Is repotting necessary for Conifer trees in development

jmmzpsu14

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So just a question out of curiosity I’ve skimmed several forums and couldn’t find the question exactly what I’m asking so I’m going to do that now. I’ve been reading a lot of articles on soil , back-budding along with watching several videos on repotting bonsai in development. Videos on bonsai in development seem to focus on candle pruning or bud selection on pines/conifers. It seems straight forward that deciduous in development really don’t need to be put in bonsai media or at least can be placed in a grow box with pumice or root promoting media. Collected pines/conifers develop good roots when placed in a grow box with substrate. But what about pines or conifers that are still in development from seed or nursery stock, does the tree really benefit from repotting and root pruning for inorganic substrate before it’s 75% complete in growth/development. You’d still obviously wire , prune and pinch/cut buds or shoots. But,does back budding and trunk growth differ between organic and inorganic soils. Which soil media would be a better catalyst for this to occur. It seems obvious that planting in ground and pruning back field grown trees yields large trunks , and controlling roots using a pond basket or tile can help as well. But how can this be done in a pot / does inorganic or organic really matter for growth stage/ which would be better.
 
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sorce

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does the tree really benefit from repotting and root pruning
Straight away, the only benefit is an aesthetic one for the roots, which is absolutely required for trees that have been grown in nursery pots, and seedlings to prevent them from getting that way.

Once you establish a good mass of roots that fits in a pot space, it becomes a horticultural benefit as well.

But cutting roots will always set you back, just depends by how much.

Sorce
 

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So just a question out of curiosity I’ve skimmed several forums and couldn’t find the question exactly what I’m asking so I’m going to do that now. I’ve been reading a lot of articles on soil , back-budding along with watching several videos on repotting bonsai in development. Videos on bonsai in development seem to focus on candle pruning or bud selection on pines/conifers. It seems straight forward that deciduous in development really don’t need to be put in bonsai media or at least can be placed in a grow box with pumice or root promoting media. Collected pines/conifers develop good roots when placed in a grow box with substrate. But what about pines or conifers that are still in development from seed or nursery stock, does the tree really benefit from repotting and root pruning for inorganic substrate before it’s 75% complete in growth/development. You’d still obviously wire , prune and pinch/cut buds or shoots. But,does back budding and trunk growth differ between organic and inorganic soils. Which soil media would be a better catalyst for this to occur. It seems obvious that planting in ground and pruning back field grown trees yields large trunks , and controlling roots using a pond basket or tile can help as well. But how can this be done in a pot / does inorganic or organic really matter for growth stage/ which would be better.
You are talking about trees in development. This includes developing the proper nebari and root ball for long term function in a Bonsai pot. Does not matter if the tree is deciduous or conifer, the time must be taken to develop all characteristics. If you focus on only one it will be at the expense of the others.
It can be done in the ground, in raised grow beds, in grow boxes, or in pots if suitable size is chosen. The substrate can vary if appropriate balance of air, water and nutrients is provided.

Your questions seem directed at finding the one best way, too many variables and possibilities to declare one best way! If you focus on only one it will be at the expense of ignoring the benefits of the others.

A method that I prefer is to combine the benefits of various practices.

1.focus early on developing basic structure of nebari and movement in the trunk as desired. ( pots, grow boxes)
2.switch to thickening trunk and developing options for sacrifice branches, sacrifice leaders. ( grow beds, grow boxes , in ground )
3.next, taper and primary branch development. ( grow beds, grow boxes )
4. Only work towards smaller containers after nebari, trunk, taper and primary branches are in place. ( maintenance pots )

Pick a method that works for your available budget and resources.
 

jmmzpsu14

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Thank you for the detailed response those sound like good options and something to think about as I have trees in different stages of development although they are in development as bonsai. But I’m thinking most will be in substrate suitable for each type/stage and the grow beds sounds like a good option to develop taper in a few I have. I’ll also be staying in same size pot or smaller for some that have the basic branch structure in place.
 

Leo in N E Illinois

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For pines, a pumice based mix is ideal. Even fairly early in development. Pines do not "like wet feet" in that fungal and bacterial difficulties arise if you use a water retaining mix like "potting soil" even with young seedlings. A free draining mix will allow better, finer root development. A mix that is at least 50% to 75% pumice & or a pumice & lava blend is great. The rest can be your media of choice; bark, akadama, turface, whatever. Even with seedlings this type of mix will give better root development. Repotting of pines should happen initially every 2 to 5 years on young in development pines, in order to work on the appearance of the nebari. Once the nebari is "set on the right course", interval between repotting can be stretched out. As long as the media drains freely, there is no immediate need to repot except to work on the development of the nebari. Middle and advanced stage pines can go 5 to 10 years or more between repotting

Each time you repot, you set the tree's growth back. But some of the set back is beneficial. You want to keep internodes short. You do not want rampant elongated growth for bonsai.

Pumice, lava & akadama blend is highly recommended for trees in advanced stages of development. On young trees, the expense of akadama limits its desirability for early development trees.

Only valid reasons to repot
- mix is no longer draining freely
- you need to correct root arrangement in the nebari
- you need to change the angle the trunk leaves the soil - style and design. This will require correcting root arrangement, so is included in above reason.
- you want to slow down the growth of the tree - done more often for deciduous trees to slow growth of maples and elms, etc. Less often used to slow growth of pines.
- you want to prepare for show the following year - change from "everyday pot" to show quality pot.

Otherwise, there is a tendency of most newer to bonsai to repot their trees too often.
 
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Japonicus

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Agreed with Frank and sorce's replies. In short, answer is yes it is necessary.
Think about transitioning from one soil type to another also.
I think most of us replace more organic with inorganic with each repotting on most of our trees
with a few exceptions of bare rooting all at once. So while you're addressing the root structure each time
you're also limiting the stress of relocating the mass in a different type soil. Don't miss an opportunity to remove more original soil.
There are several benefits to repotting during development, but we Westerners do tend to repot too often.
You have to find a balance. Like Frank said...for example I left a shinpaku in a nursery can, in bonsai soil
for 12 years. Trunk development suffered I think, because I spent more time on the foliage, and mostly pinching at that.
Root development suffered no doubt as well, limiting radial spread to the surface size of the container.
 

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