Confusion Over Fall Repotting-
I’ve noticed over the years a lot of puzzlement over the correct time to repot. Much of the confusion stems from placing too much weight on the exceptions to spring repotting. There’s a simple way of looking at it that might help decide when to repot.
Ron Weasley pulls up a mandrake
When we repot, the tree is essentially given the signal, ‘Hey, it’s spring, let’s grow!’ Not necessarily on top…a tree repotted in fall doesn’t often grow on top. But the roots are often as active as if it were spring, because the tree is trying to regrow what was cut off. Then winter comes. And if we’re in the north, blasts of freezing weather can obliterate that tender root system, and kill the tree.
In general, only repot in the springtime.
If you must repot in the fall, do it only if you have protection from freezing weather, such as a greenhouse.
Naturally, many exceptions exist. A few of them are:
- Some species, like azaleas, begin their extension cycle after flowering, so in some climates (not blazing hot, dry ones), repotting after flowering in late spring/early summer might be preferred.
- Spring in Lost Angeles is wintertime for most other places. LA doesn’t really have a winter, so bonsai are usually repotted in December/January.
- Trees with root problems might need repotting at any time of the year. This might be simply transferring to more open surrounding soil, even if no real root work is done, and even if the timing is not ideal.
- Yamadori collectors often find summertime and early fall to be good times, as the mountains can be hard to navigate in early spring weather, and then, a good secondary time to repot is after needle growth on pines has stopped.
- Plant nurseries sometimes repot at very interesting times of the year, like summer. But it’s best not to emulate them, as they have pinpointed when, and how much, and what kind of aftercare. Those professionals exist on the outsides of the bell curve, and they are there for a reason.
For most of us in bonsai, repotting in the springtime (whatever that is for you) will prevent a host of problems with reestablishment of the roots and growth of the tree.
Just keep in mind that repotting, translated, means ‘grow’ to a tree. And repot accordingly.
10 Comments
Good article Michael.
Thanks for the info. Makes it very clear.
Hi Michael,
I agree with spring repotting in its truest meaning especially if root work is involved but I’ve had much success with transplanting (slip potting to be exact) in late August, early September especially when we get a nice period of cooler wet weather as we often experience. Roots are very active which does provide root egress into the newer soil….maybe it’s our longer days up on the 50th lol.
Cheers Graham
There are a million exceptions to what I wrote, and you have found one of them. Slip potting may be done anytime of year. But a normal repot with root removal is best done, again for most things and most purposes, in the spring. In the Northwest here we have a lot of latitude for fall work, it’s very close to spring, but this blog has a global reach.. ; )
Hey Michael I am about to do a design install for a client. She has several bird nest spruce that I have to remove to plant the new ones. I would like to pot up some of them. I’m in St. Louis. Suggestions for winter care?
Jamie Brown Outdoor Creative Design and Landscape, LLC. 2579 Rock Hill Industrial Court Saint Louis, MO 63144 314-276-4732
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Just protect the trees from freezing weather and they should do fine- Even some low wattage heating mats could benefit root growth, and protect from cold, too.
Thanks for the info Michael. I have read that quince are an exception. Is that you experience regarding Japanese quince? I have a recently purchased nursery stock that I was planning on pruning and transplanting soon.
I’ve repotted them both in the spring and fall and they are fine with both. Many claim an advantage with fall repotting in that it gets ahead on the bacteria that causes root galls, but I sterilize for that so I don’t find time of year limiting. The trees themselves are strong and repotting in the spring is not going to affect flowering.
Your pronouncements read like regurgitated dogma. I dont know who you are or your gardening experience but in matters of horticulture legit citations should accompany prescribed recommendations
Yes, I understand the reservation. In bonsai we have few citations to offer, unfortunately. Although being an apprentice in Japan for years, as I was, does not imply that one has acquired the tradition (I knew many who hadn’t), it’s a place to begin. As for the seriousness of my own reservations about what is talked about in the bonsai community at large as being ‘true’ and ‘efficacious’ in the world of bonsai, I am writing a book about the subject and wrote a blog post about it: http://crataegus.com/2018/07/27/new-book-bonsai-heresy/