanks.

There's a balance to be struck for sure. I'm certainly one who's guilty of too much meddling. I agree with you, there's such a a thing as too much.

I believe Peter Chan informed me of sandy soil encouraging fine roots to grow, in one of his books.

 

[RaginCajun]

Japanese black pine are grown from seed and at just a few weeks of age the seedlings are pulled, the roots cut off smooth with a razor blade and then replanted as seedling cuttings. Many benefits to this method. Terry Erasmus has some good videos on the topic.
You just let the tree run wild afterwards to grow and thicken as usual. You get a much better start to nebari and you have a node at like ground level which you wouldn’t get otherwise.