Late Summer Repotting experiment

As an experiment to test the viability of repotting in the summer, when leaves aren’t growing, and roots are, I repotted a Japanese Black Pine, and a Japanese Maple. The pine had been in that pot for a few years, and was building a good head of steam. It did not need to be repotted this year, much less in the summer. The Japanese Maple had been repotted this spring, aggressively root-pruned, and I was surprised how little the roots had grown when I unpotted it.

Just for an added degree of difficulty, here is the almanac of weather for the next couple months following the repotting, done on 8/11/19. Nearly every day was over 90 degrees, all the way until 10/5/19; 55 days over 90, 7 days in the 80s, and even a couple days over 100.

One month later, 9/15/19:

Two months later, 10/6/19:

It’s looking pale, but the buds are still doing ok. Here is a comparison of this pine next to another JBP:

4 months later, December 22…winter hue, or trouble? We have had several nights down in the mid-20s f, and none of the pines received protection.

Mid-March 2020. I’m reasonably confident the tree will live. Buds are swelling, but the color is pale:

Compared to another JBP from the same batch of seeds:

Late May, 2020. The dominant candle has failed, and a few other candles are opening.

Compared to the JBP from the same batch of seeds, which was dug from the ground this spring, and essentially bare-rooted. It is clear to me that March is a safer and healthier time to repot JBP:

Likewise, a Japanese Maple which also didn’t need to be repotted, and was, in fact repotted earlier in the spring of 2019:

Root pruned:

Wired in:

Watered in, 8/11/19:








10/27, new growth is promising:

December 1, After leaf-fall:

In Mid-March 2020, after spending all winter on the bench with other J Maples, I was a bit surprised to find this tree was dead…



Late May, 2020. A few shoots have emerged from the trunk. The top half of the trunk is dead, so I lost 2 sections of trunk which had taper and movement.

Conclusion: I will not be doing August repotting again.

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