Boxwood Hard Prune in Summer

This Japanese boxwood was part of a hedge at my parent’s place. They were expanding their carport and asked if I wanted any of the plants for bonsai. I said yes. At the time, in 1994, the boxwood was about 40 years old, making it around 70 now.

Like many broadleaf evergreens, after the first flush of growth hardens off there’s a chance to cut boxwood back. Cutback is best done in summer for them to leaf out before fall. They like the heat. Try to time it a few weeks after hardening off, to give the plant enough time to restock its sugar supplies so it can regrow from cutback.

We did this a bit late for our neck of the woods, here in the Pacific Northwest, USA. If you have a lot of summer left it might still be possible for you. Or, keep in mind for next year.

Be sure your plant is strong, with good extensions. Also, boxwood respond best if fertilized well in the fall, and in the spring, to do as drastic a summer cut back as shown here. 

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Japanese boxwood in a training pot “spa” to ramp up vigor. The plant hasn’t been touched all year. 

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Carmen making the cuts…

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Cutback finished. Another example of this is our exercise with Satsuki azalea. For this to work well, cut back inside the ideal canopy size, and let the tree grow out to meet it. The look of this one does remind me of ficus and hibiscus defoliation techniques, in preparation for display. Old boxwood don’t have the energy of a ficus, though, and I don’t recommend this as an annual technique.

This was the boxwood 26 years ago, two years after removing it from a hedge. I wrote this article for International Bonsai the year I left for my apprenticeship in Japan.

August 2022 Bulletin Board

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6 Comments

  1. Ray says:

    Thanks Michael, great info.

  2. treetroll1 says:

    Does this apply to the kings vile box as it does to the “normal” variety!

  3. Todd D Morgan says:

    here in Santa Cruz, CA, my boxwoods never lose their leaves, just turn a little reddish paler. and I have never defoliated, boxwoods. didn’t know you could. haven’t really noticed any particular timing of new shoots “hardening off”. they just kind of green back up better.
    when should my first defoliating happen? In Summer? then again during the year, or just wait until the next summer?
    Or is defoliating just something to do to boxwoods up farther north, with real winters?
    thanks.

    • crataegus says:

      Hi Todd—- Correct, they won’t lose their leaves naturally. Old leaves will die off but the plant will always retain some green leaves. Defoliating is possible, on strong plants, and it essentially “resets” the spring, forcing the plant to regrow. Usually it will regrow with smaller leaves, more buds, and greater ramification. I would only do this once every 2-3 years. Right after growth (early summer in many areas).

  4. chasmosse says:

    When was the last fertilizing before defolation? When did you start up fertilizing after defoliation or have you not yet to keep the leaves smaller and internodes shorter? The difference in the leaf color before/after is fairly dramatic. Why? Great results. I did some small scale defoliation/partial defoliation combinations on a boxwood. Worked good. Your results are particulary good. Hope I can do that.

    • crataegus says:

      We were fertilizing this boxwood right up to defoliation. It was a late cut, but usually I would have stopped fertilizing a week or two in advance. We did fertilize soon after pruning. And again it was mainly that this was later than I’d usually do it. I think often that greenup is related to a better root/shoot balance achieved through pruning, and somewhat to fertilizing that we manage to optimize. Often this doesn’t seem to have a magic formula.

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