Yesterday I bought 10 young shimpaku junipers in 3" pots. I intend to let these grow out for several years and then give them to my club for use in beginner design classes. I’m putting them into large (2’ x 4’) planter boxes for development, using tiles to induce horizontal root growth.
Right now the boxes contain garden soil. I’d welcome suggestions on soil amendments, fertilization and shaping to get them into the best possible condition. Should I treat them just like regular junipers in bonsai pots? Is it too early to wire? They are about 2-3" tall.
I’m a bit concerned about disease prevention but dislike using a lot of sprays. I will use insecticidal soap in a month or so. Anything else I should watch out for?
I’d like these to be a success.
You will get better development if they are put into grow bags in the ground with an organic nursery mix.
I was going to suggest moving them up in pot size for a year or two before the grow bag. I agree with the organic mix - I am using 50% bark, 20% steer manure blend, and 30% pumice based upon discussion of the book “Bonsai Heresy”. They are probably a bit small for wiring at this time - better once they are 8-10" (20-25cm) so there is something to actually wire unless you are looking to very small shohin.
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At 2-3" tall they have probably not colonized even a fraction of the current 3" pot. If that is the case, they will most likely do better in the current pots for a year as they develop more root mass since the small pot will warm up more than a large pot or the ground.