How do you recognize a node?

Discussion in 'General Discussion' started by KTSmith, Mar 11, 2015.

  1. KTSmith

    KTSmith Well-Known Member

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    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.
     
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  2. Tom Dunlap

    Tom Dunlap Longest registered member

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    Hmmm...now I'm thinking about what I say

    Right now I think you captured the way I speak of nodes in your last paragraph
     
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  3. treehumper

    treehumper Well-Known Member

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    KT, could you post some pics that illustrate what you're describing? That would be a big help. Like Tom, your last paragraph is really the way I'd describe it. If I could readily identify the other nodes then it could help immensely in storm damage situations or dealing with ornamental trees.
     
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  4. JeffGu

    JeffGu Well-Known Member

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    I confess, I'm in this group. I'm also interested in pics that show the differentiation between nodal branches and those that are not. This is quite interesting!
     
  5. guymayor

    guymayor Well-Known Member

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    Welll, where to start? First I agree that many arborists (even one True Professional of Arboriculture near Toronto) unfortunately missed Dr. Shigo's descriptions in A New Tree Biology, and still identify nodes with laterals. I polled authorities in 2002 when I started down the node road, and about half agreed that node = 'place where terminal bud was set' as Shigo termed it. Others such as Dr. Chaney at Purdue said it was any growth point, as you describe above, where axillary buds are formed.
    For practical purposes, I shy away from the conflict, but in the field I look at 'terminal nodes' as preferable pruning locations, as there are likely to be more and better formed buds there. On mature Q phellos for instance these are about 6" apart, or the Q falcata in the pic.

    Visualize that branch without the laterals. the bulges and wrinkles indicate nodes, and dormant buds

    Attached Dendro tale gave me a chance to explore phyllotaxy, " the genetic program, a leaf is produced every so often and in a specific arrangement. " Guy Sternberg of Starhill Forest Quercetum (worth a visit!) was my guide.
    But those nodes are not as cool as Alex's 'terminal nodes'. The accessory buds around the terminal bud are more likely to be innately endocormic, with strong pith trails inside the core, endo-corm, as seen in this tropical table top. pith trail small.jpg red oak sprouts small.jpg
     

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  6. KTSmith

    KTSmith Well-Known Member

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    Thanks Guy for the photo of the bud trace which I think is characteristic of what you call an "endorcormic" bud or branch. I tend to discourage making up new words when there are plenty of good terms already available, but whatever one finds useful, I guess. I also have a bud trace and latent bud on the second page of my little TCI article here:
    http://www.fs.fed.us/nrs/pubs/jrnl/2014/nrs_2014_smith-k_002.pdf and the image is attached to the post.

    I remember someone on the forum quoting someone else that "we know nothing about biomechanics". That's a bit strong for me, but I'd agree we'd be better off we knew more, to be sure. But do we know that the presence of a bud trace confers greater strength of branch attachment? I don't think so. I think we know that all other things like included bark and size being equal, that branches with more years of overlapping collar are more strongly attached than branches with few years. But does the branch trace contribute to that? Doubt it.

    What I described as a node in the early part of the post above is simply what any plant anatomy text from Buscgen & Munch, to Esau to Eames & McDaniels to Kozlowski to Zimmerman to the International Association of Wood Anatomists would call a node. Yes, Shigo did like to emphasize the accessory buds at or near the terminal buds as producing stronger shoots. I think we can see that empirically . But any traditional anatomist would hold that nodes are determined by the primary leaf axils.

    What does this have to do with practical arboriculture? Well, the prescriptive guides use these formal anatomical terms. So I asked the tree buzz community how they recognize nodes. What I was trying to sort out with the original post was how much you folks line up with formal, classical anatomy and how much gets the "broad brush" treatment.

    In my pre-publication review of Shigo's 1984 Annual Review of Phytopathology paper (the best primer on compartmentalization), I sniffed at some of his deviation from traditional uses of terms and commented that if he insisted on using established technical terms in non-traditional ways, he needed to write his own dictionary. Of course, in a couple of years he had done so as part of A New Tree Biology. I'm not taking any credit, I'm actually embarrassed at my taking him to task, but that was my role as a postdoc. Al was trying to unravel some of the bud trace story in his last field season before his Forest Service retirement. I remember gangs of young people splitting bolts and shaving radial planes with razors, looking for bud traces. He found bud traces but didn't find what he was looking for before the clock ran out.
     

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  7. guymayor

    guymayor Well-Known Member

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    "A node is the position on a stem or trunk that was occupied by the terminal bud…Pruning cuts should be made at nodes, or at crotches"Dr. Alex Shigo, A New Tree Biology


    Kevin, this would have been simply resolved if you'd agreed to submit your question/comment back in August 2013 for Arborist News. But an expanded version might be a good exercise, so here we go:


    "the bud trace which I think is characteristic of what you call an "endorcormic" bud or branch. I tend to discourage making up new words when there are plenty of good terms already available"


    First, 'endocormic' had been in use in Australia and Hong Kong and the UK, independently, so I shan't take credit or blame for coining a commonly used, and much-needed term.

    This is a lumping/splitting question. "Endocormic" is needed because "epicormic" was applied to several very different phenomena.

    Growth from a dormant bud releasing is connected inside the core, endo-cormic.

    Growth from parenchymal tissue, at axillary points or not, arises from outside the core, epi-cormic.

    Both types of growth were formerly called ‘epicormic sprouts’, and considered undesirable after utility pruning, or by foresters who wanted wood with no knots. Endocormic sprouts were particularly reviled by vegetation managers, because they grew back toward the electric lines much faster. Endocormic sprouts were particularly reviled by foresters, because they made bigger knots.


    But for these very same reasons, endocormic sprouts are most valued by arborists, who want rapid, well-anchored growth. Are you with me so far?


    We have ecto- and endo-mycorhizae, right? Endocormic is not made up or hard to follow, no like saying 'gyre and gymble oer the wabe', or 'The answer is blowin' in the wind'. As a forester informing arborists, Shigo named the concept, and described its importance. It’s up to arborists to break the chains binding us to our profession’s background in forestry and vegetation management. We must use the knowledge that Shigo gave us.


    "I also have a bud trace and latent bud on the second page ..." I see that, nice, but who writes those captions? What Shigo called "compacted xylem" gripping the bud trace is called "distorted". Why use a pejorative term? This inherent put-down reminds me of risk assessments that discount the extraordinary strength in woundwood and knots and burls because they are not ordinary, but 'deformed'. Tree growths are beautiful, even when they don't meet the forester’s ideal.


    "I remember someone on the forum quoting someone else that ""we know nothing about biomechanics". That's a bit strong for me,..."

    Way too strong for me, too. That's because your recollection is incomplete. I quote Dr. Ed Gilman (with his OK) who said "we know next to nothing about biomechanics" Deleting the qualifier creates a corporate-style strawman fallacy, easy to knock down. I’m sure that was an accident though. ;)


    I like quoting Ed, who also said, "“In Sweden, 600 to 800 year old trees have been reduced for hundreds of years. They have 4 or 5 foot trunks – some even larger – with 4 inches shell wall. We remove too many trees and prune too few!”, so I go over there every summer, to work and learn what is steadfastly denied in the US. But that's another story...


    "...do we know that the presence of a bud trace confers greater strength of branch attachment? I don't think so...."

    O good sir I beg to differ; having hung my aspirations for survival for my entire 'adult' life on slender branches in the tops of trees, I do not discount that attachment, nor its strength.

    Which gets us back to looking at the same structure as either Shigo's 'compacted xylem', or somebody else's 'distorted'. Before you doubt the strength of that twisting wood grain, consider the relative effort of splitting firewood that is 'normal' vs. 'distorted'. You do split wood up nort, eh?


    "Shigo did like to emphasize the accessory buds at or near the terminal buds as producing stronger shoots. I think we can see that empirically.”

    Bingo! Yes we can! Thank you for confirming this.

    " A node is the position on a stem or trunk that was occupied by the terminal bud…Pruning cuts should be made at (terminal) nodes, or at crotches".

    “ But any traditional anatomist would hold that nodes are determined by the primary leaf axils."

    Then God Bless his non-traditional, empirical soul, RIP. Dr. Shigo went beyond the abstract dogma and aimed to the practical. He said clearly, and I agree with you, Kevin, we see this empirically.


    There's no turning back now! Not everyone has assimilated this knowledge yet. It takes time to see clearly, when the water keeps getting muddied by corporate interests. But now's the time to revise their antiquated training materials above the dumbed-down level they try so hard to hold us all down to. But it's understandable; it costs money to revise manuals, after all.


    "...the prescriptive guides use these formal anatomical terms." What guides, that prescribe which practice? A New Tree Biology prescribes our practice a lot more than the International Association of Wood Anatomists. After all, they guide the use of wood as a commodity. For us, wood is part of a living organism, with growing value in situ. The qualities of bud traces, and the gorgeously reinforcing compacted xylem around them, are understood by wood-splitters and wood-turners alike.


    Shigo's differentiation between well-formed buds that are accessory (next to a terminal bud) and semicongealed meristematic gunk in axillary (next to any old leaf) locations was a brilliant contribution to practical arboriculture. I think he might be flipping cartwheels right now, if anyone sought to obscure that essential differentiation with the broad brush of vague and irrelevant terminology.


    (These terms also define the narrow paradigms in arborist training manuals. This might explain why Asplundh, and the logging interests in the USFS, and the traditional educators like Bartlett are fighting tooth and nail against any fundamental change in the pruning standard. This might also explain why the only 2 members on the revision committee with an active and working knowledge of these inconvenient truths of tree anatomy and physiology, and their implications for tree care, were expelled from participation on the committee.)


    Shigo described nodal pruning well enough in A New Tree Biology for us to follow. After 28 years of transforming the industry, bit by bit, his accomplishment could only be overturned by a bucketload of data. Kevin, is there anything in the literature that supports a denial of the importance of terminal nodes? Appealing to authority by pointing to guides for the forest products industry does not inform arboriculture. Shigo’s work did.[​IMG]


    After the term 'nodal sprouting' in the attached was questioned, it might have been more inconvenient to vested interests if this chat had 20,000 peers to potentially review it---instead of what, 2 readers here who made it through all this?

    But better late than never!
     

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  8. KTSmith

    KTSmith Well-Known Member

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    Thanks Guy for your thoughtful post. Yes, it's often the defects that provide the most interesting and beautiful figure in wood. A New Tree Biology is a great resource, I refer to it a lot!
    Thanks also to TomD, TH, and JeffGu for participating thus far.
    My interest here is the original posted query, How do you recognize a node on a stem or branch? Or perhaps the thread has adequately covered that ground!
     
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  9. DSMc

    DSMc Well-Known Member

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    Unless there are obvious remnants of the terminal bud scale scar l don't waste my time looking as I have not noticed even the slightest difference that doing so effects regrowth or decay. When a heading cut is required in order to save an asset, I know that distorted and aggressive growth will follow. The presence of interior protection zones will either be there or they won't. Missing a potential node by a few inches will have little effect nor negate the need for a revisit in the future.
     
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  10. guymayor

    guymayor Well-Known Member

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    A node is recognizable by bulges and wrinkles at locations that indicate obvious remnants where a terminal bud was set. A decrease in taper is a very obvious sign.
    Take up a hand lens with you, and you might see the buds.

    Pic 1 shows a beech branch reduced to buds, compliant with A300 Part 1 (2008) at a visible node after an ice storm. (or it was 'headed back', if you prefer using Asplundh's term)
    2 accessory buds released, and grew toward the sunlight. 10 years later, I (unintentionally) hung 200# on one of these as I ascended. The sprouts had aggressively formed buttresses, thank goodness, or I'd've broken my butt after that sprout broke. Dave, what is 'distorted' about that sprout, now a branch, soon perhaps a leader?

    Pic 2 shows sprouts that formed at the base of a branch that declined, in the same tree that Detectable Decline described. Dang squirrels find the resources in that tissue sweet and tasty.

    Describing what Shigo and arborists call compacted xylem as a 'defect', and describing vigorous regrowth as 'distorted', seems to be coming from a forester's, not an arborist's perspective.
    Maybe those negative terms and viewpoints could be reconsidered, in the light of the tree's inclination to survive.
     

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  11. Redtree

    Redtree Active Member

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    I see some amazing discussion here. As a guy who makes 100-200 cuts a day I would say I make most of them at nodes defined by Shigo. But I don't agree with always making a cut at a crotch. We are very crotch oriented and not bud oriented enough. This may be wrong, but can a node be created? If not, a stem can be created at a point that seems internodal. And is internodal if we cut at a latent bud. So I'm also seeing the best cut as nodal, second best as adventitous, and third as latent. But all are an option in times of storm or heavy retrenchment? I'm seeing here that an adventitious bud is not a node. But is a node or a shoot created when we cut to an adventitious bud?. In reduction pruning we need to utilize this cut at least some of the time. Seldom but sometimes, a cut at a latent bud or better yet an adventitious bud. It may even be temporary but the option is there. And it might be planned temporary and then stay upon reinspection. If we come back in a few years and then cut at the crotch below, the cut to stem ratio will likely be better and have more of a branch collar. Thats the major point. Time is on our side and I think we don't utilize it enough due to TEMPORARILY poor aestheticS. Thanks KTSmith and Guy for opening my eyes on this terminology
    Correct me if I'm wrong but an adventitious bud is not at a node even though it is a potential shoot?


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    Last edited: Mar 12, 2015
  12. KTSmith

    KTSmith Well-Known Member

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    At the risk of sounding too pedantic and professorial...darn, too late for that! In our context here, "adventitious" is defined as arising in an unusual anatomical position rather than according to the regular pattern of growth. A classical botanist would term any sprout or branch not at a node determined by apical growth as adventitious. If the adventitious bud broke dormancy and made a woody shoot that after fifty years had a good strong attachment...it would still be adventitious and not at a node. I'm not trying to make any rules here. I've been wrong plenty of times, but the classic formal texts are readily available. Guy has shown us some good pointers for strong attachments which are critical for the practitioner.
     
  13. guymayor

    guymayor Well-Known Member

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    " And is it internodal if we cut at a latent bud."

    Nonononono. Latent aka dormant buds are at a node where the terminal bud was set, which is Shigo's definition, written for arborists.

    A shoot is often created when we cut to an adventitious (newly formed) bud, but that shoot is not as well attached as a shoot from a dormant (pre-formed) bud.
    But yes you are right: It may be temporary but the option is there. And it might be planned temporary and then stay upon reinspection.

    "Correct me if I'm wrong but an adventitious bud is not at a node even though it is a potential shoot?" Yes that's exactly right, for arborists, according to Shigo's definition.

    Whether or not that agrees with the botanical texts or the forester's terminology is a moot point, because we are not in college, or growing trees for timber.
     
    Last edited: Mar 12, 2015
  14. treehumper

    treehumper Well-Known Member

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    Once again, a big thanks for the discussion. The challenge in my estimation is being able to evaluate the branch to identify these various points, and make the resultant cut in a productive manner. Remember we still have many who hold fast to the mantra, "Don't think! Cut!" Can this be translated to some more fundamental guidelines for the average climber?
     
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  15. KTSmith

    KTSmith Well-Known Member

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    TH is right about the challenge, that was the reason for my question, how do we recognize nodes? We've got some good help on that, primarily from Guy. I think the emphasis on laterals might be to meet that need for guidelines. But now I am out of my depth!
     
  16. treehumper

    treehumper Well-Known Member

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    So, lets summarize what has been said and, "explain it to me like I'm a four-year-old."
     
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  17. KTSmith

    KTSmith Well-Known Member

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    Guy, I'm comfortable with different folks or traditions defining words in their own way to meet their needs! That is what language is for! We just need to be aware of those differences, particularly for folks that might be tempted to read outside of their specialty! That goes for "average climbers" and me alike. Shigo published his own dictionary to allow for his (and perhaps arboriculture's) specialized use of terms. So as long as one stays in that tradition, you should be all set!
    That's right, that's why I asked the question in the first place!
    I'm probably not the best equipped to handle TH's question. I've never properly climbed...although I have fallen out of a tree or two as an adult!
     
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  18. Redtree

    Redtree Active Member

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    I like both TH ideas. What's the simple way to say this stuff? I don't know because I still need to read more and try again, maybe in a year at the rate I learn and read. But I'm learning here.
    I like the point about the 'don't think just cut it'. Or 'if you had to think about it, cut it'. This drives me nuts as a rule to follow. If you have to think about it there's often a reason. So maybe reduce to a bud instead. Especially in storm damage. You may reduce two broken branches to the same crotch. Which is no longer a crotch if you cut the only two branches at that node. But it is still a node. Since storm damage repair I have cut both to a node, even if I didn't have to. Or, if I damage a stem meant to remain, I can cut it at a node (where the first cut was made). Then decide next time if I want to cut lower or not. If your not back for ten years, the problem has liked disappeared. The walnut I did yesterday had one damaged 5" branch with decay 4' out and zero risk for people and minimal for the tree. If cut at the trunk, the resulting injury would cause damage but likely not overly invasive. Leaving the branch, the decay would likely remain compartmentalized (as it likely put out the energy and work to do so once already) and likely not travel to the trunk. So I reduced to a crotched point out from the small area of decay. I had to think about it and not that cutting wasn't the better solution, but one fungus might have been traded off for another. And main stem exposure is worse than branch exposure.
    So I hesitate to admit that situation. But look at the other two extremes. If the limb was 2" at the trunk, id not think, I'd cut. If the limb was 12 inches, I'd think, and reduce, and cable if necessary. Possibly put the client at warning that if the decay gets worse the tree might need retrentchment, or even removal. Not removal soon but every urban tree will require removal at some point. The point is that the threshold for cutting at the trunk is often overstepped. I've done it, oops, but with good intentions. Can't get every cut on every tree right.
    Like a rubbing stem or poor spacing. If the removal of the rubbing, or 'correction' of the spacing results in a 12 inch stem cut I think we'd all agree not to cut, but to reduce. In the case of rubbing, reduction and or bracing is an option. On the other hand if the spacing or rubbing can be corrected with 1.5" cuts, I think we'd all agree, cut it.
    These thresholds are very important and deserve experiment. Maybe they already have been tested to some degree.
    These thresholds are also ranging largely between species. These thresholds change again when vitality is affected. Like in the planter pots of the city.
    I recently had a boulevard job and was frustrated with this. I ended up limiting the upper diameter limit to as little as 1". A few Norways in a developing part of the boulevard received no green cut over 3/4 inch. The idea was almost to just touch them enough to invigorate. They look good two years later. Two inch, green cuts on 10 inch, stressed Norways was too much. Or was it? I think there abilities to compartmentalize was poor and a few trees even proved that. Damaging the bark slightly, might not be good, cutting the branch off to remove the damage, might be worse.
    I just realized that I forgot again, that the walnut case (if decay progresses in a 12" limb)is missing the most important part of the solution. If retrenchment is suggested as the decay has progressed, then the tree is labelled like a temporary branch. The metaphorical equal to the remaining branch is the replacement tree. SO PLANT A TREE UNDERNEATH, OR HIGLY RECOMMEND IT AS SOON AS A TREE IS LABELLED AS TEMPORARY. Better than 'temporary' is 'short term', everything is temporary. Damn terminology issues again, ha.
    KTSmith, sorry for the derail, back to buds and nodes.
    [​IMG]
    Don't know if this is helpful. So this is a shoot from a latent bud, forced by the reduction cut above. Basswood. I left it on, but may have reduced it. It might even help support the compartmentalization of the cut above? And could facilitate future reduction, as cutting the one I'm around would have two stems to succeed. I think it's a two year old shoot. Is this really much stronger than an adventitious shoot? Thinking back I'd say yes, but maybe not always?



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  19. DSMc

    DSMc Well-Known Member

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    Hahaha!!! No forestry background on my end Guy, I just call 'em like I see 'em. I suppose those terms could be viewed as negative if that's how you look at things but they were used as merely a description of the typical growth one can expect to see from a heading cut that is large enough to not have easily visible nodal indicators.

    If the tree needs more interior growth, I will happily take whatever it will give me. I would not discard its efforts based on the origin of that growth.
     
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  20. Evan Sussman

    Evan Sussman Active Member

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    Before reading this discussion that is similar to what my response would have been. Mostly because I would have called used latent bud, and adventitious bud/shoot as defining two stages of a buds growth. Though as I recollect my thoughts I am aware of buds that are not apparently visible (dormant or latent), but do sprout adventitious shoots after certain pruning cuts, or damage to the branch from other factors.

    I appreciate this discussion, and have found it to be thought provoking.
     
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