Experiment with me: Anyone got a light?

Wires_Guy_wires

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I've been dealing with a lot of nursery stock in the past years. Junipers especially, when they get huge cut backs, tend to produce a bunch of juvenile foliage.
They do this to stop grazing and increase photosynthetic surface, to recover faster from any damage and to prevent further damage.
All good, that's the nature of the beast! But it's ugly.

I've experimented a little and set a branch on fire on purpose. It produced some jet flames from the escaping oils and gasses, so watch your fingers if you try this.
To much of my surprise, the following growth was not at all juvenile but rather a continuation of the adult scale foliage.
I tried it on more junipers, and it seems that the burning of shoot tips does not cause the plant to revert to juvenile needle foliage.
But my space is limited and so is my stock. I did not make any pictures because I did think it was just a lucky outcome. But it happened a couple more times, and again I didn't take pictures. Sorry for that.

So my question to you is: would you help me out in collecting more data, and sacrifice one of your extending shoots (one that you would normally prune) by lighting it on fire instead of pruning it with a scissor and then tell me what happened?
Again, watch out for the jet flames and please don't hurt yourself. Keep a bucket of water close by, you don't want the whole plant to catch fire. Wet it beforehand maybe; all you'd want is to boil the internals, that can be done when wet.
Of course, after the shoot tip has died, I snap it off, because burnt foliage is ugly too. But if this happens to stop reverting the foliage in your stock too, we might be looking at a fun pruning technique.

I'm finding mixed messages about junipers and their smoke, please don't inhale it.

Thanks for any reports!
 
Hm.. not sure I understand. If I prune extending shoots, I never get juvenile foliage. I need to be a lot more extreme. Do you have an illustration of what you are after?
 
procumbens and nana revert to needles more easily. Perhaps you are dealing more with shimpaku/ itoigawa/ blaws?
Hm.. not sure I understand. If I prune extending shoots, I never get juvenile foliage. I need to be a lot more extreme. Do you have an illustration of what you are after?
 
Juniperus procumbens is a juniper with needle foliage. Not with scale.


I am not aware of a juniperus nana. What species are you referring to?
I think he just means Procumbens Nana, nana just implying it's the dwarf variety (though I've never seen non-dwarf Procumbens). They will get scale foliage here in Southern California if you do not work them too aggressively.
 
sacrifice one of your extending shoots (one that you would normally prune) by lighting it on fire instead of pruning it with a scissor and then tell me what happened?
I just tried and they basically won't light, at least not the green.. I have some junipers with brown stems that don't pull off easy and and those parts did burn, only with the help of a candle. So I think it would be easier than trying to scissor this brown stuff out.
I am drying then under an umbrella because they need a break from sopping soil, will post photos in a couple of days.
 
Juniperus procumbens is a juniper with needle foliage. Not with scale.


I am not aware of a juniperus nana. What species are you referring to?
Yes, procumbens (and p.nana) are "needle" junipers, however only in their juvenile stage of growth. Once the foliage is allowed to mature, they will convert to scale growth.

That is what (if I understand correctly) @Wires_Guy_wires is proposing.
Torching the foliage may trigger a different response from the material than the trauma of cutting might.
And is looking for volunteers to join him in burning their trees (carefully) and record what happens.

The bane of working on needle junipers is the ease at which they revert to juvenile foliage. If you can find a way to shape the tree without it converting back so easily, then a new technique is born.
I'm here for it 🔥
 
Nana here in Europe rarely has scale foliage. I only recently saw one plant that does.
Media, pfitzer, sabina in my yard are very prone to push juvenile scale after a hard prune. But when lit on fire, it doesn't happen.

I will upload a picture later today to show the difference within a single trunk.
 
Yes, procumbens (and p.nana) are "needle" junipers, however only in their juvenile stage of growth. Once the foliage is allowed to mature, they will convert to scale growth.
Nana here in Europe rarely has scale foliage.
Thats what I was thinking. J procumbens is defined as having needle-type foliage, and does not typically mature into scale. The same for the compact variety 'nana'.

Media, pfitzer, sabina
:) I try to avoid these. I have one spanish sabina, so not the gardencentre version. It was unfortunately a bit pricey and has taken me 4 years to get to good health. No experimenting there.

I have 2 junipers of which I do not know what they are, but those are being grafted with ittoigawa. The latter also does not revert to needles as much. Guess I will not be able to help.
 
:) I try to avoid these. I have one spanish sabina, so not the gardencentre version. It was unfortunately a bit pricey and has taken me 4 years to get to good health. No experimenting there.
I have those too, remarkably they do good the first year and then collapse. My youngest recovered in the first year. The oldest is still so-so.
Pricey indeed.

I think the americans have different genetics in their nana, potentially mixed with horizontalis. In Germany some imported nana varieties are showing scale, but they originate from the US. The nana we have here does not show scale behavior whatsoever, not even after 30 years in the ground. I've looked around in literature and couldn't find any explanations other than my gut feeling which is that they're hybrids with something. From the size of the worms and the lack of a change in growth habit, my best guess is horizontalis. That however, is something for a different thread I guess.
 
I have those too, remarkably they do good the first year and then collapse. My youngest recovered in the first year. The oldest is still so-so.
Pricey indeed.

I think the americans have different genetics in their nana, potentially mixed with horizontalis. In Germany some imported nana varieties are showing scale, but they originate from the US. The nana we have here does not show scale behavior whatsoever, not even after 30 years in the ground. I've looked around in literature and couldn't find any explanations other than my gut feeling which is that they're hybrids with something. From the size of the worms and the lack of a change in growth habit, my best guess is horizontalis. That however, is something for a different thread I guess.
Could be. My procumbens nana in Los Angeles is about 40-50% scale foliage. I just recently gave it a large trim so we’ll see what the new foliage looks like.
 
Wild speculation, let's not run with it until there is any kind of proof to it.
Well, the fact that they have scale foliage whereas the original species has not and was never described as such, does mean something.
If we take general plant genetics, the phenotype is different enough to suggest there's a different genotype. For me, that's enough to run with. And I will until there's people willing to spend money to prove me wrong.

.. Which would mean they are not procumbens nana anymore ofc..
Naming of cultivars is kind of arbitrary, depending on where you are in the world, you could name a scopulorum a procumbens nana and nobody could stop you. Not all of these names are protected and latin nomenclature usually comes down to "if there isn't any active discussion in the scientific field, why bother to change it?". See the rigida vs. conferta discussion; nobody can really tell what the difference is other than the growth habit in some cases. Genetics have shown them to be different to a small extent, but is that enough to say they're entirely different genotypes? Interestingly, today I learned people are planning to group Denisovan hominids under the Homo sapiens instead of Homo denisova "because they look alike". Not very scientific, but that's biology for us.

Anyhow, back to the burning of foliage. Below an image of the part of the apex, circled in red where I burned it. It regrew only scale. I burned another tip to be sure, top left.
IMG20250708174500.jpg
Below an image of scissor pruned branches, just now reverting back to scale. Same trunk, just a couple centimeters down.
IMG20250708174520.jpg
 
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