Yellow foliage on Mountain Hemlock

[Jphipps]

I bought about 7 Mountain Hemlock trees in early spring and repotted all of them as they were badly root bound in their containers. 3 have bounced back amazingly and have exploded with new healthy foliage.

The others have needles that turn yellow and have been slowly shedding these since the spring. They have some new healthy growth but this process of yellow needles dropping continues. The healthy ones are not exhibiting these symptoms. The yellow needles are dispersed throughout the trees except for the very tips of branches.

I can shake the branches and several yellow needles fall right off.

Also, one of the trees has a general yellow tint to the entire foliage.

Thoughts to the cause or treatment recommendations?

 

[MrFancyPlants]

Check with @River's Edge , but could it just be the older growth aging off? Maybe some fertilizer and more light to stimulate more fresh growth?

 

[River's Edge]

I bought about 7 Mountain Hemlock trees in early spring and repotted all of them as they were badly root bound in their containers. 3 have bounced back amazingly and have exploded with new healthy foliage.

The others have needles that turn yellow and have been slowly shedding these since the spring. They have some new healthy growth but this process of yellow needles dropping continues. The healthy ones are not exhibiting these symptoms. The yellow needles are dispersed throughout the trees except for the very tips of branches.

I can shake the branches and several yellow needles fall right off.

Also, one of the trees has a general yellow tint to the entire foliage.

Thoughts to the cause or treatment recommendations?

I would suspect root stress from the repotting process! I would leave the trees to recover! Morning sun afternoon partial shade. Hemlock require careful repotting until established with fine feeder roots! Usually a slower transition from nursery pots and typical root mass from nursery soil.

 

[Jphipps]

Thank you Frank!

 

[River's Edge]

Thank you Frank!

Hemlock are best repotted segmentally during the initial transition. Think of it as a pie cut into six slices. Do two opposite slices or two side by side at one repotting session. Start with the areas of weakest root growth, leaving the strongest for the last repot. This way you have strengthened 2/3 of the root ball before removing or working on the healthiest natural section. Remember you are changing the basic root structure to more of a feeder root structure to thrive in a bonsai pot. Typical nursery root structure is less divided, as is collected root structure normally. Hope that makes sense!

 

[Jphipps]

It does. I went pretty aggressive on these trees during the repot as they were very root bound and super neglected. I could hardly saw through a couple of the root balls. They were terrible.

The foliage was also covered in moss that was killing branches.

They are all roughly formal upright trees that I'm planning a future forest planting.

 

[River's Edge]

It does. I went pretty aggressive on these trees during the repot as they were very root bound and super neglected. I could hardly saw through a couple of the root balls. They were terrible.

The foliage was also covered in moss that was killing branches.

They are all roughly formal upright trees that I'm planning a future forest planting.

Please understand that you must carefully sort the roots as best you can in each segment. Take care to undo obvious circling roots on the outside before working segments. Unfortunately root bound nursery stock that has been repeatedly up potted is the worst case scenario to start from. This is where it really helps to start from the weakest root areas first if any exist. The use of a segmented approach helps to alleviate damage by limiting it to part of the root ball.

 

[Jphipps]

I'm not sure if my method adheres to this strategy or not.

This is a stock photo but an example of what I did to the roots.

I sawed the rootball down to a manageable depth (red dashed line) and trimmed the outside edge of the rootball, circling roots and long scraggly ones included. I didn't do anything to the rest of the root system (indicated by the blue/green markings). Is leaving that inner area untouched a safe initial repot method or a method resembling what you posted above?

 

[August44]

WOW! That is a serious chop IMO. Not real experienced, but I would never chop anything I liked that much. The rule as I know it is 1/3rd of the roots or 1/3rd of the foliage in one year, but never both in the same year. I'm sure there are deciduous that can handle more, but a MT Hemlock???

 

[MrFancyPlants]

Yeah, that looks pretty harsh, but they may pull through. I think keep it shaded during the hottest part of the day until you see signs of new growth.
I think light fertilizer wouldn’t hurt your chances, but it is nearly a shroedingers bonsai with that many roots removed. Sometimes the nursery stock had a buried trunk so that the roots emanate from the bottom half of the pot. If you blindly saw, you can remove all of the roots. Better to take a pie shaped wedge as suggested and then saw of a portion of the bottom in stages depending on what you find.

 

[Jphipps]

The majority of them were essentially a brick of roots completely filling the nursery containers. Using a large saw, it was a serious battle to even get through each root ball because they were so compacted and root bound.

They were badly neglected with foliage covered in moss that was also killing the branches. I've since eradicated this problem by spraying with a 1:1 of Vinegar and Water and removing the dead moss by hand.

They were $10 each but each one had enough character hiding in there that I went for it. I would have to count again, but I believe I bought 7. One died. 4 are thriving and 2 are still struggling to bounce back. Those 2 pushed out new growth but the needles that turn yellow then fall off are the concern.

 

[sorce]

One died. 4 are thriving and 2 are still struggling to bounce back.

If you were in Vegas you'd be ....yeah maybe that's not an appropriate analogy!

You won the numbers game.

That's all that matters.

Sorce

 

[August44]

Possible to see pictures of the 4 that are thriving?

 

[River's Edge]

Is leaving that inner area untouched a safe initial repot method or a method resembling what you posted above?

No it is not what I recommended, or close. You are very fortunate to have some survivors! I can only suggest you were lucky and the trees were very young! Based on your picture you removed over 2/3 off the bottom before starting anything else.

 

[Jphipps]

6 survivors. Only 3 in good health. Wired one out recently. If they all recover, my plan is to incorporate them into a forest planting.

 

[August44]

Do your nurseries up there generally have these trees in stock? I'd like to get a bigger one like the size of yours. Can I assume that they will not bud back and grow new branches where those stubs are now or anywhere else?

PS: thanks for the pictures

 

[Jphipps]

No problem! They won't back bud on the branches that have no green left. I'm planning on eventually removing those completely or turning some of those into jins. The other branches should back bud if healthy.

I found these through a Craigslist ad. They were on consignment from a small family owned nursery that shut down. There wasn't much left once I got there. This was early spring of this year. There were much bigger ones than these but I'm sure they are long gone by now. Super cheap prices but they were in ill health. Healthy Mountain Hemlocks averaging 3-5 ft tall at regular nurseries around here are normally $80-$120 each.