This spring would be too soon for a repot. It’ll take at least a year to heal, if not two.
To dig into this a little further, I don’t have a ton of experience, but I’ll tell you about my recent trunk bending project. It was also on a Scots pine with about a 2" trunk.
I did the wedge cut and initial bend in the summer of 2018. I attempted to repot last spring (2019, a little more than 6 months later) and I ended up reopening the wedge cut (or, just as likely, it never closed). I completed the repot, re-wounded the callous and performed the bend again. Then I let it sit all last year. I am planning on letting it sit all this year too, or until the wire releases it’s tension on its own. So far, the wire holding the bend is still holding the bend.
Your situation might be heal quicker than mine (especially if you don’t re-open the wedge cut), but from what I can gather from all the streams, you’ll want to wait until after the wire holding the bend release it’s tension. Might be 1 year, might be more.
I would perform your bend right now before the tree starts moving resources in preparation of their spring elongation. You do this now to minimize bleeding or sap leakage, giving the tree time to compartmentalize the wound at the bend site. You should them fertilize aggressively the entire year, and most importantly, DO NOT CUT/PRUNE/REMOVE any growth above the bend this year. This unrestricted growth allows the tree to move all the resources through the remaining vascular tissue in the trunk or branch. The result is expansion of the tissue on the opposite side of the bend which is what is going to hold the bend you created.
Reportedly, the more radical the bend the faster it sets.
I would then the following year, do this: return to normal fertilizer schedule, make use of a sacrifice branch above the bend, resume refining the remaining branches. Do not touch your sacrifice branch as all this will be adding the vascular growth that will hold your bend.
You could then at this point probably perform a fall repotting after all the growth has completely hardened off. Obviously, depending on how you set up your bend you will probably have to be very gentle in regards to root work.
I would probably watch Ryan’s videos on how to handle issues with percolation and perform something similar to avoid repotting. You could instead add tape around your container, remove compacted surface soil and replace with fresh soil while using chops sticks to perforate through the compacted and otherwise untouched lower portion of the spoil column. This will allow water to pass into and through the container. A combination of all could work very well, in addition, to appropriate watering practices.
I believe that avoiding repotting would greatly benefit the tree in terms of gathering strength, healing the wound/setting the bend at a much more rapid pace. My pines, small/medium/large do not get repotted any more frequently than 5-6 years regardless of where they are in their stage of development.
If you get a lot of growth above your bend it may completely set in 3-4 years since the trunk is about 2 inches. Give your work the best chance for success you will not regret it!
Great reply thank you! That all makes a lot of sense, just one additional question. The tree was collected by a guy from the mountains in Northern Ireland three years ago and he placed into a straight mix of just coarse grit. It’s been in there with no work done on its roots for all of this time - I’m really keen to get it in a really good, proper mix of 1/3rd pumice, 1/3rd crushed lava, 1/3rd akadama. Should I do the repot next spring and leave the bend for another year? Or would I do best to do as you have said above?
Wow! That sucks - really disappointing for you. Hope your tree sets this year. How is the overall growth following the bend? Did it grow on ok with lots of new extensions?
It’s doing okay. It survived and grew last year. Not a lot of new shoots but lots of new growth on existing branch tips last year. But this year there are more buds set up so I’m hoping for a good rebound this year.
Fingers crossed for you then mate!
@AndyJ even though the tree is in coarse grit, I would probably leave the repot for the following year if the tree responds well after your initial bend. The coarse grit allowed the tree to recover after collection and will allow it to recover from a very large, aggressive bend. Pines are very dependent in their roots for their vigor. By not disturbing them you will get the best growth out of the tree. The grit makes it extremely difficult to over water as it does not retain water in the particle itself and will not compact or degrade.
I’m sure the microsphere in the container is well established, pines have symbiotic relationships with fungi and bacteria that aid in the uptake of nutrients and water. Another reason to avoid repotting at this time. Though the grit is probably inert I believe by not disturbing the entirety of the root system you will get the most out of the tree. No roots reduced will is another insult avoided to recover from.
Heavy fertilization will give the tree macro and micronutrients. You could use for instance organic fertilizer cakes monthly and organic liquid feed once a week or if diluted to 1/4 strength with each watering. The bonus of the grit in this case is that it has extremely low CEC and salt accumulation will likely not happen and can be flushed out with heavy watering without fertilization.
I like fox farm fertilizers or Alaska fertilizers, currently using fox farm grown big w/ microbrew and seaweed extract + monthly application of homemade fertilizer cakes (5-4-6) through growing season.
When I used Alaska products it was fish fertilizer with seaweed extract and fertilizer cakes. There is also a product called Neptune’s Harvest that is fish and seaweed concentrate, I used with great results as well.
I plan to switch back to Neptune’s with fert cakes and add microbrew soon as use all my current supplies. Mostly due to ease of application due to number of products being used.
Sorry for the rant, hope you find the information helpful.
IMO, the horticulture needs of the tree outweigh the “want” to bend the trunk. I think you would get far better results repottting into good soil this year, let it recover, push the new growth, increase the trees resources, and then do the trunk bend, next fall or winter. Bonsai is a marathon, not a sprint.
Good info Nathan - and good for thought. I like to see what other growers are doing
Absolutely agree Brian ref marathon not a sprint. I want this tree to grow strong and healthy and my natural inclination is to agree with you. I don’t know what the scientific / horticultural difference is for a tree in a lava / pumice / akadama mix as opposed to a tree in a well fertilised coarse grit mix? I must admit, I don’t understand things like optimal oxygen exchange and cation exchange, etc. I am using the LPA mix as that is what I believe is the best mix? So don’t know whether a repot or a trunk bend this year is best
APL is a great mix, I personally feel its a mix for refinement and not growing out or recovering from major pieces of work my example is this, Ryan performs major pieces of structural work on several streams. Majority of his conifers where he is doing this work are in grow boxes. Once recovered he will get them into bonsai pots when he begins refinement. Horticulture needs being considered, I would leave it in the the current planting box or pot. @Zencalc I agree with you that bonsai is a marathon, so why rush it into a pot and disturb the epicenter of vigor and strength?
@AndyJ if you PM and provide your email I will send you some studies for your personal objective review and exploitation.
@ndavila80 Brilliant - yeah I’d like that. I think I must be being an eejit - I can’t find how I send a PM?
@AndyJ hopefully those primers help you understand the dynamics of the soil and container. Large particles and tall soil column will give you a great balance of water and oxygen which will result in the growth you want to recover from a large bend.
Also check out this stream https://live.bonsaimirai.com/library/video/soils
He answers many of the questions directly and with a little extrapolation, why akadama mixes are for refinement.
I will be sending you a zip folder here shortly with some articles and other resources regarding various substrates.
Vindication today!!! During the stream Ryan answered your question about soil composition for maximum growth and healing, in tour case, setting that bend. Its about an hour and twenty minutes into the stream.
Unfortunately, I’m not a Premium member (I’ve only signed up for Mirai Live to watch the videos) - is there anyway I can watch the clip on Ryan’s Q&A?
It was on the live stream last night, should hopefully be added to the library on Friday.
@AndyJ I think there has been some good answers in here and some sound advise. I agree with everything @ndavila80 said about post bend care but I do this the advice @Zencalc gave to get the tree in to a good suitable soil prior to applying the bend it the best course of action.
Once your Irish pine is potted in to a good quality soil you wont be needing to re-pot for many years therefore allowing you plenty of undisturbed development. Always the the best course of action imo.
With all the respect in the world extended to @ndavila80 I see he lives in Texas? Well the climate in Texas is considerably different to to that of Carlisle. The recovery in your part of the world is quite different and by re-potting your pine I feel you will be vastly improving its recovery.
Please keep us in the loop as to what you choose to do.
@Dean_Kelly certainly true that the environmental differences would affect a tree’s growth patterns to some degree. However, location will not change container and soil (aggregate) dynamics. Akadama is used for its ability to scale down inside of a container I.E. it’s ability to refine trees.
Akadama has a modest CEC at best, and it is porous. This aids in that “water/oxygen balance” to create an idea environment to cultivate small feeder roots while allowing a tree to grow in a controlled manner. Welcome to bonsai and how it is accomplished. The remaining components in an Akadama mix have poor CEC and do not degrade. These are aggregates like pumice, lava, grit, haydite, and others. They contribute to soil structure, maintain the oxygen reservoirs in the container as the akadama “scales down” and retains more water for longer periods of time.
This would be the same independent of location.
Modern bonsai substrates inherently have very little nutrient content which necessitates fertilization at frequent, regular intervals. All this being said, I would try to accomplish the bend first and leave it in its current container and optimize its growth for the next few seasons. That way the bend can be set with strong growth and not set back several seasons due having to recover from a repotting. Bending a trunk is far less stressful to a tree than root work.
I certainly respect that people prioritize differently, and I in no way mean say that other approaches aren’t valid. They certainly are, have merit, and work well for many. My advice is simply what I feel is best to accomplish what the OP was inquiring about. Bonsai on and a great spring season to you all!