How to Avoid Burned Leaves on Deciduous Bonsai

Preventing burned leaves on deciduous trees in the summer involves two things: 1. We need a lot of fine roots. 2. We need to water frequently. Let’s break that down a bit.

If we don’t have a lot of fine roots, it won’t matter how much we water because few roots won’t be able to support the water needs of the tree at 95 F/ 35 C. If we overwater before we have many roots, we won’t get many more to emerge. And if the tree is in a poor soil mix, we won’t get many fine roots for that reason, too.

If we do have a lot of fine roots, and yet don’t water more than once a day at 95 F/ 35 C we will likely get burned leaves on our beeches, maples and other deciduous trees anyway. On a hot sunny day be ready to water 3 times a day. If your lifestyle does not allow that, then set up a watering system for the one or two watering cycles that you can’t do by hand.

Both of those requirements must be met to prevent burned leaves. Take a look at these photos:

This is the soil of the Japanese maple also shown in the next shot. There are many fine roots all the way to the top of the soil surface. They even climbed up and went into the fertilizer pellets on the surface. That kind of fine root growth is what you want to prevent burned leaves. If you don’t have fine roots bumping happily along the top surface of the soil and through your moss you can be sure it has not colonized the pot and it is only growing along the sides of the pot, which is the worst place for them. On the sides they will get scorched by sun hitting the pot, and will suffocate in a pool of water at the bottom—and that is a very unhappy and unstable tree.

Japanese maple, Acer palmatum, at the end of August.

Red maple, Acer rubrum, at the end of August.

9 Comments

  1. Dylan says:

    Great post (and recent frequency of post). I was thinking my maples were getting too much sun because the soil always seemed wet but the leaves were getting the edges singed. I think this cleared up a lot. Thanks for the Juniper article as well, I was definitely confused about that bit of information as well.

  2. art rodriguez says:

    michael
    do we get the fine feeder roots to grow above by spreading some sifted spagnum moss ?

  3. G.Hues says:

    I think I need to add more pumice to my mix …for my maples…..I’m assuming you use a fair amount in your mixes?
    Cheers Graham

    • crataegus says:

      Yes, I do use a lot. Depending on the tree, I can use as little as 30% pumice or as much as 70%. For the maples I would say about 50% is a good starting place. If you grow pines you might well wish to use a bit more pumice. But if you’re using akadama as your secondary particle you don’t need to worry about soggy soil, really.

  4. Alex says:

    Hey Michael, do you keep any of your maples underneath shade cloth?

    • crataegus says:

      I haven’t, but I think it would be a good idea even in the mild summers I have. Just 20% softens the direct sun. In Japan we did have shade cloth over the deciduous, but the summers there were more intense.

  5. Al says:

    Hi Michael, i have two Bloodgoods 6′ high 20′ apart facing south west in the cooler area near San Francisco. Planted last season. The dirt down deep is clay! They are doing very well except at this time the leaves get scorched possibly by sun and continuous light breezes from the bay. I have defoliated them and i know they will bud again prior to winter.
    1. Do you think more frequent watering might help? I might start doing that 3 times a day! I see other maples in the sun not scorched and i see some in semi shade… scorched.
    2. Their leaves are usually green underneath but one of them just turned all leaves green. Why?
    Both trees come from the same source.
    If you go to flashknow.com you will see a Yin Yang i just built. There i have a Hefner maple in each center. Being in the back yard they do not suffer as much as the Bloodgoods. Anyway, thank you very much in advance. Have a great day!

    • crataegus says:

      I don’t have much other than to agree with you that possibly more watering might help. But if they’re in the ground, periodic deep watering is the way to go. Not sure what the color shift is that you describe, other than the Bloodgoods can have green areas occasionally here and there.

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