Tips for Repotting-

Many of you are deep in the thicket of repotting, which I know can be one of those puzzling puzzles. This is just a short post on what I think are some of the big ones to not forget:

1. Don’t have your tree TOO dry before repotting. Although a bit easier for us, we would have a dehydrated tree just before cutting off many of its feeder roots—which ends up as a lose-lose bargain. Better to have it too wet than too dry.

2. As a general rule, don’t bare-root your trees. That’s for specialists doing special work and try your best to ignore the Japanese magazines showing someone boldly bare-rooting a 100 year old pine, or some silly blog like Crataegus Bonsai showing hosing of a deciduous tree. Bare-rooting probably kills more things than all others combined, so without the attending techniques, I would say don’t do it unless you’ve been taught how to, and which ones it’s ok to bare-root and which ones you should never do that way. Bare rooting is extreme, for extreme circumstances.

3. Sing while you work. Or at least put on some calming music, as repotting tense does not help us or the trees. (Singing is the primary job of apprentices, by the way. Evenings are usually taken up by long singing lessons, as to not dishearten anyone overly with poor vocals.)

repotting

4. Don’t refer to your repotting log to determine when the tree was repotted last and when next it should be repotted; refer to the tree. If a sharp chopstick won’t enter the soil easily in several places, it probably needs repotting. A weak tree for whatever reason might take three times as long to fill a pot with roots as a heathy strong one. Time is irrelevant.

5. Don’t cut too much root off a young tree or you can stall it’s momentum. And when repotting young trees in general, don’t cut the top much the year you repot.

6. Bamboo is your best friend. Drive shafts into very firm root balls for anchoring wires, or for bracing trees with really bad root systems. Get timber bamboo with walls about 1/3″ thick, and split it. You can see how bamboo is used in several places on this blog.

7. Have a REASON for repotting. If you’re just going through the motions because it’s what you always do at this time of year, well, rethink that one. Assess each tree and its needs. If you don’t know how to answer that, then find a teacher. No Star Trekking through your tree’s root systems, bolding going where no one has gone before…without a clue. Get clueified. Really. Repotting is like open heart surgery; we’re dealing with a tree’s life here.

20 Comments

  1. Tara says:

    Excellent tips! Thanks for posting.

  2. Sage Smith says:

    Nice little snidbits of useful information. I always look forward to your posts. I’m almost done with repotting hear in North Carolina.

  3. Timmi Kuykendall, Austin, Texas says:

    Thanks for the tips, Michael. I’ve repotted 26 deciduous trees, some for the first time in several years. They are beginning to bud out making me very happy.

  4. Jennifer Williams says:

    Thank you so much for the reassurance in what seems to be the trend for repotting, I am so thankful for knowing that I’m not the only one who sings when I repot….I’m a total “Trekker” and I’ve actually been thru open heart surgery many times over…as the nurse of course… It is quite comparable!
    Jenna
    Inland Empire Bonsai(IEBS) Spokane…and/or Phoenix Bonsa,i AZ.

  5. Connie says:

    Thanks for all the helpful hints. I am wondering less what I should be doing this time of year. It really has simplified my task. I am so glad you posted this. I now know I can safely put some trees off till next year.
    Connie from Chicago

  6. Steve Moore says:

    If there’s a way to reblog between WordPress and Blogger, I have yet to find it. So I posted a link, and your wish-I’d-thought-of-it-first picture! 🙂

  7. Chris G. says:

    Good guidance Michael!

  8. Graham says:

    Great timing for these tips Michael,
    Potting above the 49th on the pacific is well underway….can’t wait to see the results of using pumice.
    Cheers Graham

  9. Sandy R says:

    Enjoyed your repotting post. Had to laugh when I read it as I caught myself singing as I was repotting the other day. No telling what the neighbors and people passing by on the other side of the fences thought but my bonsai did not seem to mind.

  10. Daniel Dolan says:

    Michael:

    I always learn a lot from your posts…..I think.

    In my collection of 72 Bonsai Books I do not recall reading Item No.4 in your list of Repotting Tips…….the one about evaluating the need for repotting on the ability to penetrate the soil with a sharp stick.

    I do remember the benefits of repotting every 1-2-3 years [depending….] unanimously recommended by all 72 authors:

    1] Opportunity to improve drainage and ensure flow of oxygen / nutrients
    2] Improving the arrangement of top roots to encourage fine nebari
    3] Removing thick, long roots
    4] Inspecting for insects and fungi
    5] Removing areas of root rot which may have developed
    6] Trimming excessive root growth to encourage finer, more compact roots

    I realize these are the same people who recommended pinching juniper foliage …..hourly.

    Are your tips just for mature trees whose growth needs to be restrained?

    With a 10+ year old tree on which I am still developing trunks and branches…..don’t I want the vigorous growth that is encouraged by porous, fast draining soil? Therefore don’t I want to avoid soil into which I cannot probe with a sharp stick?

    Best regards,

    D/D
    Chicago

    • crataegus says:

      Marvelous questions—
      They point out the relative futility of writing a bonsai blog. There are always exceptions, and bonsai being more an art of exceptions it is difficult to teach without on-site training.
      But I’m game:
      All of those points are good ones…but they are applied on a per-tree basis. General comments like these—or the ones I offered—are only general. My comment about the chopstick is assuming it’s a bonsai, in a bonsai pot, and has some refinement. Then you are generally beyond the arranging of roots in the nebari and growing the tree hard, which is what will happen if we repot every one or two years. In fact, that is to to be recommended for very young trees where there is a lot of growth potential you’re trying to force—to get bigger trunk, grow branches and surface roots. Yes, repot those, in general, every two years. Grow two years, repot the spring of the third year. That’s how you keep the momentum of a young plant going. An old tree…now that’s a different story. If you repot an old tree every other year it never gets it’s feet under it, and may decline.

      Some of the old conifers are not repotted once in 6 or more years in Japan, and there’s a good reason for it. Old deciduous, every 3 to 4 years maybe. And we have such trees in the US now, and so if we do have older bonsai, if we don’t shift their repotting schedules we’ll never get the close ramification on the top because we’re continually making a very youthful rootsystem by repotting too frequently. I’m assuming the tree is in a volcanic soil mix of some sort. Organic soils break down and need attention, which is one of the reasons it’s very difficult to make truly refined and stabilized root systems in them. We’re continually screwing around with the rootsystems in those. In Japan, in a volcanic soil mix, the interior part of the root ball of established trees is often untouched for decades. Read that again.

      And we’ve not mentioned things like pot changing or angle changes or any of that stuff. Just necessary repotting.

      Also, the chopstick test in the soil should be applied only near the pot wall, not in the interior. Which SHOULD be tight.

      This is worthy of a post in and of itself…which I may do…

      Thanks Dan-

  11. Daniel Dolan says:

    Michael:

    Thanks for the effort………I think you have hit on it.

    On site instruction is the only way.

    I am leaving now and should be there in about 6 hours.

    Best regards,

    D/D
    Chicago

  12. Jim says:

    Can you please explain why it’s not advisable to bare root trees. For example,
    a collected juniper that has the original clay soil around the roots. Isn’t it better for the tree to hose off the old soil? Thanks.

    • crataegus says:

      Even under the best of circumstances, bare rooting a conifer and then giving it good aftercare like in a greenhouse, can result in losses. Given what I’ve seen, I don’t recommend it if you don’t wish to lose a tree now and then. Some would make it. But there is a much better option, and that is to do it in parts. Take it slowly, and over several repottings remove the old clayey soil carefully and gently with chopsticks. It takes time and effort, but that way there is a much reduced chance of loss. The danger in washing is that the water retained on the roots can prevent soil from falling into spaces, causing root air pockets. They are almost worse than clayey soil.
      Hope that helps a little-

  1. […] silly blog? Okay, it’s not really a silly blog. In fact Michael Hagedorns’ Crataegus Bonsai is one of the best blogs around. It’s just that Michael referred to it as a silly blog and it […]

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