Concave Cutter Advice

cedarcanvas

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I was doing some cleaning on my first tree, a savin juniper, with my new tools. I took off some branches (see below) and left behind some scars.

@Wires_Guy_wires left some super advice on my progression thread:

I see that you made some nice flush cuts with your new tools, I want to advise you to leave a bigger stub. Over time, those will heal nicer and look less man-made. If you're making concave cuts, make sure you make them deep enough so the trunk can roll some callus over it and engulf the cut site over time - not decades, but closer to 3-5 years. It takes some experimentation and a couple years of growing for a person to see how that actually turns out and what difference a couple millimeters make, but it's worth telling you about it now that you have a concave cutter.

I have a bunch of questions related to his post. This is one of the cuts I made:
AC92517A-7D68-4CA2-B81E-C7063D95E31A.jpeg
The photo makes it look bigger than it is and the lighting really highlights it. It is somewhere in the neighbourhood of a golf tee to pencil in size. I just used my branch cutter. I didn’t think it as prominent as it shows here but it’s raised some questions.

I am keen to minimize the appearance of as much man-made damage as possible. I understand what Wires_Guy meant by leaving stubs. I don’t think I’m ready/interested in the jin stuff yet...so I want to be minimizing scarring.

How big a branch should I be considering using the concave cutters on instead of just branch cutters?
How deep do I cut to maximize healing?
Can I go back now with my cutters a couple of days later and address this “knot” or is the damage done?

Cut paste/putty is a whole other debate I’ve explored on BonsaiNut. Suffice it to say, I don’t have any for now so will stick to tool work for the time being. I will also do a little experimenting, but would like to avoid damage. Thanks again Wires_Guy and anyone else who chimes in.
 

james

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Juniper almost never heal a wound like that. I didn't know this myself earlier, but have been told this, and didn't want to believe it. In my experience, I have not gotten juniper to heal such wounds. Rather, the branch to be removed is more often left longer and jin made. At some later time, several branch jin can be connected with shari. The cambium immediately above and below the wound tends to die back. It has nothing do with the specific tool used to remove the branch, rather it is the physiology of juniper.
 

Tieball

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I’d probably rough it up, gouge it up, it up to resemble the immediate surrounding area...the lumps and bark around your circle cut. Nature will start to improve it to a natural color or I'd use a very diluted black ink on it...very diluted....I'd just grey it up somewhat so it’s not staring at me. I'd disguise it.
 

Shibui

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I have had no trouble with junipers healing small cuts.
You can go back at any time and clean up any pruning marks. It is usual to leave a short stub for a few weeks or months then trim down to the trunk. That wait allows the tree to reroute sap that used to go to the branch so it now goes around the cut to other parts of the tree. Better sap flow past the cut will help in healing.

The best healing for the tree is when a small stub is left to preserve the branch 'collar' but that will leave a raised scar as the tree grows over the stub. For bonsai we do not do what is good for the tree but what is good for us. Start with the blades level with the trunk on the sides of the branch and cut. The curved blades should pull the cutter slightly into the trunk so the result is concave. The cutters are designed to make the concavity about right depth for it to heal flat with the trunk.

I don't know of any advice on which tools to use when. Just use the one that will do what you require.
Also note not to use cutters on too large branches. After I broke a couple of pairs I read the warning on Kaneshin website - branch diameter should be 1/2 - 1/3 of the blade width. Use a saw on branches thicker than 1/2 of your branch cutter blade!
 

Bonsai Nut

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Here's an example of jinning branches instead of cutting them flush (not my tree, just random image from the Internet). Go look at broken branches in nature. Very few will break off flush with the trunk. Junipers will heal branch scars, but only if you allow the trunk to thicken. If you keep the tree pruned so it doesn't get much larger, the scars will take forever to heal - if they heal at all. This is in contrast to scars on deciduous trees, which usually heal quickly.

DP94WV_U8AAQ4rP.jpg
 

james

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Here are some examples of my juniper after branches removed. Others may have different experiences. However, I would say (in general terms) mature juniper have twists, turns, Jin and shari. There are reasons for this. One of which is that branches removed flush with the trunk often don’t heal over completely.

43D5A5F6-8AE7-44C9-9462-8E67F39E03E2.jpeg

Branch removed 10+ years ago. Callous rolls around cut, but tends not to cover or close the wound.

6AEAF620-6D9D-466F-B637-270DF16F4B8D.jpeg

Similar results with another tree. Was never going to close, and I chose to cut in shari, which makes the hole or pit go away.

2393E8DA-CC9E-47D0-A906-7D056D59B875.jpeg

As I learned more about this, and watched what was happening with my trees over time, I simply take off branches long, take of bark and have a jin. Over time you can carve, lime sulfur as you like.

AB8F3D90-DE4F-4DD8-8F3F-53F9B68B468E.jpeg

More complex wound that never healed after apex taken off. Smaller branch used as the leader. Allowed to grow strong and then wound incorporated into a shari.

In summary, I found juniper wounds don’t heal well, they just don’t fill in. Rather the callous rolls around the wound leaving an oval, cat eye appearance. Not all is lost. The live vein of the cambium adjusts and simply moves alongside the wound. This habit can be used to build interesting jin and shari.

Take a look at mature juniper in nature, or bonsai. Most often these wounds don’t heal, and ultimately are incorporated into jin and shari.
 

Shibui

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I wonder whether this depends on the species or location or pruning methods?

I also use a lot of jin and shari on developing junipers. In my case almost all shimpaku.
I start out making fairly thin shari on smaller trunks with the aim if widening year by year to get the interesting look referred to above. I noticed that if I left it more than a year before widening the shari the initial cut was almost healed over and thinner areas had closed.
On another tree all the marks after approach grafting shimpaku onto another juniper trunk have now healed and it is actually difficult to pick the graft sites on that tree.
I will check and see if I have any examples of branch removal scars on my trees having healed.
 

Bonsai Nut

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I wonder whether this depends on the species or location or pruning methods?

It all depends on the vascular needs of the tree. If you remove a juniper branch, and then allow the tree above the scar to double in size/strength, the wound stands a good likelihood of healing completely. However if you remove a branch and then keep the foliage mass above the scar constrained, the scar may never heal - because the tree has no need for additional vascular development. You have to be careful because in some cases, if you prune a juniper and never allow it to strengthen, the margins of your pruning scars remain raw and new looking... for years. A sign of great age in junipers is not just the presence of deadwood, shari and jins. It is the continual growth and development of the veins of live growth - despite the tree living in adverse environmental conditions.
 
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cedarcanvas

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Okay, tons of amazing advice here, thank you everyone.

You can go back at any time and clean up any pruning marks. It is usual to leave a short stub for a few weeks or months then trim down to the trunk. That wait allows the tree to reroute sap that used to go to the branch so it now goes around the cut to other parts of the tree. Better sap flow past the cut will help in healing.

The best healing for the tree is when a small stub is left to preserve the branch 'collar' but that will leave a raised scar as the tree grows over the stub. For bonsai we do not do what is good for the tree but what is good for us. Start with the blades level with the trunk on the sides of the branch and cut. The curved blades should pull the cutter slightly into the trunk so the result is concave. The cutters are designed to make the concavity about right depth for it to heal flat with the trunk.

I don't know of any advice on which tools to use when. Just use the one that will do what you require.
Also note not to use cutters on too large branches. After I broke a couple of pairs I read the warning on Kaneshin website - branch diameter should be 1/2 - 1/3 of the blade width. Use a saw on branches thicker than 1/2 of your branch cutter blade!

This is super helpful and answers my questions! Next time I will leave the stub and clean it up later as recommended. I’ve been very mindful of diameter-to-tool ratios and you’ve given me a great rule of thumb here.

Here's an example of jinning branches instead of cutting them flush (not my tree, just random image from the Internet). Go look at broken branches in nature. Very few will break off flush with the trunk. Junipers will heal branch scars, but only if you allow the trunk to thicken. If you keep the tree pruned so it doesn't get much larger, the scars will take forever to heal - if they heal at all.

I have been looking at bagillions of threads and images of juniper bonsai and, unless they are top end specimens or naturally occurring trees, I very rarely see jin that appeals to me. I do agree the ‘natural’ trees have unclean breaks, no question...

No offence to anyone in particular, especially the people who took the time to respond here as I’ve seen some of your trees and I think they’re great...I just think it’s a personal taste thing. Perhaps it’s because a lot of the jin work on here is still in progress and so doesn’t have the true weathered natural feel, and appears to me to be a little contrived/forced...perhaps another element of bonsai that requires more patience than I’ve given.

I also feel that being a complete beginner this is outside of my skill level and perhaps less what I should be focused on at this stage in my progression (possibly at the expense of my trees’ progression). Likely something I will revisit down the line when I have a better grip on the basics of watering, feeding and other fundamentals.

Here are some examples of my juniper after branches removed. Others may have different experiences. However, I would say (in general terms) mature juniper have twists, turns, Jin and shari. There are reasons for this. One of which is that branches removed flush with the trunk often don’t heal over completely.

Thanks so much for taking the time to share and explain these images of your work @james. You have some awesome trees.

I must say, I’m more of a fan of the appearance of shari than jin. I think the “cavity” look in the first image above (post #6, photo #1) looks kinda neat. This gives me a great idea of what roughing up the bark and/or even creating shari can look like and seems like a decent way to address scars that I’m learning here are unlikely to heal otherwise.

I’ll be considering all the great advice given here and I’ll do my best to heed it in the future. I’m glad I have some time to address this and now have a good option to try to hide the scar and, when the time is right, learn to create a new feature on my tree. Stand by for shari questions.

Would love to hear more experience and/or advice!
 

Potawatomi13

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I was doing some cleaning on my first tree, a savin juniper, with my new tools. I took off some branches (see below) and left behind some scars.

@Wires_Guy_wires left some super advice on my progression thread:



I have a bunch of questions related to his post. This is one of the cuts I made:
View attachment 303193
The photo makes it look bigger than it is and the lighting really highlights it. It is somewhere in the neighbourhood of a golf tee to pencil in size. I just used my branch cutter. I didn’t think it as prominent as it shows here but it’s raised some questions.

I am keen to minimize the appearance of as much man-made damage as possible. I understand what Wires_Guy meant by leaving stubs. I don’t think I’m ready/interested in the jin stuff yet...so I want to be minimizing scarring.

How big a branch should I be considering using the concave cutters on instead of just branch cutters?
How deep do I cut to maximize healing?
Can I go back now with my cutters a couple of days later and address this “knot” or is the damage done?

Cut paste/putty is a whole other debate I’ve explored on BonsaiNut. Suffice it to say, I don’t have any for now so will stick to tool work for the time being. I will also do a little experimenting, but would like to avoid damage. Thanks again Wires_Guy and anyone else who chimes in.

Personally use on anything about 1/8" and over unless too big:D. Then use Pocket Boy saw. Cut paste applied immediately minimizes drying/die back around wound and may speed healing somewhat.
 
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