How To Thicken Bonsai Tree Base/Trunk

[Deleted member 47471]

I found Anderson Flats containers and can purchase them in a pack of 6. This is perfect because planting in ground is not an available option, and nothing else I’ve found thus far is sufficient.

So, the plan is to lay an initial level of soil in preparation for repotting, reduce tree soil levels to nebari, flare out the roots in array on the basin floor, then structurally tie down some roots to the floor for tree stability.

Example of JPN 3: 4”-5” in height

Example JPN 2: 9”-10” in height

Similar to JPN 1, idea is to tie down a few structural roots to stabilize tree and allow lateral root growth and building up base and trunk.

Questions:

a. How high, then, should I build up the total soil level? (if these are appropriate bin sizes) How much is too much for shallower but wider space?

b. Since the trees are smaller in size, should I altogether not use such wide growing bins?

c. Rather, should I reduce the size within the bin to accommodate the smaller trees so that the soil doesn’t span the entire width and floor of the bin?

I have trees larger in size that will surely thicken in these bins. Advice and input welcomed!

 

[Paradox]

If the trees are smaller, you can start with a smaller grow out pot and increase the size as the tree grows. Anderson flats are great for training and grow out but a ginormous pot for a small tree isn't needed. Go with something a couple of inches bigger on each side of the root mass. Let the tree grow into that the step it up.

I would try to keep it wide and shallow rather than deep to promote horizontal root growth.

Put at least an inch of soil on the bottom of the pot for a small tree, 2 inches for a larger tree and put enough on top to just bury the roots after you secure the tree to the pot.

 

[Deleted member 47471]

Understood. I will use the AF’s for the larger trees and acquire the appropriate sized containers for the smaller trees, and make necessary alterations per what you recommend. I appreciate the advice!

 

[Shibui]

Many trees produce new roots from the trunk when it is buried. Trident maples are notorious for it. Junipers do it too so if you tie the roots to the base of these trays and then add 4 or 5" of soil you'll end up with new roots along those 4 or 5" of buried trunk. High roots swell the trunk quicker than branches so when you eventually lift the tree and chop off the extra roots you'll almost certainly have inverse taper in that section.
Pines don't do this to any great extent so burying trunks may be OK however mature bark doesn't develop well on buried trunk.

If you don't fill the tray you will miss out on potential root growth and therefore trunk thickening. Shallower soil also tends to dry out and heat up quicker and reduces growth too.

I prefer to manage roots by manual root pruning. I get full control instead of just hoping they will grow correct. After the first good root prune to remove down growing roots the trees seem to put most effort into the laterals so I get exactly what you are aiming for without all the hassles of tying and managing shallow soil.
Others seem to put their faith in the Ebihara board method so the splayed roots are closer to the surface but still plenty of depth to grow down under the board.

 

[Coppersdad]

If the trees are smaller, you can start with a smaller grow out pot and increase the size as the tree grows. Anderson flats are great for training and grow out but a ginormous pot for a small tree isn't needed. Go with something a couple of inches bigger on each side of the root mass. Let the tree grow into that the step it up.

I would try to keep it wide and shallow rather than deep to promote horizontal root growth.

Put at least an inch of soil on the bottom of the pot for a small tree, 2 inches for a larger tree and put enough on top to just bury the roots after you secure the tree to the pot.

Totally agree. I'm not able to develop trees in the ground. I do put larger seedlings in 1 gal nursery pots and increase the size of the pot as needed until I'm unable to "lift the pot". At that point, it's as large as I care to work on. ( You know, there is something to be said for the wisdom of my friend who only has Mame and Shohin trees...)