Shallow pots for early nebari development?

[Kahless]

Hi. I am going to be taking some young seedlings out of my grow bed and putting them in pots in the spring. My plan is too focus more on getting better bonsai characteristics and less on growth for a couple years, and then put them in the ground to thicken up. My question is: Is there any benefit to putting these little trees in a more shallow container to train the roots to grow horizontally instead of down? Would it help with a more flaring root base? I have these little shallow tupperware containers (6" wide, 2"deep) with holes drilled in the bottom that I was thinking of using for the smallest ones. I know deeper pots would promote more growth, but I don't want any more trees that I spend years growing out only to find the nebari is bad. Or maybe this is something that you focus on a little later in development. I want to set these up for success as early as possible. Thank you !

 

[Wires_Guy_wires]

Shallow containers help, but you'd need to sort the roots as well. Otherwise one root might escape and grow feeders on its end, leaving the rest underdeveloped.
The coarser the soil particles are, the harder it is to produce fine roots all around.

 

[dbonsaiw]

I think there are two considerations at play - (i) what is the correct size of the pot; and (ii) how to get the optimal nebari. With respect to the first issue, the pot should correspond to the root system - small root system, small pot. If the pot is too big, you risk having the soil stay too wet and creating an anaerobic environment. Too small and the roots don't have room to grow. On a seedling, I'd use a fairly small pot.

On to the second issue. When you repot, trim off the tap root (if it has one) and any downward growing roots, leaving the radial roots only. Then, on the subsequent repot, you will again trim off downward growing roots and prune back the radial roots. This should be enough to develop good nebari over time. Alternatively, you can perform the operations I mentioned and plant the tree on something flat, like a piece of wood. This will prevent the roots from growing downwards, ensuring radial roots. On subsequent repots, you can trim the roots back to the size of the wood. If you want to be fancy, you can go the Ebihara way and guide the roots that are on the board so that they grow in the desired directions and also prune themselves when they get too big.

Don't forget to take advantage of the seedlings while they are flexible to wire some movement into the trunks, especially lower down. Alternatively, plant them on an angle so you'll have movement when you eventually prune it back.

 

[Shibui]

I get best results from root pruning.
Planting in shallow container or on a piece of wood does not preclude having some roots trapped under the surface roots and growing strong. Those roots push the others up and spoil the nebari. Best trunk flare is when there's only a single layer of lateral roots feeding into the trunk.
Don't be frightened of root pruning. Don't be lazy. Learn to root prune effectively for better results.

 

[Tele]

I have the same ideas on developing my trees.

I´ll be doing something like this: