AusBonsai

Hi all, Got a few of my maples with leaf issues at the moment. I'm really hoping it's not bacterial leaf scorch but i've not had experience with it before so hoping others can shed light on it. They've been hit with Powdery Mildew in the last month or two but this is new for me.

Anyway any help is appreciated, photos for reference.

Has it been hot? I’m no Japanese maple expert but they may just be sun burnt.

Not particularly, the new leaves come out and immediately turn start turning brown

I have the same thing, im hoping it is just sun/windburn but has been quite wet lately

Dan.E - I actually dropped in to a Bonsai Nursery and spoke to the head guy there who i have a pretty good relationship with and he was confident it's just a case of it being too wet and potentially needing to be repotted, cleaning out the roots creating space for air and full change of soil this year. He said that he repots his Japanese Maples every 2 years and if he lets it go 3 years he runs into these issues of holding too much water and the health going backwards.

Hopefully that's just the issue and both our trees look better come spring!

thanks for the info Tims ,mine are in nursery pots and potting mix and diatomite just for trunk development and are obviously staying to wet

I agree the trees are staying too wet. It is essential to provide maples with very good drainage.
Roger

Thanks Roger, good to have another person agreeing with the diagnosis. I've backed my watering right off so come winter i'll give them a good clean out and repot them freshly

are you repotting now Tims or are you going to wait until leaf drop?
and what sort of mix are you going to use I am trying diatomite ,pumice, zeolite mix for more advanced trees but was thinking of pine bark ,perlite, bit of coir and a little diatomite and some potting mix for developing stock ?

I moved one of mine that was way too wet and had a very dense root ball into a grow box i kocked up out of old fence pailings and used a chop stick to create some air channels, and another one was in a pot that had the interior glazed as well as the exterior which i have no idea why anyone would do that when glazing a pot, but i've moved that into anther pot and teased the roots out a bit.

I will wait until winter to properly root prune them and do a full repot for sure though, but when i pulled them out and saw how wet they actually were i didn't want to leave them in the pots there were already in all through the wet months of winter.

thanks for the info Tims i was thinking of just slip potting also ,what sort of mix are you using?

No problems Dan,

I'm just using a generic bonsai mix from my usual bonsai nursery which seems to be part small stones for drainage and part composted organic like pine bark though i'm not sure exactly what it is. It seems to break down after 3 years at most so i guess that's how long these trees have been in these pots given i purchased them only last year. I got my hands on some Akadama recently and i'm going to move a few trees into that to see how it goes this year though.

You need to be careful when slip potting trees to improve drainage. I know it seems like you are giving plenty of space for the excess water to drain to but the reality is that it is difficult for water to pass from a dense zone (the old rootball) to a less dense zone (new potting mix) and in many cases the old roots actually stay wetter after slip potting. You should monitor the old zone closely to make sure it does not stay too wet in the new, larger pot. Make sure the pot is up off the ground and in a place where air can move around and through the pot to help it dry out a bit.

thanks neil

Thanks Shibui,

They are up on my benches that have good air circulation and i did what i could to gently create air channels in the old root ball. I have noticed since i did it that they don't look as bad as they did, or at least are not continuing to go backwards in health terms and I've backed my watering right off as well. So far seems to be going well but i'm keeping a close eye on them.