Juniper shimpaku yellowing from inside

[jackeill]

I see some similar threads but want to make sure that my juniper is fine so that's why I post this. Will be very grateful for responses.

I have this tree for two years, it grows outside in central Europe (7a), I had quite nice growth during this time but this year around June I noticed the inner needles going yellow and then brown.This is first time it happens for me. I know that it is normal to some extent but now it lasts for 1.5 month and starts to worry me. I do not see any insects, I water it the same way last year, it just sits this way so it has a little bit more sun, but I know junipers love sun and the climate here is quite mild anyway so it is hard to really burn it. Besides, May and June were on the colder side this year.

If this is normal, should I manually remove yellowing needles? Some of the yellowing branches turn brown and lose all needles but when I try to pinch them they seem to be quite strong. Will they be getting new green growth then? How to asses that?

If it is not normal, what to do?

 

[Brian Van Fleet]

Mostly normal-looking shedding of old foliage. It does look slightly weak.
The circled tuft however doesn’t look normal…that’s possibly fungal.

 

[Shibui]

Lots of very healthy new growth on the tips of branches so I suspect no health problems but a couple of things to consider:
Trees will almost always put most effort into the outer foliage and tips of branches because those areas get most sun. Where resources (water, nutrients, light, etc) are in short supply, inner foliage is first to die off.
I suspect you have done very little or no pruning? To maintain junipers long term we need to prune and manage existing foliage. Just allowing free growth ends up with all the healthy foliage at the ends of long, bare branches. I have seen this internal yellowing and long, bare branches on some of my junipers until I worked out what has happening and looked into pruning and trimming more.

I water it the same way last year,

This sounds reasonable until you realise that, since last year, more roots have filled more spaces in the soil so every year it becomes more and more difficult for water to penetrate into the centre of the root zone. Also soil particles slowly decompose which also fills soil spaces and makes it harder to water properly. At some stage it becomes necessary to repot to give fresh soil and more space for new roots to grow.
Do you have any idea when it was last repotted and/or how much soil was replaced?

 

[BonsaiBonsai]

Can you show us a picture with the tree and the pot? Or in other words, how much of a squeeze was it already when you potted it last time?

 

[jackeill]

I suspect you have done very little or no pruning? To maintain junipers long term we need to prune and manage existing foliage. Just allowing free growth ends up with all the healthy foliage at the ends of long, bare branches. I have seen this internal yellowing and long, bare branches on some of my junipers until I worked out what has happening and looked into pruning and trimming more.

No pruning yet as I thought it looks good. I need to learn how to prune junipers. Is this good time to prune it?

Do you have any idea when it was last repotted and/or how much soil was replaced?

3-4 years ago, I do not know how much but the seller told me not to replace it for next 1-2 years. I believe it is due now?

Can you show us a picture with the tree and the pot? Or in other words, how much of a squeeze was it already when you potted it last time?

There is such an image attached to first post. I didn't repot it.

 

[Shibui]

No pruning yet as I thought it looks good. I need to learn how to prune junipers. Is this good time to prune it?

That's the thing with junipers. They look good but gradually deteriorate inside and suddenly you realise you've left it too long before cutting back shoots.
Best time to prune juniper is when it needs pruning. Time of year is not so critical so now would be OK.

3-4 years ago, I do not know how much but the seller told me not to replace it for next 1-2 years. I believe it is due now?

Should be OK. Juniper roots seem to grow relatively slow so repotting can be 2 - 10 years apart but lots of factors can influence that - age of the tree, how well it has been growing, type of soil (organic soil breaks down and needs replacing sooner than inorganics) Also depends how much original soil was left at previous repottings.
Just be aware that you will probably need to change watering each year to allow for more roots and soil breaking down.

I mentioned nutrient stress as a factor but forgot to ask about your fertiliser program. How often, how much and what fertiliser are you using?

 

[jackeill]

They look good but gradually deteriorate inside and suddenly you realise you've left it too long before cutting back shoots.

So when I cut the new growth the old growth will stay longer?

I mentioned nutrient stress as a factor but forgot to ask about your fertiliser program. How often, how much and what fertiliser are you using?

I use generic fluid fertilizer for bonsai. Every 3-4 weeks between April and October.

The question I have now is that there are some brown branches inside which do not have any needles now but seem to be attached pretty strong to the main branch. Will they back bud or won't they and I should remove them?

 

[Shibui]

So when I cut the new growth the old growth will stay longer?

Maintaining juniper is a cycle of grow and cut back. Longer parts are removed and replaced with some of the shorter side branches. Removing longer terminal shoots helps keep inner shoots alive, promotes new buds and replaces bare parts with the foliage on the side shoots.

I use generic fluid fertilizer for bonsai. Every 3-4 weeks between April and October.

That should provide enough nutrients for your tree so should rule out starvation as a cause of the yellowing.

The question I have now is that there are some brown branches inside which do not have any needles now but seem to be attached pretty strong to the main branch. Will they back bud or won't they and I should remove them?

Brown branches are almost certainly dead and unlikely to turn green but junipers usually have reserve buds hidden at the base of most branches. Those reserve buds will not usually grow while the branch tips are growing strong but when you prune the tips, that can stimulate those buds to grow.
Cut any brown branches but leave a short stub near the main branch. That can help those dormant buds to shoot.