Shimpaku Juniper - Tips to maximise trunk growth

[tgooboon]

I am looking for tips for developing trunk of Shimpaku Juniper, I have mainly found tips on bending and twists, which is what I have been doing to date.

I have tried thining the grown and keeping the tips on a vigrously growing shimpaku juniper recently. It was fertilise heavily through spring and I will continue to fertilise heavily, keeping in full sun, and now in summer it seems to have vigorous growing tips. I thined out the green growth on branches, but keeping the growing tips. My thoughts are that the growth-tip should keep growing strongly, and with all of the green removed it will push the extra energy into tips, back budding and trunk base. See before and after photos.
Has anyone has any advice or if they have had success/fails with this method?

Shimpaku 2019-12-26 Vigorous Before-min.jpg

Before thining

Shimpaku 2019-12-26 After Thining-min.jpg

After Thining

I plan to plant these in ground in root control bags come spring, the branches will all be sacrafice branches.

I have another tree slightly larger with more more twists which is also in development, it is healthy but the tips are not vigorous like the first one, I am thinking of giving it the same treatment, but concerned it may not be vigourous enough.
Would I be better to wait for a couple of months or even another year before thining out like this?
or is Summer a good time to do this in development?

Shimpaku 1 2019-12-27 A-min.jpg

Shimpaku 1 2019-12-27 B-min.jpg

[shibui]

I'm not sure if it is the best way but I leave sacrifice branches to grow without thinning them out. I figure that the total amount of foliage on a branch is what feeds the branch, trunk and roots below. The only thinning I do is at the base of a sacrifice branch when the foliage is shading or competing with a part of the tree I want to keep in future.
It still take s quite a long time for these shimpaku to thicken. Even in the ground they need 5-7 years to get to 3cm thick.
I would just leave your second tree alone but feed and water well to try to stimulate some more growth.

I assume you already know that you will need to retain growth in the areas you intend to have as the final tree because junipers cannot be pruned back to bare wood.
Damaging the trunk may be a way to increase thickness faster as scar tissue is thicker than normal growth. Putting sharp bends in junipers causes localised thickening which I attribute to the damage healing under the bark. I have used cuts through the bark to help thicken other species but haven't tried it on junipers yet.
Curling young trunks into tight twists can help. As the trunk thickens the tightly twisted trunk fuses into a thick area. This must be done low on the trunk or the thick section can be layered so there is no inverse taper.
Shari can also increase the width of a trunk. The trunk continues to thicken as normal but can only grow where the live sections are so those areas grow faster depending how much bark has been removed. Note that it is a bad idea to make shari at the sides of the trunk because then it only thickens front and back which can't be seen and the width stays the same forever.

[kcpoole]

As shibui said, they are slow to thicken and aside from scarring as he mentioned the only other way to do it is to allow rampant growth on a sacrifice.
Keep the foliage down low where you want it in the final tree and wait

Ken

[PeachSlices]

leave some wire on and get a automatic shari

Simon

[shibui]

leave some wire on and get a automatic shari

automatic but also regular corkscrew - natural looking

[PeachSlices]

leave some wire on and get a automatic shari

automatic but also regular corkscrew - natural looking

if you do a bad job it could look natural???

Simon

[tgooboon]

I am going to avoid the trunk damage and shari for now. I will leave the second tree without thining out and see which one grows the most. I still have some growth close to the trunk on all branches to keep options open. Thanks for feedback

[Greg F]

Hi something else to try is to put it in the ground or a grow box for atleast a couple years and also feed heavily.

Greg

[shibui]

Shimpaku do not seem to respond as well as other species to ground growing. Mine grow just a bit for the first few years before finally starting to grow faster than the equivalent pot grown trees.
Take into account the drawbacks with ground growing - lack of control, eventual root reduction - and I'm not really sure it is worth while. Juniper are notoriously fickle when it comes to transplant and root reduction. I lost quite a few before finally working out how to do it well. Even now they take nearly a year to recover from transplant from the grow bed. Transplant from larger grow pots or boxes seems to be a bit easier.

[Greg F]

Neil how about squat juniper are the as slow as shimpaku in the ground? Ihave a couple of both in ground at the moment.
The biggest drawback has pruning difficulty.

Greg

[shibui]

I don't grow other junipers but I believe that squamata and procumbens both grow quicker than the Chinese junipers. That's why you see them so much as mallsai, and even as larger trees - quick growing so cheaper to produce.
Pruning difficulty is one of the factors I was alluding to when I mentioned lack of control. It is hard to assess which bits to prune and which to wire when lying on the ground between the rows and it is quite difficult to turn the tree around or try another angle. I've generally just put in some random bends and cut back anything that looks wrong while they are in the grow beds and that something worthwhile will result.

All this just explains why good bigger junipers are so hard to come by - lots of time and lots of mistakes along the way.

[tgooboon]

Have you tried root control bags? I heard about them on the telperion farms podcast. Work like an air pruning pot, it is nonwoven bag so the roots get caught and create back roots. They plant them in the ground, and it ke keeps 80% of the roots in the bag. They seem to be able to grow 5cm in 5 years.

I just planted a fig in one today. I am planning to plant some shimpaku in root control bags around late winter

[tgooboon]

Delete double post

[tgooboon]

These are the root control bags I am trialing. They are supposed to give accellerated growth, easy to transplant and good to develop a nebarri. They are nonwoven root control bags & they are supposed to prune roots similar to air pruning pots and you get the benefits of growing in ground accellerating the growth.

The roots get caught in the fabric and then send out another root from the trunkbase, creating a radial root pattern. Apparently 80% of the pots stay in the bag and there is no spiralling.

Root Control Bag 2019-12-30-min.jpg

I put some mix in the base of the bag

Root Control Bag Ply 2019-12-30-min.jpg

Then i put a plywood cutout to keep a flat base on the roots

Root Control Bag Shimpaku 2020-01-25-min.jpg

Then I plant the rooted cutting /plant above the ply and plant the whole bag in the ground

The first bags i got were only 150mm diameter and not very thick. Then I got some 250mm diameter and substancially thicker (300um thick), I have a Port Jackson fig here which I have repotted and planted in the ground

Root Control Bad PJF 2020-01-25-min.jpg

Now i just watch, prune and Grow.

[Ryceman3]

I’ll be interested to see how these go for you... never seen these in action, please keep updating with progress - I like the idea behind them.