Surprised by Juniper structural work in late summer

Beginners
1

I’ve watched a few videos recently where Ryan has done major structural work on junipers in the late summer. I’m surprised. My Mirai Mobile App also has structural juniper work as a late summer option.

I understand it from the perspective of:

  • cleaning out 3rd year needles that are weakened in the interiors
  • increasing light penetration through the whole tree and for individual pads,
  • redistribute energy after spring growth
  • setting structure to take advantage of upcoming vascular growth

And only doing so if the tree is demonstrating spiky growth pushing outside of the silhouette, indicating strong roots and an overall foliar density that is ready to sustain and add. All good.

But its Summer! And Junipers derive strength from the foliage. Removing foliage even if its late summer and starts to cool down into August (not the case in Pacific NW or Cal, or pretty much anywhere these days) seems like bad timing. Is a tree energy positive if its in a dormant month and dealing with heat?

Unlike the winter, I would worry that eliminating large amounts of foliage through structural work in late summer would have two negative impacts:

  • Decreasing transpiration’s ability to cool the tree
  • Decreasing foliar efficacy right before it wants to drive vascular growth, decreasing vascular growth

Where is my horticultural knowledge wrong? What am I missing?

2

My understanding is that the bark is well adhered to the branches during late summer so it is safe to bend the branches without slipping the bark and killing the branch. Bark slip is fairly easy when the juniper is growing which rules out spring and fall. Winter would work, but the tree has to wait a few months before it can heal the damage due to bending. Late summer work sets it up to heal via fall vascular growth.

Your points about foliage removal are good, but I think the ability to safely bend the branches is more important.

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