Determining the correct pot size

[Krone]

Any tips and trick how to determine the optimal pot size ( width and deepth ) for the tree that will be potted from nursery container ( plastic container, styrofoam container, wooden box ) to a proper bonsai pot for a first time?
Considering that you don't have any data regarding the size of the root ball.

 

[Housguy]

From what I learned, the most important factor is the tree and pot need to be in scale. Obviously there are more factors as well, but that is the first one I look at before I go through the other factors.

 

[PiñonJ]

From Naka’s Bonsai Techniques, a good starting point is: height of pot about equal to the trunk thickness at its base; width of pot just over 2/3 the height of the tree. From there, you can play with the proportions, choosing a taller, narrower pot, or a shorter, wider pot.

 

[penumbra]

There are formulas, as that stated above, but they are never an excuse for taking off too many roots to get it into a pot that is mathematically sanctioned.
Roots first.

 

[Dav4]

Plan on having multiple pots available at the time of re-pot, and use the one that fits the existing roots the best. The first bonsai pot is usually over sized and considered more of a training pot. At each subsequent re-pot, it will either go back into the training pot or into an appropriate bonsai pot for the finished tree.

 

[Krone]

Thanks for all the answers, i am aware of the formula, but at this point my main concern is the root size.

 

[Tycoss]

How much you can reduce the root ball at a time has a lot to do with the species and health of the tree. I would reduce an olive a lot faster than I would reduce a pine.

 

[Krone]

Spruce, Cornus Mas and Prunus Mahaleb. All of them all ready for repot in next spring.

 

[Shibui]

Ditch the formula. It would be really difficult to keep a 1cm thick tree alive in a 1cm deep pot.
Just look for balance. If the tree looks top heavy the pot is too small. If you see the pot before you see the tree the pot is too big.

Different styles will look better in different sized pots. Cascade and semi cascade trees usually have a deeper than normal pot.
I've moved toward using slightly deeper pots than recommended because trees do far better in our hot, dry summers when there's a bit of room for roots and water.
Better for beginners to slightly over pot because that will give a little leeway while getting to grips with watering well. Larger pots also give more growth to help develop the branches and ramification if the trees need a little more.

 

[sorce]

don't have any data regarding the size of the root ball.

You can get some data!
Sometimes you can't see anything, sometimes a lift and look can provide all the information you'll need.

A diggy down from the top. Gather Data!

A Proper Air-Pruning Basket is best for a transitional stage, since you stand to get 3 times the feeders in the same season, rather than relying on a "safe time" to Repot and trim roots again.

I would Repot the spruce in a couple months, specifically, the first full moon after the Solstice.

Sorce