Japanese Black Pines Root Pruning?

I have these JBP and I sprouted them last year and they need a lot more growing. But I am wondering, at some they'll need to be root pruned, correct? I've done some searching and found nothing definitive in this regard. If root pruned, when do you do it? I get it with deciduous trees, conifers, it escapes me.

Not in the dead of summer …. I’ll leave this one for other professionals here but you should be able to find a LOT of information on this exact topic online, YouTube, here on bonsai nut. Young JBP are easier to work on. In your next round of seeds you plant, you should try the “root cutting” method that promotes radial root growth and eliminates the tap root. Also lots of information and examples online form that. Goodluck.

And here is one from one of our very own members. @Darth Masiah

JohnFranklin - Zone 7b said:

I have these JBP and I sprouted them last year and they need a lot more growing. But I am wondering, at some they'll need to be root pruned, correct? I've done some searching and found nothing definitive in this regard. If root pruned, when do you do it? I get it with deciduous trees, conifers, it escapes me.

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There is lots of great information in this thread below as well. But rule of thumb is in spring once they're actively pushing buds, basically when all your deciduous trees have been done

eugenev2 said:

There is lots of great information in this thread below as well. But rule of thumb is in spring once they're actively pushing buds, basically when all your deciduous trees have been done

The 2018 Six Year Japanese Black Pine Contest

This forum will be for contest participants to track and report on their progress.

www.bonsainut.com

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Thanks for all of the information. This very helpful!

Those look very weak, if they were mine I wouldn't touch the roots until they were MUCH stronger. The pots they are in are plenty big for now, in my opinion.

you've missed the only window of opportunity for seedling cuttings, so I'd just try and focus on the health of the tree. don't repot. these pots look a little big for seedlings, so make sure the pot is getting a little lighter in-between waterings so the roots don't stay too wet.

Some growers repot before deciduous and do well. Others repot pines after deciduous and still do well. I can repot young seedlings almost any time of year down here and still get close to 100% success. I take all that to mean that pines are not particularly fussy about timing and the younger they are the less critical timing is.

Initial root prune on seedling JBP here is quite severe. I take the opportunity to remove any down roots and shorten whatever laterals are left. That stimulates more root ramification leading to much better nebari in future. Some people will be too frightened to root prune pines that hard and that's Ok with me. Just do what you think is good until you are comfortable they can survive root pruning at your place under your conditions.

Thanks All!