Japanese maple leaf problem

Discussion in 'Maples' started by Riverdale27, May 24, 2021.

  1. Riverdale27

    Riverdale27 Active Member

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    Hi all,

    I started collecting japense maple trees this year, so I bought about 15 of them in the same nursury, plan ot grow some mother trees in containers, and start sowing and grafting in the coming years. I planted all of them in 25 liter containers in a mix of potting soil, peat and pine bark.

    Its been quite wet and cold for the time of year. In fact, the weather has been quite bad all spring, with the coldest april since I've been born.

    I'm starting to notice problems one some of my acers, more specifically my Palmatum Bi Hoo is very badly damaged, and my Shirasawanum Aureum and Jordan are starting to show similar signs.

    I'd like to know what it is, and what I can do about it, and if I need to be worried these young trees might die from this. After all, it was quite the investment... My trees are about 40-50 cm.

    Thanks for helping.

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  2. Acerholic

    Acerholic Paragon of Plants Forums Moderator VCBF Cherry Scout Maple Society

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    Good morning and welcome to the maples forum. Before we start to discuss your maple problems, you need to upload your photos as they are not showing on your posting for members to see.
    Here is a link that explains how to do this.
    Attach photos and files
    Next the maples you are asking about are the problematic ones IMO.
    Especially Bi-hoo that suffers greatly with die back. All you can do with it is cut out the dead or diseased branches and give it time to settle in it's new environment.
    Now for the two Shirasawanum's Jordan and Aureum, both of these can be affected by sudden changes in temperatures and after this awful Spring, where there have been many frosts, then these will show signs of stress. But IMO they will recover over the next 6 weeks when you will see a second flush of leaves.
    But as we can't see the photos yet, it is hard to give a positive idea of your problem.
    I'll await your reply with photos.

    D
     
  3. Riverdale27

    Riverdale27 Active Member

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    Hi Acerholic and thanks for your help.

    Here are the pictures, attempt 2 :)

    An unrelated question: are all messages here up for moderator approval, or it that just because I'm new?
     

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  4. Acerholic

    Acerholic Paragon of Plants Forums Moderator VCBF Cherry Scout Maple Society

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    Because your new, they will come to moderators initially.
     
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  5. Acerholic

    Acerholic Paragon of Plants Forums Moderator VCBF Cherry Scout Maple Society

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    OK IMO you may have two things going on here, firstly frost damage to the new leaves and then then the start of powdery mildew that often starts with black spots on the leaves. Now if you had an exceptionally dry Spring and we did here in Southern England so I expect you did in Belgium, then this is an ideal breeding time for this fungus.
    Those leaves will drop, but if it were me I would remove them at the base and destroy. Also any leaves that have already dropped. 'Leave none behind'.
    You then need to consider spraying for powdery mildew. This is up to you what you use. Some use Neem and others use fungacide sprays that any garden centre will sell.
    Next, do give your new maples space for air to circulate. This is a sure step in preventing further problems.
    Hope this is of help.

    D
     
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  6. maf

    maf Generous Contributor Maple Society 10 Years

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    Personally I wouldn't use a container anywhere near 25 litres for a new young 40cm Japanese maple. Much too much soil volume, the mixture will stay too wet for too long, especially with the spring this year. I'd be looking at putting them in 7 or 10 litre pots for a year or two first. Even better, go from 7 -> 15 -> 25 litres, allowing 1 or 2 years in each of the intermediate sizes. Also I would add a bit of grit and perlite to your potting mix. Drainage is king.
     
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  7. Jaybee63

    Jaybee63 Rising Contributor Maple Society 10 Years

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    I’m with Maf on pot size. It’s a fact that Japanese maples don’t like overpotting.
    And also with Acerholic on frost damage.
    I know mine have suffered with the unusually late frosts we had in the south of England.
     
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  8. Contact82

    Contact82 Member

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    I'm fighting the same problem on some maples, I agree about a consequence of late frost. In these cases I usa a PK 20-30 fertilizer to strengthen the leaves tissues and to help resistance.
     
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  9. Riverdale27

    Riverdale27 Active Member

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    Hi guys,

    Thanks all for the feedback. I'd like to ask some more questions.

    My own guess, based on reading in my book on maples by Vertrees, was anthracnose. It says its a fungus that shows up in cold wet spring weather that start with brown spots and then irregular patches. Seems to match exactly the situation, but its always very hard to tell. The reason why I wasn't thinking about mildew is because I don't have the white stuff on the leaves... maybe that would only come later? What do you guys think?

    I have Compo Duaxo at home, its a fungicide against powerdy mildew, leaf spot, scabies, rust (or at least those are the Google translations of the Dutch name of the diseases). I probably can't do anything wrong with just spraying that?

    About the pots, I've posted some pictures below. The plants already came in quite large containers, so I'm not sure... it doesn't look very large to me. Maybe the pictures give a better view? You can see my Orange Dream, Jordan, Aureum, Katsura and Bloodgood. They look quite "normal sized" for their pots?

    And if it still is too large: is it required to repot? Would be quite the work indeed :)

    Best regards,
    Kurt
     

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  10. Riverdale27

    Riverdale27 Active Member

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    Oh and one more thing: we haven't had any frost here for, let's say, the last 3-4 weeks, and if we had, I would put them in the greenhouse.
     
  11. Acerholic

    Acerholic Paragon of Plants Forums Moderator VCBF Cherry Scout Maple Society

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    It won't do any harm at all to spray K.
     
  12. Acerholic

    Acerholic Paragon of Plants Forums Moderator VCBF Cherry Scout Maple Society

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    They do tbh, and although in full greement with the others about not going too large when re potting. I would now not carry out any re pot with those maples for at least two years.
    They do look lovely BTW.
     
  13. Riverdale27

    Riverdale27 Active Member

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    I just sprayed all of them with Duaxo... and put them in the greenhouse or under the roof of my terrace
     
  14. Acerholic

    Acerholic Paragon of Plants Forums Moderator VCBF Cherry Scout Maple Society

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    Watch and wait time !! But I think they will be fine.
     
  15. maf

    maf Generous Contributor Maple Society 10 Years

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    Hi, the maples are a bit larger than I was expecting from the original post so not as over potted as I thought. I would still have gone a little smaller especially on the slower growing ones. Other people have a different approach than me and would go straight to that size. If the potting mix is free draining enough (and it looks to be from what I can see in the pics) they will be fine.

    One problem with relatively large pots is that it can sometimes lead to fast growth and that usually means soft growth that will be susceptible to branch die back next winter and spring. They have probably come out of a commercial greenhouse and so are not yet acclimatised to outside winter temperatures. To try and discourage the soft growth don't feed them any extra nitrogen this year just micros, and maybe some P and K if you think they need it.

    Good luck, you have a nice selection of maples.
     
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  16. Otto Bjornson

    Otto Bjornson Contributor

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    sometimes one can love their maples to death.
    Japanese maples really require very little other then good drainage and water. Over fertilizing can lead to that form of leaf die back in your photo's combined with too large a pot that would encourage faster then normal growth rate. I personally don't recommend any fertilizer application in a garden landscape, only one tablespoon slow release when in a container growing medium ( once a year in spring).
    The specimens in your latest photo's look very healthy. And those pots would be fine for at least 2-3 years or more before thinking of re potting imo
     
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  17. Riverdale27

    Riverdale27 Active Member

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    Hi Otto,

    Thanks for your help. I've been feeding them a weekly dose of fertilizer for sour-loving plants. It's a solution that has about 7 nitrogen in it. You solve it in water and I give all my plants a little bit of water with this in it. Like 1 liter per plant I would say. Could this maybe be the issue?

    The reason why I do this, I because I've been hearing MrMaple on Youtube talk about how to water your plants, and they say a weekly dose of up to 15 nitrogen is recommended, as long as you stop in time for new growth to turn into wood. So now I'm confused :)

    I did just rewatch and heard them say every 3-4 weeks... so whoops about that one :)

     
  18. Acerholic

    Acerholic Paragon of Plants Forums Moderator VCBF Cherry Scout Maple Society

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    Just read this and thought Oh no !! Maples rarely need feeding IMO. I give a slow release granular feed 'Once' only in Spring and that's it.
    I know that some nurseries give feeds at a regular basis each year, but they are trying to get a lot of growth to be able to sell their trees.
    Once you have them at home in your garden, then IMO they do not need this. All you will get is whippy weak growth if you carry on with feeding.
    Others may disagree, but those are my thoughts K.
     
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  19. AlainK

    AlainK Renowned Contributor Forums Moderator Maple Society 10 Years

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    I second that.
    I think nurseries fertilize a lot to boost the growth of their trees so they get bigger faster for the sale. But it is not necessary when the trees are in your care, unless the pH of your soil is high (alkaline), "J. maples" preferring a (slightly) acidic soil. If the pH is too high, they will have chlorosis, which weakens the tree.
     
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  20. Riverdale27

    Riverdale27 Active Member

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    OK, this is very clear I think. I'll stop fertilizing immediately. I contacted the nursery as well and they also asked my first: did you fertilize? :)

    Let's see in a few weeks where we end up.
     
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  21. Acerholic

    Acerholic Paragon of Plants Forums Moderator VCBF Cherry Scout Maple Society

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    Well done K.
     
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  22. Contact82

    Contact82 Member

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    Of course I agree that JM needs really few fertilizer, even if it depends IMO on which kind of soil you are using...For sure is not appropriate to use high Nitrogen fertilizer that give a big grow but a fragile health too, but PK in my experience can help. I don’t know if others do it, but I use some supplements too during the growth season and they can help in maples health.

    clearly this is only my experience :)
     
  23. Riverdale27

    Riverdale27 Active Member

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    I think for the coming years, I'll probably do an organic slow release 10-4-8 NPK grannular mix (it's called DCM Mix 5) in April and then stop with that.

    Or would you guys recommend doing nothing at all?
     
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  24. Otto Bjornson

    Otto Bjornson Contributor

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    Unfortunately I would say it is definitely the problem.
    When we had our maple nursery in operation we only used osmocote 16-10-10, 6 month slow release fertilizer. And as mentioned, one tablespoon regardless of pot size. With the exception of only a teaspoon in one gallon pots.
    Maples are sort of like a cat, just leave them alone other then your regular watering schedule and they will do fine
     
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  25. maf

    maf Generous Contributor Maple Society 10 Years

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    Sounds like a good plan.
     

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