Field grow Shimpaku

[Bakersbullion92]

So i have 4 Juniper Itoigawa that i purchased and are currently in 4” nursery pots. I want to get some good thickness and movement and put them into the ground for a few years to get bigger.probably 3 in the ground and one one a bigger pot. Is there any difference in this vs putting them in bigger pots? What soil type for good development for pots and good soil medium for the ground? And when it’s time to dig them up what would be best avenue for successful removal from the ground? Train root’s every spring kinda like the trident maple? Pre wire them before planting in the ground?
Thanks in advance

 

[Shibui]

Chinese juniper have been very slow to grow in the ground so probably allow more than a couple of years for good results.
Here, they typically grow very little the first summer, a little more the next season and finally take off in the 3rd and 4th summers in the ground.
Trees in pots seem to grow slow but steady from the start so will usually be ahead in growth rate until around 4 years. In addition, trees in pots can be worked - wiring, bending judicious pruning, etc to get far better trunk shape. In the ground you may get thickness (eventually) but you also usually get what the tree wants, not what you think is good. Chinese juniper tend to grow long, straight branches which is not a great basis for eventual bonsai. Some pruning or bending during the growth phase is really valuable IMHO.
Can't offer any opinions on soil types as I only have experience with the soil here and the one soil mix I use in pots. Other soils may give faster or better growth but I don't know what.

 

[Brian Van Fleet]

They will grow faster in the ground and require less care.

If you wire for movement, you’ll see that everything not wired will grow faster, so you’ll give up the first year for some movement, but likely worth it.

Don't dig up annually to work the roots, it’s not the same as tridents, and junipers need a few years unfettered to really start bulking up. Get the roots radially arranged once, and then just trench around the base 6” out all the way around every 3 years or so. I have dug up my crop once to prune for general shape and add a little Shari, and probably need to do it again next year.

Also, my itoigawa junipers in the ground grow very prostrate, and in the 7-8 years in the ground, they’ve managed to get about 18” high and 6‘ wide, so prepare for that. Trunks are approaching 4”.

 

[Bakersbullion92]

They will grow faster in the ground and require less care.

If you wire for movement, you’ll see that everything not wired will grow faster, so you’ll give up the first year for some movement, but likely worth it.

Don't dig up annually to work the roots, it’s not the same as tridents, and junipers need a few years unfettered to really start bulking up. Get the roots radially arranged once, and then just trench around the base 6” out all the way around every 3 years or so. I have dug up my crop once to prune for general shape and add a little Shari, and probably need to do it again next year.

Also, my itoigawa junipers in the ground grow very prostrate, and in the 7-8 years in the ground, they’ve managed to get about 18” high and 6‘ wide, so prepare for that. Trunks are approaching 4”.

Very good information. And what is your mix for the ground? I’m going to have to dig up good size depth and width because I have clay soil here. How are you fertilizing? How far apart is optimal for planting them?

 

[Bakersbullion92]

Chinese juniper have been very slow to grow in the ground so probably allow more than a couple of years for good results.
Here, they typically grow very little the first summer, a little more the next season and finally take off in the 3rd and 4th summers in the ground.
Trees in pots seem to grow slow but steady from the start so will usually be ahead in growth rate until around 4 years. In addition, trees in pots can be worked - wiring, bending judicious pruning, etc to get far better trunk shape. In the ground you may get thickness (eventually) but you also usually get what the tree wants, not what you think is good. Chinese juniper tend to grow long, straight branches which is not a great basis for eventual bonsai. Some pruning or bending during the growth phase is really valuable IMHO.
Can't offer any opinions on soil types as I only have experience with the soil here and the one soil mix I use in pots. Other soils may give faster or better growth but I don't know what.

And for your potted ones , what is your mix for developing? What is going to be a good size pot?

 

[Shibui]

what is your mix for developing?

I use the same potting mix for all trees in the nursery - 70% superfine pine bark: 30% propagating sand, both 3-10mm size. The mix also has iron, lime, dolomite, fertiliser and some zeolite. It may not suit all growers in all places but it is what I have access to and does Ok here.

What is going to be a good size pot?

Pot size depends on pant size. Little plants in oversize pots often do not do well. Best practice is to up-pot as the tree increase in size and root mass. Moving a small plant from a 3" pot into a huge grow box is likely to cause problems with roots rather than increase growth rates.
I plant rooted cuttings into 11cm diameter pots for a year or 2 then up into 15cm pots then into 20cm orchid pots as the trees develop and fill the previous pot with roots. Strong growers sometimes skip the 15 cm pots and go straight to 20 cm pots.
I mostly aim to grow small - medium sized bonsai now so don't usually go above 20cm diameter.
Horses for courses so use whatever sized containers you think will give the growth you want.