AusBonsai

As the title suggests, I'm interested in what ways people have found success in thickening their Juniper trunks.
In my experience they are notoriously slow to thincken, despite having huge amounts foliage when in development stages.

I'm asking as I currently live in a rental with a very active Border Collie which together mean it's not really an option to 'field grow',
that being said I've tried a few "quick fix" ways and although they've worked well enough, they're prone to heavy scarring.
So I've tried purposely cutting the trunk up the tree and wiring the base and leaving it to just dig in and as stated work relatively well, but have potential for serious scarring if you aren't careful

What other teqniques are other people using?

You are absolutely correct about junipers being slow to thicken.

Ground growing has been the best here but even in the grow bed they take up to 3 years to start to grow. The next couple of years does see some better size though.
In pots the best option has been allowing sacrifice branches to grow. You can pick the place for sacrifice branches so they thicken up different sections of the trunk to give better taper. Yes, removing sacrifice branch will leave a scar but junipers are famed for dead wood so just leave a stump and convert to jin or incorporate any scars into shari on the trunk.
I have shimpaku here that have been slowly developing in pots with various sacrifice branches for 10-15 years and still not done to my satisfaction. I don't think there is any other quick fix.

I have found my procumbens have thickened up pretty quickly. I throw them in the largest pot I can find, feed regularly and forget for a few years.

2017 Last spring
Far from complete but you get a rough idea

shibui wrote:You are absolutely correct about junipers being slow to thicken.

Ground growing has been the best here but even in the grow bed they take up to 3 years to start to grow. The next couple of years does see some better size though.

Hi Shibui,

I’m curious about that delay to rapid growth: presumably it has something to do with roots settling in.
When you ground-grow Shimpaku, do you lift them regularly to do root work? Or does that obviate the benefit of putting them in a growing bed in the first place?

Andy

Hugh Grant talked about a method he has been using for a few years with young stock. He starts a shari before wiring, then over time maintains the shari which means the tree will only put on wood where the live vein exists. if it has plenty of foliage it will still put on plenty of wood, but only in a small area instead of a thin layer around the circumference. So you won't get a large circumference, but a thin and wide (if you get what I mean) trunk.

Interestingly I started some shari on older stock prior to hearing Hugh talk about it with the idea that it would create more interesting trunk shapes, but I haven't had a full growing season as yet. I have included a drawing to illustrate the idea. You can shape the live vein to lay wood where you want.

I’m curious about that delay to rapid growth: presumably it has something to do with roots settling in.
When you ground-grow Shimpaku, do you lift them regularly to do root work? Or does that obviate the benefit of putting them in a growing bed in the first place?

Not sure why shimpaku take so long to get started.
There seems to be no point lifting a tree that has not grown so I leave the shimpaku alone until the trunks have thickened which seems to be 3-5 years at my place. I have not tried dig and replant because, like you, I guess that each transplant will take a couple of years to recover again.
They do not seem to grow thick roots like maples so digging is no problem even after that long in the grow beds. I still seem to have plenty of feeder roots close to the trunk so transplant has not been a problem either.

One problem I did discover was straight branches. Natural growth of shimpaku is long, straight branches. In the ground this results in thicker straight trunks with little taper and little character - not ideal potential bonsai material in my opinion. Now I pre bend the lower trunks before planting out to thicken. I've tried bending in the ground but that is quite difficult so I've had much better results bending while the shoots are thinner, before planting out. Juts need to bend enough trunk for the size of tree you plan to grow.