Yin and Yang - A Tree's Balance

rockm

Yes and no, depending . You can't make a really accurate guess as to which branch will die off if you prune this or that root. It's impossible with most species, or at least, that's been my experience.

You have to deal with OVERALL balance, rather than concentrating on which branch is connected to which root or roots. "Life" paths, or connecting tissue between brnaches and roots can be quite circuitous in some species winding away around up and down, etc. on the trunk.

There are apparently some exceptions. I've found there is a direct correlation between branches on Bald cypress and roots directly below. If you prune a larger root directly below a big branch on a BC, I've found that the branch slows down, as does any basal "fluting" of the trunk between the two. I've heard there is a similar correlation in collected arborvitae from the Northern U.S. and Canada.

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ripssurf

are there examples of any other species?

thats good to know about BC. my BC will be ready for a trunk chop next year (maybe) and wont be root pruned until at least the year after that. it makes me start to wonder whether or not BC can actually be air-layered...

by the way, how are roots affected during air-layering of say a maple?

jeff

Brent

Once again, understanding some plant physiology can help explain the effects being discussed here and give you some really powerful tools for understanding what you are doing when you prune either the roots or the top.

The foliage and the root tips communicate with each via specific pathways. These pathways are the vascular system, both up and down the tree. The messages are chemical in nature. The roots use the hormone cytokinin to send the message to GROW to the terminal buds and shoots, and the foliage and the shoots send food and the hormone auxin to the root tips to tell them to GROW. This is a self reinforcing cycle, the more the shoots grow, the more auxin they send to the roots, the more the root tips grow, sending yet more hormone back to the shoots, etc.

The terminal buds also send hormone signals that suppress growth of buds, that is why the growth only occurs at the tips. Remove the tips and you stop suppressing growth of the dormant buds. This is how we get backbudding and ramification.

So... if you remove or disturb the roots of a tree, you disrupt the cytokinin signal for the shoots to grow, top growth stops until the root damage is repaired and the cytokinin signal is restored. Meanwhile, the existing foliage continues to send food and auxin to the damaged root system to rebuild it. If you want maximum root repair would you remove the foliage? Of course not, but then we don't live in a perfect world because the roots also have the role of providing water for transpiration in the leaves. IF you can control the transpiration, you can leave all the foliage for fastest recovery. This can mean placing the tree in the shade, putting it in the greenhouse, covering it with a tent, sheltering it from wind, raising the humidity, anything that is appropriate for the situation. There is no easy solution for finding this water balance, it just takes experience and careful monitoring. If it can't be achieved, then you may have to remove some foliage to reduce transpiration. For an interesting application of this principle in root pruning dormant bareroot seedlings see this article:

http://www.evergreengardenworks.com/rootprsd.htm

Now... which foliage would it be best to remove? Should you head it back in general or use some selective method? Obviously, if the root growing signal is coming most strongly from the terminal bud and foliage, you would leave this foliage, or at least some of it and remove the inner leaves. This is counterintuitive because the plant, left to its own devices would shed the terminal foliage. This is because it CANNOT support this foliage from a physical standpoint. When there is a water deficit, it is the margins of the plant that will feel it first, the areas farthest form the roots. We don't have to be limited to this system because we can alter both the environment and selectively prune out other areas.

So, you can think about these systems as being in balance, but it's not really balance we are talking about because nothing is in stasis as balance connotes. The entire system is DYNAMIC. If you think about it in these terms, it is a much more powerful tool. For example WHY does a tree shed its lower and inner branches? This is easily explained using the hormone pathway system. Inner and lower branches are shaded, thus their signal is not as strong as the upper and exposed branches and foliage. So the usual self reinforcing cycle becomes a STATIC cycle. The branches and foliage produce only enough food to keep themselves alive, send little or no food or auxin to their specific roots. The roots, receiving no strong signal, send little or insufficient cytokinin to produce shoot growth. These branches then fall further behind in growth compared to the upper branches and become even more shaded. They will stay alive only as long as they can produce enough food to meet their own needs, but eventually they will be shaded so much that they can't even keep themselves alive. At this point, the roots will begin to wall off the pathways because there is no activity, and the tree will shed these branches.

You can apply these principles in a great many situations that we encounter in bonsai, such as dormant versus growing season root and top pruning to acheive either coarse or refined growth. Learning how to apply the principles takes you out of the cookbook realm of typical bonsai books and allows you to analyze and predict the outcomes for YOUR situation.

For more on plant growth principles see this article at my website:

http://www.evergreengardenworks.com/growprin.htm


Brent
EvergreenGardenworks.com
bonsai@pacific.net

mike_p

Brent, excellent article!

Regards

Mike

__________________
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Man's attempts to improve nature,
Are imperfect.
MP@BBB Studio

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Will_Heath

Wow, that's what I meant to say, lol.

Excellent use of words Brent and fantastic information, thank you. It is very nice to see intelligent discussion on these matters.

Would you then suggest the same treatment for deciduous and conifers even though both have the same inbuilt dynamic balance? I do not think so because even though both are the same in many ways, they respond differently.

Any branch that is not producing enough to support itself will be cut off and left to die, energy then being diverted to those that can. I understand this but when you mention that some foliage should be removed if the conditions to prevent transpiration do not exist, I get a little confused. Is it not just a guess as to what foliage to remove and how much? Your statement on removing the foliage farthest from the roots is brillant, but how much and which?

And lastly, you spoke of balance as not quite an adequate description as the tree is not static. However I am sure that you will agree that the crown often mirrors the roots. In fact many people will not use jagged particles in there soil mix for maples because they claim it causes jagged, ungraceful branches that mirror the roots. It has also been said that if All the roots on one side of a tree are removed then most the branches on that side will die. You have also agreed that a tree will try to push root growth and stop foliage growth when root pruned, in order to "balance" the roots to the foliage again.

All these things leads me to still believe that a tree has a balance that it strives to maintain. I'll leave it to your vast experience to say how, but I think we will agree that there is indeed a balance inbuilt for trees. Or maybe we should refer to it as "Dynamic Balance." (Coined by Brent)


Will

rockm

Brent

Just when I post some vague fuzzy observations, you come along with all this, this FACTUAL Scientific stuff... Thanks. As always, I can take alot away from you've posted.

Attila

Thank you Brent for reminding us
that we should look at the the roots and foliage as parts of a system in which the healthy components will try to repair the damaged components. The roots do not always initiate the process (see the cutting, where there is no root at the beginning) and neither does the foliage (see the stump where there is no foliage).

Once we understand that the foliage sends signals triggering root growth and that the root sends signals to the foliage to grow, and all this happens only if there is enough water to keep the foliage alive, keeping this cycle going is as much art as it is science. That's because too much of one thing can be as damaging as too little (too much foliage leads to too much perspiration, but too little of it will starve the roots).
We can certainly help by providing an optimal environment for recovery.

Brent

I'm not really recommending treatment, that is what I am trying to get you all out of. Rather I am pointing out how the systems work so you can design your own plan and work intelligently. Some took you to task because you made recommendations without considering all the factors (by the way, I am not one of them). What I am saying is that if you use the principles of plant physiology, you don't have to use any disclaimers, cultural and environmental differences will be obvious and part of the solution.

Fair question though. Both conifers and deciduous plants operate using the same principles, both use cytokinin and auxin. The differences are subtle but important. Conifers (and other evergreens) retain their foliage year round and thus are subject to at least some transpiration while dormant. You have to take this into consideration when root pruning. Root pruning a deciduous plant when dormant gives you a free pass (see the article on Pruning Dormant Bareroot Seedlings cited). No foliage, no transpiration. The extent of root damage will determine how many buds can be supported, only those buds that can get water from the roots will open. Absent unusual events (e.g. sudden heat waves) the plant automatically adjusts foliage growth to the amount of water that can be provided. Conifers are different. When you root prune, they will face full immediate transpiration load dependent on temperature. Therefore you have to be much more careful to reduce transpiration. Otherwise the pathway system is intact and leaving the maximum amount of foliage will give you the maximum amount of root growth. I have root pruned thousands of dormant pine seedlings of various sizes using various top pruning and root pruning techniques. The principles I outlined works, leave the greatest amount of foliage you can, and leave the terminal growth, especially the center candle.

Conifers are also different from deciduous plants in that their pathways are more specific. This is probably because they are more primitive. Deciduous plants have a great deal more 'crosstalk' BETWEEN pathways and faster cross connection formation. You also need to maintain some foliage to insure that that the roots won't wall off a branch for conifers. This is also a primitive feature. We call it 'keeping a sap line', but it is still a result of the physiology I stated modified by the slowness of the response in conifers. Conifers have banked their evolutionary bets toward specific dormant bud formation at the nodes. Break a branch and the growth starts again at the last NODE remaining, giving up the nodeless stick. Deciduous trees have evolved to have much more active and faster acting buds. Break a branch, and yes you bud break at the node, but break a long internodal segment and you can usually get internodal bud break as well. The degree depends on the species of course.

So, where you (I perceive) are trying to get me to say the two realms are different because they behave differently, I see it as acting according to the SAME principles, only somewhat modified by their genetic evolution. The outcomes are still predictable using the principles. The more the world is the SAME, the easier it is to understand. If we have to make up new rules for every species, as is usually done in bonsai, the more difficult it is to UNDERSTAND and function universally.



At the risk of just being semantical, that phrase of 'diverting' or 'balancing' energy or resources has always bothered me. People throw it around as if it really was the way things work and as if it explained everything, such as "Oh, you just remove the lower candles first and the upper candles later to redirect and balance the energy" (I'm not taking you to task Will, but I see this a lot). Well, that really doesn't explain anything. When you see the WHOLE system, then you begin to understand why you want to do that. The ENERGY doesn't come from the roots, only water and minerals and hormones come from the roots. Roots are net consumers of energy. Leaves alone produce the food for the whole plant, feeding themselves and the roots and precious little of that food ever goes back up the stem. What does go back up is cytokinin and a water solution that direct growth to specific areas by triggering bud break and shoot formation. Now you can redirect that growth by redirecting the signal, but it is still the leaves, especially resulting new growth that fires the resources. See the difference?



Sorry, if I gave you that impression, it is not correct. I am saying that IF you have to remove some foliage to limit transpiration, you can be creative about it and remove the foliage that will ONLY limit transpiration without diminishing the auxin signal significantly. So, it's NOT a guess as WHERE to remove the foliage, but yes, it is a guess as to how much to remove. I think I made that pretty clear. It is a matter of experience and sometimes even luck depending on the weather. I have no easy answers about how much to remove for EVERGREENS and actively growing deciduous plants, however, I give you clear answers for dormant deciduous plants in the aforementioned article.




Boy, you are scratching a raw nerve with that one. One of the great all time myths. YES, the top of the tree does sometimes mirror the roots. But the explanation for this is so far off base as to be ludicrous. Sharp particles have absolutely nothing to do with this. Plant roots tips don't 'divide' when they hit sharp particles, even razor blades, they go around. They branch just like the top does by 'budding' behind the tip. Root tips CANNOT divide, it's now how roots grow. Grow a tree in soil mix that is very coarse and aerated, even packed with broken glass and the roots will be nice and FAT. Grow plants in dense fine sand that is perfectly rounded smooth spheres and the roots will be fine and numerous. It has nothing to do with sharp particles, it has to do with the density and aeration of the soil. In a fine, poorly aerated soil, roots will grow small and numerous to create MORE surface area to be able to get enough oxygen to live (actually that's a bit anthropomorphic, in a GOOD soil, that can grow fat because there is plenty of oxygen). The top mirrors this because it is much EASIER to get ramification, especially FINE twigs if you have poor growing conditions. It's as simple as that. You notice there isn't much talk about sharp sand these days. Growers now realize there are better ways of controlling growth and ramification using GOOD soils.



Now you are getting anthropomorphic. The tree isn't trying to balance anything, it is responding to hormone signals. Shoot growth stops after root pruning because it no longer is getting the GROW signal. It is not a response, but the lack of one. The auxin signal is still there so the root repair growth proceeds. As for the issue of specific pathways, it depends on the species as I said above, but usually there is enough 'crosstalk' among all species that branches usually are NOT shed in this situation, but it is a possibility. It is much more likely that many roots will die on the side that has had a trauma with the branches broken off. The result here in high mountain conifers is create a shari along the former 'lifeline'.



If the balance concept helps you to understand the principles, then that's cool, at least you are analyzing the situation, but I still maintain that the tree doesn't 'TRY' to do anything, it is simply responding to signals and forces. I think this is a cleaner way to visualize it, but in the end it may be all just be semantics. The important thing is to understand the SYSTEM to the degree that you can predict outcomes, then you aren't chained to the bonsai cookbook system, which sadly, most of us still are.

Brent
EvergreenGardenworks.com
bonsai@pacific.net

BrianBay9

Brent, you're posts here have been a great help. Thanks.

Brian