Chojubai Notes: Part 3—Why is my Chojubai weak?

Few plants come without a puzzling issue or two. For ‘Chojubai’ Dwarf Flowering Quince, the most serious issues are in the roots. Chojubai are strong plants that will normally extend 6” (to 18″) per growth surge. If this is not seen, then be on the alert.

A weak tree will not make typical extensions in the spring and might have a yellowish color. Some weak Chojubai are simply in soil that is too fine, are overwatered or underwatered, or are in pots that are too shallow, and those are easy to correct.

Otherwise the root zone of a Chojubai is susceptible to several problems that can weaken your tree. The first is a nematode, the second is a bacteria, and the third is a root gall, and they’re all separate but interrelated parts of the disease known as crown gall. It’s not frequent, but if you have a Chojubai, be on the alert for general weakness. I’ve been looking into this problem for a while, and my apprentice Bobby has been very helpful in discovering some of the links too, so I’d like to offer here what we’re doing now to tackle these root issues.

  • In a quick summary, root lesion nematodes cause wounds in the Chojubai’s fine roots that provides an entry for a truly rascally bacteria, Agrobacterium tumefaciens, which causes crown gall. A wound from a root-pruning tool can also provide entry. The bacteria lives inside the root, and transfers part of its DNA to the DNA of plant cells, which, with cell division, cause the callus-like galls we see on the roots of affected plants. So the bacteria is very sneaky fella, and not too easy to get rid of!

First, there was a nematode… named Nibble.


…then there was a bacteria…named WisFree…


…and lastly there was a gall…named Warty. And they all had a rockin’ party in your pot. Keep reading to discover what mickies to throw in their drinks…

If you see galls (Warty and friends) on the roots of Chojubai, try these treatments:

  1. Shift the tree into a bigger pot. If the weakened Chojubai is in fine soil, a small pot, compacted soil, or a shallow pot, definitely transfer it to a deeper, larger container or box with coarse pumice (1/3” + size) or similar on the bottom and sides surrounding the original soil mass. Let it grow freely, without overwatering it (algae and liverwort are the clues), while controlling the other issues.
  2. Control the root lesion nematode. There are nemacides specific for the control of nematodes, and these may be used. With a suggestion from a friend and a couple of tests I found that soaking the root ball in Zerotol at 1.25 oz / gal will kill the nematodes. This can be done while the tree is still in the pot.
  3. Control the bacteria. The problem with the bacteria is that it’s inside the root itself. Copper is effective for this bacteria, (the Japanese bonsai professionals use Streptomycin, but it’s puzzling to figure the proper concentration for plants since they are made for internal use with animals). I’ve been using Phyton 35, which is a systemic copper bactericide/fungicide. Be sure to read the label carefully—Phyton 35 requires a change in the water we mix it in to a pH of 5.5-6.5.
  4. Control the gall. Cut the gall away with pruners when repotting. It may take several repottings to get all the gall removed.

What seems to be important is to take care of this three-ring circus systematically. First knock out the nematode. Then go after the bacteria. And finally cut away the gall. Even if you’ve killed your nematode and the bacteria, you may still have the gall as the DNA from the bacteria will keep replicating with cell division. But if you’ve killed the nematode and are controlling the bacteria, a weakened Chojubai often shows a very rapid jump back into strong growth. I’ve seen new, large, strong leaves and even shoots on a totally stalled Chojubai in under two months with these treatments.

The nematode is often the primary culprit, which appear to think that Chojubai roots are like crack cocaine, chocolate, nirvana, or all three. They can knock down the root system of a quince quite rapidly, and then you see a weakened tree with a gimpy root system that does not have the typical vigor of Chojubai. Many other Rose family plants are particularly tasty to nematodes.

A few of the nematodes you can see without a loupe (I’ve seen some about ½” long, and look like glassy worms), others are nearly microscopic. If you find the gall you can assume you’ve got the bacteria. Prevention is best, such as being careful about sterilization of cuts, and controlling the nematode.

Hopefully you’ll never see galls on your tree, but if you do, try these remedies to bring your tree back to health!

A few older posts about ‘Chojubai’ Dwarf Flowering Quince:

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  1. nelibonsai says:

    Thank You very much….going to repot my chojubais today…I got them from Japan last October but I have seen almost constant flowering (Africa) and fruits (i remove them) but not much growth. I was away for a month and when I came back my chojubai had many leaves dropped and some half dry, but is still flowering. It is winter here, Does chojubai drop its leaves in winter? Can it be dormancy or my chojubai is not OK?

    • crataegus says:

      Ah, interesting, they might be confused for a bit if they’ve had to adjust to a new calendar. But they are so tough I doubt it will stress them much.
      Yes, Chojubai are deciduous in any mildly cool area. That is when they will tend to flower the most, so they really only go partially dormant in the winter except in the coldest places. They are very winter hardy. Sometimes you can see them flowering when the snow is still falling in late winter.

      • nelibonsai says:

        Thank for your Kind reply…I went to check on it just now…most of the leaves have dropped and the rest are hanging by a thread..But I saw buds fattening and one or two of them already opened, with tiny shoots.. It had one flower also which I promptly removed…So you think they are adjusting and that is why I have not seen much growth…any way, being a Sunday today, I shall repot them tomorrow, and post for you what I found in the roots…Do you think it is a good idea? Do you think they have adjusted already or I will stress them?

      • crataegus says:

        Probably an overly late reply…I’d let them adjust and see how they do. If they’re weak they’ll let you know. You can still do some control without troubling the roots. Or maybe just try repotting one and see what you find. If they’re weak but in loose soil—recently repotted—just let them go I’d say.
        Most Chojubai will drop leaves if stressed, and then regrow shortly thereafter if they’re in the growing season. If you’re warm in the winter, they might grow then too!

      • nelibonsai says:

        Thanks…This is my most vigorous chojubai in mid summer this year
        Would you say it is healthy? There are roots coming out from the bottom of the pot. I am not sure when it was repotted before…I brought it in Oct 2013 from Japan.
        This one has flowered all the time but I dont see much growth…I have not styled it yet until I see it is doing well.
        april 2014 6 month after arriving from Japan, and in mid summer here.
        This is the one that I dont feel is growing much.

      • crataegus says:

        The first tree looks fine. It appears healthy. You won’t get much growth in a pot that size though, consider using pots like that only for display. You’ll get much more rapid tree development in a larger, somewhat deeper pot. Maybe 3x that soil volume. Use coarse soil, primarily pumice or perlite, and sift out the small stuff.

        The second tree does look weak. I’d up pot that one too. Try to avoid those tall cascade pots, they are hard to use horticulturally, and trees don’t seem to grow well in them. Also, take all your flowers and developing quince off. That will also weaken your tree. On a strong tree we can let a flower go for a couple of days after it opens, then take it off before it gets old. When they die on the plant it stresses the tree.

      • nelibonsai says:

        Thank You! Will do that soon! Great advise! I will change the pot tomorrow

  2. nelibonsai says:

    Reblogged this on Bonsai advice and commented:
    Absolutely fantastic article on chojubai problems.

  3. Chris says:

    Michael, what a thorough and timely post. I repotted mine in spring, and has just languished all yr w. very little growth and no flowers. I’m sure I’ve got nematodes. I’m going to up pot it today into pumice and track down some zerotol and phyton…boy, not cheap stuff.
    Anyway, Thanks Michael for the informative blog post.

    • crataegus says:

      Good luck and let me know how it goes. Go in with a friend, that 2.5 gal. zerotol is not cheap… useful for weird things like this.

      • Chris says:

        Thanks Michael. I shifted into lg grain pumice on the 3rd and there’s actually some new growth happening already! Very unexpected. I just got the Zerotol last night so I’ll be doing the drench today. The Phyton is coming tonight. Should I do all this in one day Michael, or wait a day-week b/w the Zerotol and Phyton treatments?


      • crataegus says:

        Hi Chris,

        That’s the kind of responsiveness Chojubai is known for.
        Are you sure you have the disease, though? Did you see the galls? Or nematodes?
        Definitely space out chemical controls by at least one week. And that’s for a severe problem. Usually 10 day cycles are best. If you did not see any root problems, it may be that you consider a prophylactic program, using these two just rarely.
        It’s possible that the tree just wanted larger soil size. Much greater vigor will be seen with Chojubai with about half the bottom of the pot with only large size pumice, and your more normal mix above that.

    • Chris says:

      I looked for over 20 mins Michael poking around the peripheral and didn’t see any nematodes nor gall. I was surprised not to find anything, and the roots looked pretty healthy too. (This spring, I used the medium sized Akoi mix and med. sized Akoi/pumice as bottom layer.) Though the symptoms were exactly as you described. It’s not grown hardly at all this yr, very stagnant.

      Thanks for the advice Michael! I’ll wait 10 dys and do the Phyton next and then just watch carefull the rest of the growing season. Oh, when should I restart ferts?

      • crataegus says:

        If the soil was dense with roots than it might have been just that— once the tree gets into coarse pumice, or similar, it will change dynamic very fast and begin growing again. If they are not repotted for a while they slow down to the point of not growing more than the whorl growth and no extensions. So, perhaps that was it.

        Chojubai like fertilizer, so in a couple of weeks more you can begin that. If the tree is old enough to have bark already, then keep it on the low side as they will shed their bark easily if over fertilized.

      • Chris says:

        Michael, how long should I leave this chojubai in the pumice mix? Recovered nicely…Thanks again!

        And, I did 5 lignified cuttings this yr. Kept in shade for about a mos., and put in full sun and all but one died. I know you’re extr. successful in propagating them. What am I doing wrong?

      • crataegus says:

        One or two years would do it, for the pumice mix-

        As for the cuttings, if you’ve not got a greenhouse or misting system your success rate could be about one in five. Many factors contribute, though. But first let me suggest a mist system even if you’ve only got outdoor space. That way the plants can be in more sun, and they’d get misted every hour or so. Ween the cuttings off the mist slowly. Move them over an inch every two days, for instance.

        Factors to consider: Maybe you moved the trees into sun too fast. I usually have them under shadecloth in the greenhouse for a full growing season.
        Size of cutting. The larger the size of cutting the lower your success rate, the small tip cuttings of 4″ will have very good success.
        Size of soil mix. This is where you can use your ‘fines’ that are usually thrown away when sifting. Nearly anything can work, really, for starting cuttings.
        Strength of tree that the cutting was taken from. Make sure it’s a strong tree, and the cuttings are of the strong parts.
        Timing can help, June is about right for taking the cuttings. With Chujubai almost any month of the year will get some rooting success, though, although your numbers might be lower.
        Chojubai will root without hormone just fine, but more roots will come with some hormone.
        Try those, and see if you get better results!

      • Chris says:

        Thank You So Much Michael for the cutting info!!
        I did use a misting system actually, and why 4/5 made it thru this part. From what I gathered from your post though, I lost them b/c I put them in full sun after being misted under 70% shade cloth for 5-6wks. You keep yours under the shade cloth for a full yr! Boy, no wonder they died pretty quickly. (I thought being a full sun lover that the cuttings would show the same characteristic) From what I recall, your greenhouse is prob. a 30-50% shade cloth. I should track down some 50% to use under the misters.

        Anyway, Thanks again Michael for your help!!

      • crataegus says:

        Ah, I see—if you have a misting system, and you calibrate it carefully, you can grow cuttings in full sun and get very good and rapid results. No need for shadecloth. But a thinner shadecloth, like 30%, and mist would be very good too.

      • Chris says:

        Hi Michael, I thought you’d like an update. This yr., it shed all it’s leaves for the first time, so I was somewhat expecting it to be dead. But it’s budding out like nobody’s business. I did loose 1/2 of a major old stem that has messed up the clump’s design. But it’s alive lol

        Thanks again for your help. I just plan on repotting back into Akadama next yr.

      • crataegus says:

        Sounds like good news. Chojubai generally don’t need repotting more than once every 2-3 years. Many don’t seem to fill their pots with roots even in that time.

      • Chris says:

        Thanks Michael. Just more care involved being in pumice alone, so I’ll look forward to the day I can get it back into akadama. Really appreciate the help Michael!

  4. As always, great information! I don’t know if this will be useful, or just get a laugh,

  5. monte says:

    Interesting, when I’ve looked up this disease I’ve always found articles citing one of these causes for the problem, this is the first time I’ve read of them all together, thanks.

    I have this happening to a developing apple trunk, this spring as an experiment I inoculated the soil with an oyster mushroom mycellium that traps and feeds on nematodes.

    • crataegus says:

      That’s what I found too, part of the problem but not the whole thing. Curious about the mushroom! There’s also a beneficial bacteria that is protective to the pathenogenic bacteria, but it’s bioengineered and that made me skittish.

  6. Daniel Dolan says:


    Here is a question I do not recall anyone asking ……….

    How do you pronounce, Chojubai? [Accent on which syllable? 2nd?]

    I have searched on Forvo, an online pronunciation guide for almost 100 world languages. As Chojubai is a proper name, I assume, it was not listed.

    Thank you.

    In your opinion, what would be the most visible difference between Shimpaku Juniper foliage styled in a, lets call it, Classical Japanese Manner and one in which the foliage is treated according to the, not precisely defined, Naturalistic Manner?



    • crataegus says:

      Cho-jew-buy, relatively phonetic
      as for accent, if any, there is a slight drop on the last one.

      Juniper question is hard to answer in words. I think you’d see in the Naturalistic style the soft cloud forms that would be the eventual result of the more refined padding of the Japanese. Eventually they would be similar. The only major difference would be if you looked up into the tree’s organization of the branches and twigs, you’d see different structure.

  7. minxuslynxus says:

    Hello! I recently acquired a young Chojubai and am looking for care instructions. I found your blog and what you write about it is very interesting, thank you for sharing all this useful information! I bought it last week but I think the pot is too small and the soil is entirely covered with moss which makes it impossible to see if it’s dry or not. I think it’s still a very young plant. I would like to repot it but I don’t want to screw it up so I would like to know when is the best time for repotting, and if I can let it grow unrestrained for a while after that? (pity I can’t show you a picture here). Thank you for any advice!
    Arigatooo from japan.

  8. minxuslynxus says:

    So kind of you! I left you message… thank you!

  9. Paul Parisi says:

    I found this on a “Neptune harvest” promotion. Great for us in the northeast but you must have something similar in the Northwest.
    ‘Crab & Lobster Shell is high in Chitin (Kite-en), which promotes the growth of Chitin eating bacteria in the soil. It will help eliminate Ants, Grubs, Fungus and Root Nematodes,’

  10. Paolo says:

    Dear me! Today, while repoting (Feb in UK I know!!) I found root galls in one of my crap apples. You did say ” controlling” does that mean it is not possible to fully get rid of it? Apart of using infected tools, How could be transfered into other trees? Do you keep the infected tree apart? Any updates on the treatment?
    Thank you.

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