Frequency of repotting

[ConorDash]

Hey,

This started as a message to Bobby but sounded like a good discussion point. As I don’t tend to make any discussion topics, I thought I’d go for it (live dangerously!).

Reading through Harry Harrington’s first book, one of the bits of advice is to repot every 1 or 2 years.

Now, I’m not too fresh off the Bonsai boat. I’m comfortable and confident in knowing when my trees need repotting, so this isn’t a big “help wanted” topic. Just discussion.

I was thinking perhaps this timing is for later staged Bonsai, in proper pots? Not ones in development, larger pots.
Personally, I’d have said 2-3 years for a repot.
Bearing in mind this is all general advice and not taking in to account specific species, climate and age of the tree.

What are your thoughts?

 

[Dav4]

It really depends on what you're growing and how developed they are. For younger maples that need lot's of root work, I re-pot annually. For those same trees that are further along with roots fairly set, I may still re-pot annually (the roots CAN always get better) or every other year. For developing pines and junipers, every 2-3 years, and for mature trees maybe every 4-6 years.

 

[BackyardBonsai]

Ryan N has a YouTube video talking about this. Why and when.

 

[Gustavo Martins]

I believe that thinking about this in terms of years is kind of pointless. You repot if:
- Pot is too small for a tree which is becoming unhealthy as a result
- the potting soil looses percolation
- you need to work the roots for whatever reason
- aesthetics.

This could be 1 up to 20 years I suppose. It all depends on tree stage, soil used, size of pot, species of tree.

 

[Walter Pall]

I believe that thinking about this in terms of years is kind of pointless. You repot if:
- Pot is too small for a tree which is becoming unhealthy as a result
- the potting soil looses percolation
- you need to work the roots for whatever reason
- aesthetics.

This could be 1 up to 20 years I suppose. It all depends on tree stage, soil used, size of pot, species of tree.

exactly!
Repot only when necessary. Often it is not necessary for many years. Repotting and cutting roots is NOT good for the tree, it is like taking away half of your blood. That is NOT good for you!

 

[Stan Kengai]

In my experience, people tend to transplant too frequently and use pots that are too large. If you are using good soil components and properly sized pots with adequate drainage, you should be able to go at least 2 growing seasons between transplants for all but the tiniest of pots.

In the first growing season after repotting, plant's roots tend to grow out to the perimeter of the pot then circle around the walls of the pot. These roots are long and fat. The corresponding top growth tends to be long and fat. In subsequent growing seasons, you will see more root growth on the interior of the pot. This root growth is finer and more ramified, which obviously corresponds to finer and more ramified top growth.

How many times have you taken a plant out of a pot to find roots circling the sides and bottom with virtually no root growth in the interior? Transplanting too frequently is one of the causes of this phenomenon, along with poor watering habits, improperly sized pots, and poor or improperly sized soil.

 

[Leo in N E Illinois]

Gustavo and Walter Pall echo my sentiments exactly. Repot only when necessary.

Peter Tea that you should only repot for a purpose, or a reason. Not because of a mythical schedule. Gustavo's list is appropriate.

Peter did mention that sometimes exhibition ready maples are repotted the spring of the year to be displayed in order to deliberately slow growth for that year. Younger maples are sometimes repotted 2nd or 3rd year just to slow growth down growth.

If the potting mix is still draining well, and the tree is holding enough water to get along with your watering schedule, there is no reason to repot. (I can't water more than once a day, so I repot to a larger pot if a tree needs more than once a day watering).

 

[ConorDash]

I believe that thinking about this in terms of years is kind of pointless. You repot if:
- Pot is too small for a tree which is becoming unhealthy as a result
- the potting soil looses percolation
- you need to work the roots for whatever reason
- aesthetics.

This could be 1 up to 20 years I suppose. It all depends on tree stage, soil used, size of pot, species of tree.

exactly!
Repot only when necessary. Often it is not necessary for many years. Repotting and cutting roots is NOT good for the tree, it is like taking away half of your blood. That is NOT good for you!

Points both well made, thank you.
I’m not too naive to repot or water on a schedule, don’t think me too silly .

Just interested in the discussion, which has resulted in good info for all. Thank you both.

 

[dirk hoorelbeke]

Repot on demand, not on schedule. If you don't create better roots or help in an other way, you're not doing the right thing. A tree needs to be ready to stay longer in a pot. A healthy and firm center that can absorb and give water when needed. You need to repot and work the roots more often when that is not present.

 

[Zach Smith]

I think in terms of species and specimen. Some species are "super rooters," for example Crape myrtle. They grow roots so fast that they will literally run out of soil within a couple of years at most. So repotting to give fresh soil to support nutrient absorption is a must. And there is variation from specimen to specimen. You might have two maples side by side on the bench, one of them grows roots faster than the other for whatever reason. That one gets repotted sooner.

 

[Orion_metalhead]

Is it fair to say that you'll be repotting much more in the early life of the tree, just to get the roots structured properly? Once you've got the roots organized and in the direction you want them to be, you can re-pot less.

 

[Walter Pall]

Is it fair to say that you'll be repotting much more in the early life of the tree, just to get the roots structured properly? Once you've got the roots organized and in the direction you want them to be, you can re-pot less.

That's true. Collected old conifers I repot ONLY for artistic reasons to get them into the right pot in the right position. After that I leave them alone for ten years and more. Because it is not necessary to repot and would be silly because of risking the tree again.

PREREQUISITE is coarse , well draining substrate the does NOT decompose - like pumice or turface. Cheap unfired akadama is not good at all because it does decompose. Those who use unfired akadama should not listen to me. They would kill their trees not repotting them frequently.

Old collected broadleaved trees usually I do not repot for 5 to 7 years.

 

[SU2]

I was thinking perhaps this timing is for later staged Bonsai, in proper pots? Not ones in development, larger pots.
Personally, I’d have said 2-3 years for a repot.
Bearing in mind this is all general advice and not taking in to account specific species, climate and age of the tree.

What are your thoughts?

While I'm not dealing w/ anything in-refinement, only in-development, I can't comment from experience but would say that your thinking is kinda 'cart before the horse' here, insofar as trying to put a # on it when in reality it's merely a # that's derived from the "bearing in mind" items you mentioned... I was actually doing this myself recently in a slightly different way, in that I was trying to discern when was the best "time", on a calendar, to start collecting BC's this year - I quickly realized that I'm not looking for a date, I'm looking for a set of conditions, so putting a hard date on that is about as useful as putting a hard time-period on re-potting as your premise here aims to do, I think it is inherently&always "gonna depend"!

Neat to hear/speak to anyone who's got enough mature trees that they're thinking of such things, you wouldn't happen to have a site or photo-hosting account of your stuff that I could peruse would you? In any case best of luck w/ everything!!