Bonsai Tonight

An educational website about bonsai development

Bonsai Development Series #17: Thin foliage to preserve interior shoots

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Generating new shoots on Japanese black pines is easy. If a healthy tree is pruned, you can expect lots of new growth.

Over time, however, crowded shoots can prevent light from reaching the tree’s interior. When this happens, the interior shoots we rely on for future primary branches can die off.

The best way to avoid this is to periodically thin trees in development. Here’s what this looks like on a young pine.

Last year I cut back and decandled several neglected exposed root pines in an effort to generate new branches (see “Cutback and decandling” for details).

Exposed root pine

June 2018

After decandling in 2018

After cutback and decandling

The tree grew well over the following year and is now quite full.

Healthy pine

September 2019

Although pruning the tree will slow the thickening of the roots, it will allow me to preserve small interior shoots I can use as the future primary branches.

Most of this work involved removing young branches from crowded areas.

Crowded area

Crowded area with many small shoots

After thinning

After thinning

In more developed areas, I created rudimentary pad shapes.

Future pad

First branch on the right

Pad shape

After thinning

Here’s what the tree looked like when cutback was complete.

After cutback

Cutback complete

Although it’s too early in the tree’s development to focus on wiring every branch, it’s a great time to set curves in branches I plan to keep.

After wiring

After wiring – 20″ tall

I also exposed a few new roots by cutting away the top of the container.

Exposing roots

After reducing the container

Most of the roots are still small so I plan to keep them covered until they thicken.

Roots

View from the front

Although I typically wait until late October or November to work on pines, I don’t hesitate to prune trees in summer that haven’t been decandled. I’d definitely wait if I only had a few pines, but as I have more than I can count on two hands (or twenty), I find that getting started early is a great way to start the fall season.

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Comments

  1. Hi Jonas,

    I’m just starting out with pine seedlings and I’m learning a lot here, so let me say many thanks for that.
    With these exposed root pines, you have them very tall, can you describe why so tall? How long/tall do you envision the final root size to be, what proportion of the whole?

    • Hi Jeff! Over the years I’ve made exposed root pines in a number of configurations. As few of them have been tall, I’ve started making larger ones. Someday I’d love to see some that are 2′-3′ tall!

      I expect all of the roots in the tube to be exposed over time, and for the height to be similar. That said, I may bend the roots to come up with a new configuration based on what I find when the roots are exposed over the next 5 years of so.

      Thanks for writing!

  2. Hello Mr. Dupuich,
    help me with some information, please !
    If I have not decandled my Japanese black pine this year ( in June ) could I cut the sprouts of this year, this autumn ?
    The needles of one of my Japanese black pine have turned yellow. Which could be the cause of this ?
    I know it is not the best moment for repotting, but could I change the soil of one of them ?
    Loocking forward to your reply !
    With many thanks,
    Septimiu

    • Thanks Chris! Yes, I usually wait to pluck needles until the end of October or November. When I pluck early the odds are greater that the newer needles will tear the bark. If they come off easily I can pluck sooner. I also wait to give time for the new shoots on decandled pines to fully harden off.