How do you recognize a node?

Looks like all this discussion shows the huge range in definition arborists have for the same word. This is where we need to unify so we can communicate effectively between each other. I'm not being critical. I'm still reading up on this and learning. What do we really need to know? Cuts are better at nodes where there's more buds. Cuts are not as good, but an option at axillary buds? Meaning the ones between nodes on the side of a shoot. Nodes are better cut points than adventitious buds. Meaning the buds that are dormant and hidden and between nodes.


Sent from my iPhone using Tapatalk
 
How do you determine the growth points if no sprouts or buds are evident? (from a 4-year old)
Excellent question: Let's start with basic botany. At the end of the tree's growing season, a terminal bud is set, and a wrinkled collar is formed. This 'bud scale scar' or 'bud collar' goes all the way around the twig.

The bud collar marks the location of the terminal node, and the accessory buds around it. (The distance between these bud collars is the 'internode'. Measuring this distance is a common method of assessing condition and growth rate.)
Cutting just beyond this bud collar cuts off the downward flow of the growth suppressing hormone called auxin, and stimulates the dormant accessory buds to sprout and grow.

Sometimes in older branches the bud collars are not visible. Buds are most reliably indicated by a reduction in branch diameter, or 'taper'.
Buds are also indicated by bulges and bumps that do not go all the way around. These formations may be due to a buttress forming at the base of a lateral branch that has been shed or removed.

Buds are also preserved at leaf scars, which are growth points that are not associated with the terminal bud. These buds were formed at the 'axil', or base of the petiole that supports the leaf, so they are called 'axillary buds'.
Cutting just beyond axillary buds is better than cutting to no buds, but cutting just beyond dormant buds at terminal nodes provides the best chance for wound closure and sustainable regrowth."

Kevin, I reread your 2014 piece and think the above aligns with it. I find the term 'adventitious bud' most confusing. Would you agree that most adventitious shoots sprout anew, de novo, out of meristematic tissue? If the new adventitious growth stops sprouting long enough to form enough structures, that might be called a bud.
But most of the early adventitious growth does not seem to involve bud formation; the order is, shoot-leaves-buds, right?
"Buds are preformed structures..." as you conclude in your article.
 
Last edited:
With respect to: most of the early adventitious growth does not seem to involve bud formation; the order is, shoot-leaves-buds, I'm not sure what is meant by "early" or to what the "order" refers. Maybe I'm not paying enough attention to earlier comments on the thread. Indeed much adventitious sprouting does not involve bud formation. Sometimes it involves long-maintained meristematic points, other times meristematic points formed and sprout right away. I don't know about proportions. Sure, much of the adventitious growth is associated with woundwood or callus (using the term in the strict sense).

I'm not comfortable at all with restricting nodes to the bud traces of accessory buds at the bud scale scar. No botany text or dictionary except Shigo's defines it that way. Sure, it is glossed that way now by his adherents, especially folks who got most / all of their botanical information from Alex. This is an example of how he came about to write New Tree Biology Dictionary which initially was a separate, free-standing book separate from A New Tree Biology. And also why those were self-published. I think I've related my version of that genesis story in these pages. He wanted words to have more narrow or specialized meanings than in common or academic parlance. Look at vigor/vitality or capacity/ability. "Nutrient" is another one. No one else limits them that way. Now for those latter terms, how I deal with divergence from my old friend and project leader is to personally try to avoid their use.

Hard to avoid "node" though! I'm not telling you or this community how to define stuff. You should do what is useful to you. For me personally, having a two-tier system of terms, one for plant science and horticulture professionals and one for professional arborists is just too wearing. In real-world evaluations, branches derived from accessories might well have special value! But laterals formed from axillary buds would still be nodes to me.

And Guy, I do know that we are in sync with 99% of this stuff! Maybe 100% after we get past the terms!
 
KTSmith, as I'm writing this, I see you just posted but I could only see the beginning of the post. Please let me know if the assumptions I made are correct in terms of botany.
This discussion has got me thinking a lot.
Reduction cuts, removal cuts, and how the two relate to nodes and terminals.
Redirection, subordination, and favouring.
Strong stems after reduction applications?
In an attempt to influence the leading edge of a crown, I think being aware of this stuff is helpful. And structural pruning is mostly about influencing the leading edge imo. It's more about changing what the tree WILL grow into. It's less about changing what the tree HAS grown into. Change has to come in time in order to be beneficial. The instant fix we often seek in today's world is often a problem. In pruning, an attempt to 'correct' structure with one pruning application that is too far gone, will often result in further problems as large as the initial problem. Breaking more than fixing. Cutting a solitary girdling root might be the best way to instantly 'fix' a tree. If fixing means vitality and longevity.
Do we make enough tip type cuts? Why do we generally try to avoid removing main terminals? Is it to avoid changing natures course? A tree has no main purpose of quality or longevity. It has main purpose of winning the competition for light and then to reproduce. In civilized areas we need to sway this nature of competitive, speedy, vulnerable growth. We need to sway the tree towards structural quality and longevity.
I believe the most important cuts are the bigger ones, often reducing or removing the 'head' of a stem. I think many try to avoid 'heading cuts'. Or more likely we use the term incorrectly. A 'clean' head back cut is really a reduction cut. In order to best serve the tree I think a RANGE of cut diameters should be made, having no bottom end. For example, 'cuts up to 2 inches will be made' not just 'cuts of 1-2 inches will be made'. If the prescription objective demands drastic change by reducing codoms or reaching limbs or complete crowns, then smaller tip type cuts are also important, to compliment larger cuts. Both removing shoots grown from terminals and/or removing shoots grown from axillary buds. These tip cuts can significantly influence the leading edge. Hormones can be affected. Dominance can be swayed. More light can stimulate growth further in.

So here are four assumptions (I think correct?) in order to help in the following text (and previous text).
-in maple (opposite pattern) there is an axillary bud on either side of the terminal bud.
-there are also axillary buds along a section of stem between nodes.
-a reduction cut is removing the larger stem at a node. Applied in reduction and structural applications.
-a removal cut removes the smaller stem at a node. Applied in thinning, reduction and structural applications.
Sometimes in maple, an axillary bud will dominate over a terminal. This makes a great future reduction cut as it is not a terminal cut, and maintains stem direction continuity. More often, reduction cuts involve a terminal stem cut that creates a turn or elbow, unless it's made at a small diameter where a bend can react and straighten. It's amazing how trees can react and seem to 'flex' stems. But the biggest cuts in a reduction application are often 2-4 inches, usually leaving a permanent bend. Unless the reduction cut was temporary, and the removal cut further in is made in time.
Perhaps a good way to look at pruning techniques is by the years of shoot removed. One years growth is one internode or its the stem section between two nodes. The bigger cuts are often the removal of four to eight years of stem growth. I think Guy referred to some way of doing this using annual rings.
Often with tip pruning a whole year or whole internode is removed. Or several years or internode sections. So is a node the point at which an annual growth ring stops?
I only use an internodal cut rarely. Like when I'm attempting to invigorate by reducing shoot growth, but maintaining foliage levels in a stressed tree. (Late winter app). I think an internodal bud cut is more of a problem as diameter increases?. Like when cutting into 4 inches of wood with less than 1/2 inch to dominate. But sometimes that may be the best option in the right context.
Is pruning more a question of diameter size and proportion? (As opposed to nodal vs adventitious.) Proportion meaning the ratio of cut stem to remaining stem diameter. Having said that, good proportions for pruning cuts are more likely available at nodes. For this reason I think most of us are already using nodes as pruning sites for the most part.
Also, pruning could be more about opportunities and the lack of a great option?
In a sense, a tree has only one original terminal. More obvious in softwoods. But a terminal bud is any leading tip on the tree. So the tree and its future can be influenced by changing the terminal makeup.
How does the term 'apical' fit and should it replace 'terminal' at times to correct what I'm saying to mean what I'm thinking?
So?
-a reduction cut involves the removal of one or several complete sections of internodal stem.
-a reduction cut usually involves the removal of a stem that once arose from a terminal bud.
-a removal cut also involves the removal of one or several sections of internodal stem, but usually involves cutting a stem that arose from an axillary bud.
I think this thread helps with the issues of terminology and how we practice. It's not easy to put words to what we practice. But we do need to improve communication around this. Myself included big time. And above I'm half preaching and half speculating. Let me know where I'm wrong here.
When we tip prune we might be slightly internodal, knowing the small end will dieback and fall off. But at times we need to make cuts that aren't perfect. At small diameters under 1", it matters less. So much detail can be missed when we avoid these cuts because we can't reach them well enough to make them perfect. Lately, I've made more reduction cuts to make the next bud below the cut at a node. But still not always.
Thanks for reading this edited thinking out loud. Isn't that what most writing is?





Sent from my iPhone using Tapatalk
 
Last edited:
"With respect to: most of the early adventitious growth does not seem to involve bud formation; the order is, shoot-leaves-buds, I'm not sure what is meant by "early" or to what the "order" refers."
Chronological order, in general terms.

"Indeed much adventitious sprouting does not involve bud formation." Yes thanks that was my main point; no bud scales present. Which really limits the occurrence, and relevance, of adventitious buds.

I'm also not comfortable at all with restricting nodes to the bud traces of accessory buds at the bud scale scar. Who would suggest such a thing? Not me! ;)
All growth points are nodes. When we see traces of the terminal bud collar or scar, or other positive signs, it may be logical and useful to call that point a 'terminal node'. There is a need here for these words (or another, more apt phrase?) to define a more narrow or specialized meaning than in common or academic parlance. It's technical jargon, if you will. Do you think the botany texts would shy away from including this differentiation? Are you sure it's not mentioned in any? The concept of these basic structures probably applies to more than pruning.

I agree that the vigor/vitality or capacity/ability dichotomies don't work, because they lack a qualifier. 'Genetic vigor" is similar to 'terminal node'; carrying the necessary meaning, without changing the root word.
Unless a newly minted arborist is within earshot and is primed to correct grammar, I'm comfy saying 'Vigorous' to a client, instead of 'in high vitality', without worrying about confusion with genetics. But yes we can get too semantic at times; a lexicon must be flexible.

Kevin i hope this crystallizes the clarity on usage of 'terminal node', and gets us back to 99.999% agreement! Does this distinction make sense to everyone else?

Ryan yes i agree that 'terminal' may be synonymous with 'apical', meaning 'the tip of a branch, (where at the end of the growing season a terminal bud will be set).' And yes the biggest cuts are the first to plan, as Henry Davis prescribed (May 2003 TCI):
●● Objectives: safety, survival, aesthetics
●● Inspect structure
closely, and at a distance. Consider
supplemental support systems
●● Locate dominant leaders, and an ‘inner
crown’ to be left intact
●● Choose 4-10 large branches that could
be reduced or removed
●● Start pruning from the top down,
heaviest side first, tips last
 
How to recognize a node? Start small and slow, by reading twigs. Dr. Coder wrote 2 CEU articles on twig anatomy, Feb and April 2014. You can still take the test for credit on the latter one--if you get it in tonight!

Locating terminal bud scars is the key to finding terminal nodes. Start small and slow with twigs, and it'll be easier to move up to branches.
Taking the tests was a great reviewing experience for me. Dr. Coder is a pedagogical powerhouse!
 

Attachments

  • wb live oak growth rate.webp
    wb live oak growth rate.webp
    71.1 KB · Views: 18
  • Like
Reactions: joe
Yes, Kim Coder's articles are definitely useful.
I do have qualms about the advocacy of using the term "node" as referring to the position of terminal buds rather than axillary buds. That might seem to be purely an academic point. Folks should just be aware that the rest of botany and horticulture use the term in a different way.
 
What made Kim's article most useful to me was to see that his description of tree anatomy largely agreed with yours!

But where is this advocacy that you keep referring to, of using the term "node" as referring to the position of terminal buds only? The main--only?--advocate for this usage has passed away. Is using 'terminal node' for these positions okay, or would another phrase be more effective at differentiating these vital features?

Folks should be aware that the order set in Dr. Shigo's Pruning Rule #1 was correct 28 years ago, and is still worth following today: "Pruning cuts should be made at (terminal) nodes, OR at lateral branches." When confronted with a codominant, arborists usually follow an overgeneralised 'rule of thumb' and make a big sloping cut, where there is no collar, and rot is likely.
Or they can follow the 1986 training by Shigo (and later from Dujesieffken et al) and make a smaller wound by reducing the codom to buds at a terminal node, where wound closure is much more likely. Of course it's preferable to have lateral branches present at this terminal node, but I agree with Shigo that the size of the remaining lateral should NOT define proper pruning.

The size of the wound, and its closure, matter much more.
 
Last edited:
To further confuse the situation, see the Epicormics article in the April ArbNews.
In the *only* independent reference the article
cited, I found this graphic
http://treephys.oxfordjournals.org/content/early/2012/05/03/treephys.tps040/F1.large.jpg

It seems to assume a second flush after one terminal bud scar is made, so there are not one, but two rings per year. (This is getting to be too much like counting false rings in the xylem.) I thought this was an exception, but it's presented as the rule in the Meier article. The Moore article that all epicormics come from dormant buds, though Meier describes adventitious formation of buds. Why the selectivity??

Kevin, do we need these 4 new terms herein and henceforth established by fiat: "Therefore, we propose that all vegetative buds and meristems on old growth units be called epicormic buds or meristems (sensu Burrows 2000,Del Tredici 2001, Gordon et al. 2006, Colin et al. 2010a). Groups of epicormics originating from an original epicormic bud should be referred to generally as epicormic complexes (Table 2). Individual units within a larger feature, such as organs within a bud or buds and branches within an epicormic complex, should be considered epicormic components. All the individual components associated with a given feature will be referred to jointly as the epicormic structure. The combination of all epicormic complexes on a tree will be called the epicormic composition (Colin et al. 2010b). Changes over time in the characteristics of epicormic buds, complexes or composition will be called epicormic development"

"Generalized shoot of an oak with different bud types and growth terms identified. All buds are sequential buds with the exception of a and g. Letters identify the following: a, terminal bud; b, collateral accesory bud; c, sequential bud; d, leaf scar; e, cataphyll or bud scale scar; f, cataphyll or bud scale bud; g, sequential branch; h, secondary accessory buds; i, bud scar formed following the death of a sequential bud. Drawn based on Heuret et al. (2003)."
Meier Epicormics twig image.webp Meier Epicormics twig image.webp
 
I began to read that April ArbNews article earlier this week but I quickly glazed over. More my fault in starting it tired, rather than the article itself. Before I comment too much, I need to read that and refresh myself with some of the other pieces you cite. I know I'm pretty slack in giving proper references in ArbNews and TCI articles. That's probably not good...some readers such as you and me are interested and well-equipped to deal with primary sources. I did see that Tree Physiology article when it first came out, but I likely need to reload it into my thinking. In the image you attached immediately above, I agree with you that having more than one terminal bud scar should be the exception, not the norm. I need to read the articles fully before commenting further on the image.
 
From Shigo's Dictionary: "It is important to recognize nodes and internodes on trees because this is the best way to determine the type or position of a pruning cut. Cuts are either at internodes or at nodes. Pruning cuts that are made at nodes cause less injury than cuts made at internodes.
Crowns of maturing trees may be reduced by a number of branch and leader stem removals.
Make certain that all cuts are at nodes; if possible space the pruning over a few years."

coming up for air yet Kevin? That Epicormic piece really confused the heck out of me. Lost in translation from oz-speak?
 
KTSmith said:
What does a practicing arborist recognize as a node on a tree stem or branch?

Botanically, defining a node is simple and based on primary growth. In the seedling or newly emerging shoot, growth is from cells produced at the tip by the apical meristem. Based on the genetic program, a leaf is produced every so often and in a specific arrangement. In the leaf axil, the upper side of the angle between stem and leaf, a bud is formed. Let’s call that an axillary bud. The node is located at the connection of stem and axillary bud. The length of stem between nodes is termed the “internode”. Yes, very creative.

Okay then, the axillary bud breaks dormancy and produces a new shoot with its own tip meristem. In woody dicots (“regular trees”) the vascular cambium forms and “secondary” growth ensues in branch and stem. That branch is certainly located at a node. Now not all of those axillary buds germinate and sprout. Some cells divide just beneath the bud base and move the bed along outward in the bark, just to the outside of the stem vascular cambium. It can be mighty hard to see those latent buds, but they are still at a node. There is still a “bud trace” in the wood that shows that these are axillary buds.

As the stem or branch increases in girth due to wood production, new buds may form along the stem surface at locations other than nodes. These are defined as adventitious buds. There is no bud trace, there is no node. Sometimes meristematic points are formed without the protective scales characteristic of buds. These adventitious buds and meristematic points may or may not germinate and sprout right away. They might just continue to divide and be embedded at or beneath the bark for years and then sprout is response to stress. Tree survival after, say, storm injury depends on sprouting from both latent axillary and adventitious buds.

My sense is that when I hear an arborist say to make a reduction cut to a node, she means to cut back to what would appear to be a strongly attached branch that is assumed to be derived from an axillary bud. I’m not quibbling with that assumption, at least not yet. I’m just trying to figure out how you folks use these terms.
Click to expand...
I'm replying before reading the entire thread here...but this takes me back to a thread (exactly which, I can't recall) in which I was asking Guy how to recognize a node on larger diameter wood.

The reason was to make good descisions when considering leaving a long stub following storm damage. This would be in hopes of new growth forming at the cut and training a new branch, rather than removing the entire damaged piece.

While I realize that growth extension may vary from year to year, I like to think I can use those observations along with other cues to find what may be a decent node.

I remember a conference lecture dealing with the training of one rather large tree branch. The speaker had asked the client if they were willing to leave a stub in hopes to retrain a branch rather than introducing a large cut at the trunk. The clients agreed and the branch was worked on over several years. The new "branch" fits right in with the rest of the tree and truly maintained the overall balance and aesthetic value of the tree. I have never looked at storm damage mitigation the same, since.

Locating nodes can be a big part of good damage mitigation and reduction pruning, and certainly this thread can apply. I feel this is a valuable topic and hope to learn from what follows here. Thanks for posting this!
 
The best answers to the original question might be:

1. Look for buds. (A hand lens in the medical bag with the bandaids is very handy!) For reference, they are visible in the pics with the pith trails.

2. Look for terminal bud scars.

3. Look for a change in diameter.

4. Look for other signs of buds: bulges, wrinkles , etc.

It was good to reread your article; busting the myth that there is a collar at the origin of every branch, or even most branches: "The vascular cambium is continuous over the surfaces of branch and stem as well as the union of codominant stems. There are key differences, however. Early in the growing season, branch wood forms first, followed later by the formation of wood by the stem. This alternation helps produce a strong branch collar of interlocked branch and stem tissue that provides good structural support (Shigo 1985). Also, the inserted base of a branch contains wood that is chemically modified to resist the spread of infection from the branch into the stem. The union of codominant stems does not produce such interlocking layers and does not contain the protection wood."
 
Cool discussion. Kind of difficult to implement, since it applies to storm damage more than anything else that isn't everyday reduction pruning... When I prune storm damage, I'm often in 6"+ diameter wood, looking for anything odd-looking that might indicate a different mode of growth. Since the cuts can be so big, I also often cut straight across instead of on the angle. Also, I tend to leave more wood as I get further into my career - especially vertically cracked wood (with permission of the tree manager).

I have generalized degrees in biology that lead me to have a lack of botanical physiology knowledge and a fair breadth of knowledge about how other multicellular organisms grow and "apoptose". When I combine my five years of work as a dedicated arborist with my schooling, I tend to see trees on a spectrum far away from humans (our implicit reference point even though we don't like to admit it...) and more towards bacterial colonies, which often have unspecialized, two-dimensional growth. Obviously, it's not that simple and the departure from bacterial growth patterns is substantial, yet placing it as a contrast set with humans is a useful exercise in freeing the mind.

Some work I did with Dictyostelium discoideum, a slime mold that exists as single cells, aggregates, and then subsequently exists as multiple cells with some specialization leads me to expect/suspect tree biology to be more plastic than is oft given credit. Sometimes, I feel that the science of tree biology points to plasticity, that we know it does, and that we still get hung up by expecting hierarchical physiological patterns such as distinct, irreversibly-fated organs/tissues, and three-dimensional growth. It seems to me that trees have enough indeterminate capacity to do almost whatever they want.

I'd really, again, like to emphasize my lack of in-depth knowledge about plant-specific physiology.

Back on the applied side, I think it's most important to provide care over time for storm damage instead of one-offing, and to find a node/irregularity if it's possible and not worry about it if it's not possible.

I gave a day-rate quote to travel and prune several southern live oaks last month. Got there and the main issue was the one growing over the house. It had these internodal 12" decayed heading cuts with tight clusters of 4" diameter, 15'-long branches... Two problems I had were 1.) climbing past the sketchy attachment points to reduce, and 2.) setting my hook for traverses between leaders. I had one chance to throw because the acute junctions prohibited retrieval, then I had to trust the attachment for the duration of the traverse... I explained the situation to the manager and am returning with a narrow access bucket to finish up that part of the project, to thin and reduce the new growth. In this case, I am repairing negligent pruning, but it could have been storm damage... I feel like the live oak is recoverable, but it will take several pruning cycles before I would recommend allowing the new leaders to grow out over the house...
 
It really applies to ALL reduction pruning; it's just needed more often after storm or saw damage.

What kind of pole tools do you use? I can't imagine needing a lift, ever, though they can come in very handy!

But you're right about the plasticity of live oaks; see the thread about Lot-Line Pruning. Sustainable regrowth has arisen from the internodal cuts.
 
guymayor said:
It really applies to ALL reduction pruning; it's just needed more often after storm or saw damage.

What kind of pole tools do you use? I can't imagine needing a lift, ever, though they can come in very handy!

But you're right about the plasticity of live oaks; see the thread about Lot-Line Pruning. Sustainable regrowth has arisen from the internodal cuts.
Click to expand...

I do not generally use pole tools at height because I like being close to the cut and can typically get there. I'm willing to reconsider it since I got shut down a bit by this tree. Additionally, I have targets below this tree (strung Christmas lights, gas grille, etc.), so even a 1" diameter branch can't be let fly. How do you retain and lower stuff that you cut with pole tools? T-Rex head on a stick? :) I might be able to execute the pole tool strategy with some help from you on that...

I worked one of the leaders over the house, ziplining out a few thinned 4" diameter sprouts. Since it's a prune, one got hung up of course, so I had to haul it up, disassemble it, and chuck it... I did not want to climb past the attachments on the rotted stubs, so I could not get out to where I had several reduction cuts to make after I was done thinning. I was 6' short. Additionally, the hook placements for traverse were difficult, and I had several more to do. The resprouted tops are like tangled brooms, so it is also hard to achieve position upon arrival - it's like climbing around the bottom side of a cage ball with things sticking out. I even ran into dead 4" sprouts (again, over targets). I'm also installing bracing and cabling at a 30' high acute crotch. Basically, the tree is a large hot mess on that side that is very inefficient to climb in. I'm used to doing a canopy per day and this one would take me a few days, including work that I consider a bit hazardous since I would pendulum swing back to my TIP - or get stuck - if the sprouts broke off.
 
You must log in or register to reply here.

New threads New posts

Back
Top Bottom