Repotting Strategy

As I go into repotting season, I think about how my plants grew the previous year and whether I want to change the soil mix I use for the upcoming growing season.

Last year, summer was mild which meant that many of my trees didn’t dry out between waterings. Among the pines, a few trees needed watering daily, but far more needed watering every two to three days, and some went about a week between waterings. I also saw more signs of root pathogens in the garden like pythium, an organism that thrives in mild conditions.

Although I don’t know what the weather will be this year, I want to hedge against another cool summer by using a mix that retains less moisture. I might have to water a lot if summer temps rise too high, but it’s easier to keep trees healthy by watering more frequently than by waiting for trees to dry out.

For conifers, I plan to limit akadama to 25-30% of the mix. For deciduous and broadleaf evergreen species, I don’t plan to use more than 50% akadama. I’ll also be using a much larger mix. The drainage layer will be coarse, and the upper layers will be slightly smaller.

Shohin pine mix (detail)

I’ve made similar adjustments in the past not just to accommodate changing weather patterns, but to encourage slower growth (by using wetter mixes) or faster growth (by using drier mixes) depending on my goals for the tree.

Of course, most of the repotting season has passed where I live and I’m only just getting started. Although it’s possible to repot bonsai any day of the year, it’s not possible to do the same amount of root work and expect similar results. I may hold off on a few repots or postpone them until spring (I’ll be repotting young chojubai then), for the most part, I’m repotting as usual and trying to work through everything as quickly as possible!

Kifu and shohin size black pines

If your repotting season still lies ahead of you, here are some repotting-related links to help.

• Repotting a trident maple (shows basic repotting steps)
• Repotting nursery stock – sekka hinoki
• Aligning containers with development goals
• What kind of soil should I use for my bonsai?

News & Updates

• We’ve been getting some great submissions for this year’s Pacific Bonsai Expo! If you’re thinking about submitting, learn more about the Call for Entries.
• There’s a unique opportunity to pick up some historical Northern California bonsai. Michael Uchida of Grove Way Bonsai Nursery is looking for a good home for a California juniper styled by Masahiko Kimura, a Western juniper styled by Shinji Suzuki, and a Monterey Pine started at Manzanar by Juzaburo Furuzawa. For more information, contact Michael at groveway.bonsai (at) gmail.com (serious inquiries only).

California juniper – 36″

Western juniper – 35″

Monterey Pine – 49″