Growing a thick root mass

[Lazylightningny]

The ideal bonsai root mass is comprised of a thick mat of small feeder roots, flat on the bottom. Let's say you bare root a typical nursery plant. There will be a lot of thick anchor roots that terminate in feeder roots. How do you get from there to the beautiful, dense mat of feeder roots with no thick anchor roots needed for bonsai culture? Especially for conifers, it's a daunting concept.

 

[Saddler]

The way I have had consistent success with my maples and growing fine roots is root pruning and repotting every spring. Changing my growing medium also helped, but the repotting every year has left me with the nicest roots, which I find is a double edged sword because it slows down the trees growth for me, but I get shorter internodes on my first flush. Am I repotting too early? To late?, not sure yet. I starting to come up with repotting that goes something like 2 year, 1 year, 2 year, 1 year and adjust as I need. My idea is to try and but back after the two years to get shorter internodes. Also in my experience this will all go out the window when I figure some small detail out that disrupts the whole thing. Haha. I hope someone chimes in with some details about how they do that does that disruption sooner rather then later.

 

[Wires_Guy_wires]

Roots can change their structure over time. Fat ropey roots can actually slim down, make adventitious roots and become feeders. Sometimes they need to be replaced by the plant. Not all plants are equally capable of converting.
There are multiple ways to encourage this, one of which is air. Dry air kills root tips and - in the same process as clipping growing green tips to produce side shoots - the roots wil branch. Repeat this process often, and you'll get a mat of feeders. Smartpots and other "breathing" nursery pots lean on this principle.
Collanders, andersons flats, all of those containers have the same thing going on: a bunch of air and some water.
Coarse soil will help with this a lot. In my JRP seedlings it takes roughly a year for a taproot to change in a mat of feeders. In regular soil, this only happens when there's serious watering issues.

Physical root pruning can help, but it means you're damaging a plant. I'm not sure if that would be faster or more efficient, because instead of natural processes taking place, you're breaking down structures that need repair. If a root dies due to air exposure, usually there's no repair necessary; the air killed it off and every nutrient and bit of water has been sucked out of it. The plant just rejects it in a process called abscission. Abscission always takes less energy than repair.

 

[Anthony]

Try this -

less than 3 inches deep and soil is 5 mm

Roots have no choice but to grow out and when circling are
on the end.
Can be cut, and leveled underneath to handle tap root
formation.

If you wish you can also design with a drill or hot nail etc....
like an air-pot.
Good Day
Anthony

UV plastic pot saucer, can be had down here to 2 feet.
You can also glue on feet / lifts.

 

[0soyoung]

Physical root pruning can help, but it means you're damaging a plant. I'm not sure if that would be faster or more efficient, because instead of natural processes taking place, you're breaking down structures that need repair. If a root dies due to air exposure, usually there's no repair necessary; the air killed it off and every nutrient and bit of water has been sucked out of it. The plant just rejects it in a process called abscission. Abscission always takes less energy than repair.

I certainly agree with regard to foliage and abscission, but roots are a sink tissue. Maybe amylase manages to convert starches to sugars that can be moved, but I think it is minimal --> IOW carbohydrates are lost in either case. Clip the tip or desiccate it and ethylene causes branching. Meanwhile, at a cut surface, auxin piles up and new roots are initiated directly. I don't think this part happens quite so quickly with air pruning (not that it really matters).

 

[Lazylightningny]

Fifteen or so newly bare rooted plants, in pond baskets with bonsai soil, most of them in sunlight. My plan was to let them air prune for the rest of the year, and lightly root prune deciduous species in the spring. I was planning to let conifers grow for an additional year before root pruning. Plants that I felt were not healthy enough after bare rooting were planted back into the ground to recover.

 

[Clicio]

rooting were planted back into the ground to recover.

In which soil?

 

[Wires_Guy_wires]

I certainly agree with regard to foliage and abscission, but roots are a sink tissue. Maybe amylase manages to convert starches to sugars that can be moved, but I think it is minimal --> IOW carbohydrates are lost in either case. Clip the tip or desiccate it and ethylene causes branching. Meanwhile, at a cut surface, auxin piles up and new roots are initiated directly. I don't think this part happens quite so quickly with air pruning (not that it really matters).

Indeed it does not happen so quickly, and that's where the advantages lie. The plant has more time to naturally regenerate (and 'decide' which way to go is best) in dessication style pruning. With mechanical pruning, the plant is forced, no decision making, only responsive action. Roots might grow on places where they would certainly die later because they are forced to grow.
Air pruning is not as stressful for a plant as mechanical pruning, it does not make wounds and it doesn't influence the system as a whole with shocks of auxin depletion (sink towards the roots for restauration). It's not just carbohydrates in the roots that are lost, it's also the general redirection of nutrient streams towards the roots, streams that aren't being used higher up. Air pruned plants tend to have a steady slow release dosage; you don't see growth slow down when it's building feeders. Whereas with mechanical pruning, you do.
If a stable growth pattern is your aim, I'd go with air pruning.

But whatever your preferred technique is, pruning helps. For the best feeder roots, go with aeroponics. What I've seen there, damn. No other techniques even come close to what that yields in root mat mass and volume.

Excuse me now, I'll be going outside for a happy dance. Today we had the first actual rain in 2 whole months! For a country that's basically a drained swamp, that's an unusually dry summer.

 

[KiwiPlantGuy]

Hi @Lazylightningny
This thread has got quite complicated, doesn’t have much relevance, so I thought I would add my newbie bonsai/experienced Horticulture view points.
Nursery grown plants seem to always have a lot of feeder roots, but to help your thinking-

Deciduous trees can be root chopped via anchor roots real hard (if you have some feeder roots to help recovery). Also you can cut any heavy downward growing roots to start the flat plane of roots. It might take a few years to get feeder roots and not many big horizontal roots.

Evergreen/Conifer trees seem to be a little more picky/fussy. So I have seen the use of colanders/ wooden boxes with much success. If you have seedlings or small potted conifers then the above would work nicely.
Obviously if you have a large tree in a large pot, it might take 2-5 years to reduce nursery pot size in successive root cutbacks. IE- cut too much root in one go = seems to always lead to slow recovery or death.
This is my method, and am happy to read others opinions to adjust my methods.
Charles

 

[leatherback]

Indeed it does not happen so quickly, and that's where the advantages lie. The plant has more time to naturally regenerate (and 'decide' which way to go is best) in dessication style pruning.

There isw, of course, also a disadvantage.
The OP was talking about how to go from existing anchor roots to fine roots desireably in bonsai. You will need to eventually stimulate the tree to let go of the main roots, and start building more smalle roots on the main trunk, unless you are lucky and get a nursery tree with a decent nebari. To me it feel that just air pruning will not do this. However, mechanical pruning of the main roots, say, back to the first side-roots, will stimulare creation of new primary roots. Right?

 

[BobbyLane]

The ideal bonsai root mass is comprised of a thick mat of small feeder roots, flat on the bottom. Let's say you bare root a typical nursery plant. There will be a lot of thick anchor roots that terminate in feeder roots. How do you get from there to the beautiful, dense mat of feeder roots with no thick anchor roots needed for bonsai culture? Especially for conifers, it's a daunting concept.

its a progressive thing from my experience, in re to deciduous its not always completely necessary to bare root a nursery tree and put it straight into a nursery pot, it would take far longer to recover in my experience. so the root ball is reduced in stages.... i think what youre asking is how does a nursery root ball go from this,
20180320_124031 by Bobby Lane, on Flickr

to this
20180321_175048 by Bobby Lane, on Flickr

with a bit of elbow grease

20170929_183246 by Bobby Lane, on Flickr
2017-10-15_03-19-34 by Bobby Lane, on Flickr

the yew went back into a pot of similar size and depth and will be reduced gradually

there is no need to remove all the thick heavy roots in one go, some can be cut out, others can be reduced

 

[Lazylightningny]

There isw, of course, also a disadvantage.
The OP was talking about how to go from existing anchor roots to fine roots desireably in bonsai. You will need to eventually stimulate the tree to let go of the main roots, and start building more smalle roots on the main trunk, unless you are lucky and get a nursery tree with a decent nebari. To me it feel that just air pruning will not do this. However, mechanical pruning of the main roots, say, back to the first side-roots, will stimulare creation of new primary roots. Right?

That seems to be the most sensible route- a combination of cycles of a year of air pruning concluded by root pruning until sufficient mass is obtained.

For those who collect yamadori, what's your method? Should be a similar situation.

 

[Wires_Guy_wires]

There isw, of course, also a disadvantage.
The OP was talking about how to go from existing anchor roots to fine roots desireably in bonsai. You will need to eventually stimulate the tree to let go of the main roots, and start building more smalle roots on the main trunk, unless you are lucky and get a nursery tree with a decent nebari. To me it feel that just air pruning will not do this. However, mechanical pruning of the main roots, say, back to the first side-roots, will stimulare creation of new primary roots. Right?

Based on feelings, you get faster result with mechanical pruning. However, in a way it's like pulling teeth out of a toddler; sure, adult teeth will show up eventually. And maybe a bit faster. But you'll have trouble feeding the kid until the pain has stopped and it has grown some teeth again, and the teeth will grow in random directions. They might have to be pulled or corrected later.
When building root systems, we can't force directions. But we can keep the tree from going through the pain, and keep it from not being able to eat for a few weeks.

Root death from air exposure is slow. The root senses this and signals further back to branch out. It's like leaving the teeth in a toddler until they fall out. The living body decides what course of action is best for it's steady development: not too much, not too little. The tree can keep eating and drinking, the foliage can keep developing.

Keep in mind I'm not daying there's a wrong or right way. I'm just explaining my personal motives for having a preference: steady and dependable growth rate.

 

[milehigh_7]

Strainer and fast draining mix with about 50% DE from zero lateral roots (I cut them all off) to this in one growing season.

 

[Saddler]

When building root systems, we can't force directions. But we can keep the tree from going through the pain, and keep it from not being able to eat for a few weeks.

It's like leaving the teeth in a toddler until they fall out. The living body decides what course of action is best for it's steady development: not too much, not too little.

To use your teeth analogy, dentists will often pull teeth out early because they pushing aside the neighboring teeth. This goes for roots. Mechanical pruning does the same. Cut back the stronger roots to let the weaker roots grow.

As for building root systems and forcing directions, yes we can. I am doing it more and more often. I use pins with my tree on a board to not only get them to grow directly away from the trunk but try and give them a little movement side to side. Next spring I will try adding some up and down too when I repot.

I’m not saying airpruning cant be a great method, I’ll probably be trying it again next year after having it kill a bunch of trees a few years ago. It’s just one trick in a bag of many to get where you need to go. As I said earlier, I have found repotting/root pruning gives the best results for me so far.

 

[ysrgrathe]

Big roots will never get smaller. At some point you need to cut them. Read the Ebihara thread that Markyscott posted, it has everything there is to know for maples.
https://www.bonsainut.com/threads/ebihara-maples.18215/

 

[milehigh_7]

It's also going to depend on species. If it's a Vitex your method is as follows:

 

[Anthony]

Air-pot and normal container.
Same amount of soil.
The air-pot evolved more branches and smalerl leaves.
Here they are in the normal container and bonsai pot [ air-pot specimen ]
Good Day
Anthony

Both are the same age.

 

[Anthony]

Here they are side by side .
The tape marks the soil level in the air-pot

Also air-pot by earthenware pot

 

[It's Kev]

@Anthony what is an air-pot?