Why leave nebari buried??

[Jzack605]

So I’ve seen a few people refer to leaving the nebari buried during development. This is confusing to me as I spend a fair amount of time with an air spade and by hand uncovering root collars on trees, root invigoration and pruning out girdling and adventitious roots because people often bury trees too deep to their detriment.

why would it be beneficial for bonsai?

 

[Paulpash]

So I’ve seen a few people refer to leaving the nebari buried during development. This is confusing to me as I spend a fair amount of time with an air spade and by hand uncovering root collars on trees, root invigoration and pruning out girdling and adventitious roots because people often bury trees too deep to their detriment.

why would it be beneficial for bonsai?

Exposing the nebari to air has several disadvantages, namely
1. Further ramification and side roots will not form as fragile roots will die in the drying out process.
2. Once roots are exposed to the air long term their nature starts to change, bark starts to form and this further prevents adventitious growth.
3. Roots prefer darkness. Light further discourages root growth.

 

[MrWunderful]

In addition to what is said above, it helps the upper most roots develop to provide a better basal flare.

 

[Zach Smith]

So I’ve seen a few people refer to leaving the nebari buried during development. This is confusing to me as I spend a fair amount of time with an air spade and by hand uncovering root collars on trees, root invigoration and pruning out girdling and adventitious roots because people often bury trees too deep to their detriment.

why would it be beneficial for bonsai?

On newly collected trees it's vital to bury the surface roots sufficiently to prevent drying out of both the chopped ends of the larger surface roots, as well as to prevent drying out of new roots that sprout from those chopped ends. Most new enthusiasts want to show off the surface roots of their newly collected trees right from the start. Bad idea. They can be revealed again in two or three years when the tree is ready to go to a bonsai pot.

 

[hemmy]

pruning out girdling and adventitious roots because people often bury trees too deep to their detriment.

why would it be beneficial for bonsai?

In addition to the the above responses, it should also be pointed out that you have to arrange and work the roots on your container trees to prevent girdling and poor arrangement.

 

[Wires_Guy_wires]

3. Roots prefer darkness. Light further discourages root growth.

I have seen roughly 1.500.000 cases to prove otherwise. That's one point five million. Those are just the ones I've seen with my own eyes, not the ones I've read about, which should be roughly ten times that number.
The same myth exists about fungi, which just like roots, can thrive in light.
If light would discourage root growth, I would expect at least half of all rooting media in scientific literature to be non-transparent. Yet, in 99% of the cases it's either transparent agar or some other transparent gelling agent. I have plowed through 6 books and thousands of pages of literature about roots, only a few of them mention using darkness to their advantage and that's mostly due to the scientists using a paper that has been disproved many times. That paper states that IBA breaks down within four hours when exposed to light. My own experiments have proven that media+IBA exposed to light for six months, still has better rooting than media without IBA exposed to light for the same amount of time. I was pretty perplexed to see those results. I repeated the experiment on a large scale (N=1200) and found the same results; yes IBA does degrade, but not at the level the literature states as factual.

The myth about roots and darkness persists because of multiple reasons; when light enters the soil, algae can grow. Those can secrete toxins that kill/change the biome of the soil. Algae tend to cake up and clog the air pockets in a soil as well by forming dense mats.
Roots require a cooler environment compared to the rest of the tree, when light enters, usually infrared can enter too. Now you can argue about infrared being light, but a LED not emitting infrared does not hurt the roots. Some roots can make chlorophyll and photosynthesize on their own, this happens when they're exposed to light. Botanists, especially the ones going for aesthetics, have always deemed this as a bad quality while it's actually just a plant functioning as it should.
Where there's light, there's usually dry air too, and roots don't like dry air.. In that case it's a mix up of causality.
There are probably a lot more of those mix ups, these were just a few I can whip out from what I've seen on gardening forums. It's a very common misconception that roots don't like light, I'd like to help it out of the world.

 

[Paulpash]

While I bow most humbly to your lab experience of root development in light I was focusing on the real world application and associated implications on my benches. I just 'know' that adventitious surface roots covered initially with chopped sphagnum will, with high regularity, pop on species like Elm, Pyracantha, Maple and Blackthorn.

 

[sorce]

The light thing is an "it depends".
Enough water, and it doesn't matter.

We tend to associate light with humidity and temp, but in these cases, they are not related.

As to the question....
It's give and take....
We don't hide it for display.

As always....
Balance.

Reasons vs. Reasons.

Reason win

Sorce

 

[rockm]

I would say you're talking about two different things--exposure and sunlight. I don't think roots have a problem with light itself. I do think newly sprouted surface roots have an issue with exposure and drying out. Exposed roots are subject to the drying effects of wind and intense sun in the summer. I have also found that a covering of chopped sphagnum moss on the soil's surface after a root prune produces many more roots on the surface and an inch down because it traps a humid layer against the roots and soil, allowing a more even environment....

 

[Lars Grimm]

I would say you're talking about two different things--exposure and sunlight. I don't think roots have a problem with light itself. I do think newly sprouted surface roots have an issue with exposure and drying out. Exposed roots are subject to the drying effects of wind and intense sun in the summer. I have also found that a covering of chopped sphagnum moss on the soil's surface after a root prune produces many more roots on the surface and an inch down because it traps a humid layer against the roots and soil, allowing a more even environment....

Does this mean that clear vs dark plastic for air layering makes no difference? Presumably the humidity should be high in both, although the temperature would be greater with the clear plastic.

 

[0soyoung]

So I’ve seen a few people refer to leaving the nebari buried during development. This is confusing to me as I spend a fair amount of time with an air spade and by hand uncovering root collars on trees, root invigoration and pruning out girdling and adventitious roots because people often bury trees too deep to their detriment.

why would it be beneficial for bonsai?

I note to you that when we bonsai-ists say 'buried' we mean maybe an inch under a substrate with high air-filled-porosity.
You work on trees with roots that are buried under a foot or more of soil with very low AFP, I think - they are truly buried and suffocating.

 

[Shibui]

Does this mean that clear vs dark plastic for air layering makes no difference? Presumably the humidity should be high in both, although the temperature would be greater with the clear plastic.

That I my understanding. Clear plastic is fine for air layers as long as it does not get too hot and in most cases air layers are protected by the leaves around them.
As mentioned, it is not light or air, but moisture that affects roots. The misconception arises because air and light tend to promote drying which is the killer of roots.

I note to you that when we bonsai-ists say 'buried' we mean maybe an inch under a substrate with high air-filled-porosity.
You work on trees with roots that are buried under a foot or more of soil with very low AFP, I think - they are truly buried and suffocating.

Agree. I think this was the initial misconception. Light covering is good. Deep burial can be detrimental for bonsai though not usually harmful for the tree. Deep burial will often promote new roots just below the surface. By the time you realise the trunk has already expanded where the new roots are growing and the original nebari cannot be used (if it was any good). i discovered this years ago when I first started to field grow trees for bonsai. At one stage I used it to advantage by planting trees deep there was no need to do any root work on the original roots. In 2 years there would be a new set of surface roots, usually all round the trunk and better than the ones I was producing with root pruning and burying a bit shallower.

There has been a lot of work to show that deep planting can be beneficial. Roots deep down have more access to moisture to survive the summer and most species are able to grow new roots near the surface. The new surface roots eventually take over from the deeper ones, especially when the original roots are circling and tangled as is often the case with container grown plants.

 

[Potawatomi13]

1. Further ramification and side roots will not form as fragile roots will die in the drying out process.

.

This seems #1 important esssence for non root exposure in development. As to removing circling, strangling or other undesirable roots these can be simply dealt with during repotting.

 

[Vance Wood]

While I bow most humbly to your lab experience of root development in light I was focusing on the real world application and associated implications on my benches. I just 'know' that adventitious surface roots covered initially with chopped sphagnum will, with high regularity, pop on species like Elm, Pyracantha, Maple and Blackthorn.

The key is not whether you do it---it is how and with what you do it: Chopped sphagnum moss is the key.

 

[Paulpash]

The key is not whether you do it---it is how and with what you do it: Chopped sphagnum moss is the key.

Can I just add that over my pots covered with moss I put green mesh shading. I did this initially to stop the dang birds pecking off all the moss & substrate below but it also ensures that the moss stays moist and cool. I've subsequently found that this helps adventitious root growth even more and would use this method even if by some miracle the blackbirds declared a turf war truce.

 

[Wires_Guy_wires]

Does this mean that clear vs dark plastic for air layering makes no difference? Presumably the humidity should be high in both, although the temperature would be greater with the clear plastic.

I think dark plastic would be even worse than transparent because it heats up in the sunlight.

As for the mesh @Paulpash mentions, I can agree on that! Blackbirds are a serious pest in my yard as well, they scoop out entire pots within minutes and they aren't scared to pull seedlings - or even established shohin - out of their pots.

I also agree on the real world implications, lab studies aren't worth jack if they can't be applied. I think we've come full circle with a real world application: air layering. If light has a limited effect on phytohormones, and little to no effect on root formation, a transparent container could be beneficial for multiple reasons. Not only because the sphagnum stays alive and fends off fungi, but also because we can see how far along an air layer is, if it needs more water or not, and because transparent containers don't capture/trap as much heat as darker plastic ones. A living ball of moss will stay cooler than a dead one as well, and it will produce oxygen while it's doing so.

Of course everyone should do whatever they want, but to me it makes sense.

 

[Vance Wood]

I think dark plastic would be even worse than transparent because it heats up in the sunlight.

As for the mesh @Paulpash mentions, I can agree on that! Blackbirds are a serious pest in my yard as well, they scoop out entire pots within minutes and they aren't scared to pull seedlings - or even established shohin - out of their pots.

I also agree on the real world implications, lab studies aren't worth jack if they can't be applied. I think we've come full circle with a real world application: air layering. If light has a limited effect on phytohormones, and little to no effect on root formation, a transparent container could be beneficial for multiple reasons. Not only because the sphagnum stays alive and fends off fungi, but also because we can see how far along an air layer is, if it needs more water or not, and because transparent containers don't capture/trap as much heat as darker plastic ones. A living ball of moss will stay cooler than a dead one as well, and it will produce oxygen while it's doing so.

Of course everyone should do whatever they want, but to me it makes sense.

Sphagnum moss has a natural hormone that favors root gtowth.

 

[just.wing.it]

Sphagnum moss has a natural hormone that favors root gtowth.

And it holds water like a champ!

 

[0soyoung]

If light has a limited effect on phytohormones, and little to no effect on root formation, a transparent container could be beneficial for multiple reasons. Not only because the sphagnum stays alive and fends off fungi, but also because we can see how far along an air layer is, if it needs more water or not, and because transparent containers don't capture/trap as much heat as darker plastic ones.

My climate is quite cool, rarely getting much above 70F/22C for daytime highs. I always use clear bags for air layering and sometimes cover them with black plastic in an attempt to raise temperatures and accelerate prospective root growth. It was never clear that it made any difference, possibly because most of my layers are shaded anyway. So I just do a clear plastic covering and call it good.

I also use a split 1 gallon black plastic nursery pot wrapped around a vertical stem, filled with bonsai substrate instead of sphagnum, from time to time. These I water daily whereas I have had to remoisten 'bagged' sphagnum only two or three times in the entire course. I like using bonsai substrate because the adventitious roots are in-situ 'hardened' whereas, 'sphagnum roots' are thick, fleshy, and fragile and need to grow in my substrate for 4 to 6 weeks before leaf drop to similarly 'harden'.

I have and in fact still have some plants in clear plastic pots. The only difference I note is that there is a lot of algae growth on the inside of the pot walls. Maybe more careful analysis would reveal further differences, but I don't care. It has no glaringly obvious effects aside from the algal growth.

 

[Orion_metalhead]

I would say you're talking about two different things--exposure and sunlight. I don't think roots have a problem with light itself. I do think newly sprouted surface roots have an issue with exposure and drying out. Exposed roots are subject to the drying effects of wind and intense sun in the summer. I have also found that a covering of chopped sphagnum moss on the soil's surface after a root prune produces many more roots on the surface and an inch down because it traps a humid layer against the roots and soil, allowing a more even environment....

Do you remove the sphagnum after a certain period or leave it?