# Canadian Hemlock problems "Need Help"



## vmachnig

I am having a persistent problem which I can use some help with. I have 50 canadian hemlock trees and most of then are doing fine however every year around this time one or two will drop all or most of their needles and eventually die. There is no apparent reason I can find, no signs of pest infestation, the trees on either side are healthy and it is really confounding me at this point as to what might be causing it. I can see no signs that they are in trouble before handle. 
I have one right now, it is about ten ft tall and has three separate trunks. one of the trunks has dropped all of its needles in a matter of days but the branches are flexible and still appear to be alive. the other two trunks are fine and show no signs of a problem. 

In the past when I have caught one at it's early stages of dropping it's needles I have been able to save a couple by doing every thing I can think of, spraying with insectiside fertilizing and continual watering but I don't know if one or any of the things I have done provides the solution or not. Initially when this first started I tried one thing at a time but I lost those trees when I did so and that is why I have done everything at once. 

All of the trees were planted about 5 years ago when they were about 5 ft tall and they are all about 8 to 10 ft now. They are planted along my property lines on three sides and not near the street so as to not be effected by the salt. the proplem is completely random and has happened in different locations and the trees to each side of the ones effected are healthy. It also is not necessarily the entire tree if it has mulpiple trunks. 

Any suggestions would be greatly appreciated.


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## PB

DO you have a picture of the trees? Pics of the branches (close up, and from a distance), the planting area and the surrounding area would be helpful.


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## vmachnig

PlantBiologist said:


> DO you have a picture of the trees? Pics of the branches (close up, and from a distance), the planting area and the surrounding area would be helpful.



OK, I just added some photos as you requested.

Thx,


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## PB

I noticed there is no grass under the trees. Have herbicides been applied or the area tilled up?


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## vmachnig

PlantBiologist said:


> I noticed there is no grass under the trees. Have herbicides been applied or the area tilled up?



I have used round up around them but that was last year in the spring. also after closer examination I noticed thatthe bark on the lower part of the trunks that have the problem is split if this might mean anything.


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## PB

vmachnig said:


> I have used round up around them but that was last year in the spring. also after closer examination I noticed thatthe bark on the lower part of the trunks that have the problem is split if this might mean anything.



I am guessing you killed the roots with Roundup.


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## vmachnig

PlantBiologist said:


> I am guessing you killed the roots with Roundup.



I could probably agree with that but for the fact that I used it around all of them and that the other two trunks coming up from this one are fine.


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## PB

vmachnig said:


> I could probably agree with that but for the fact that I used it around all of them and that the other two trunks coming up from this one are fine.



I would say that it is still related to the herbicide. You could have gotten overspray on the foliage and killed that part of the tree.


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## Metals406

PlantBiologist said:


> I am guessing you killed the roots with Roundup.



Id have to agree... It's like punching two guys in the face... One may pile up on the ground--the other may just stand there.

The trees could have easily reacted differently to the Roundup, especially with varying degrees of root depth, Roundup % sprayed at each section, etc.


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## vmachnig

Why would it have just done so now, it has been basically a year since I had applied it and it has been fine and by appearances very healthy up untill about two weeks ago when it just dropped all of its needles.


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## Metals406

vmachnig said:


> Why would it have just done so now, it has been basically a year since I had applied it and it has been fine and by appearances very healthy up untill about two weeks ago when it just dropped all of its needles.



The seasons could effect the species... Coming out of winter etc. If you sprayed before winter last year, the tree is a lot more dormant in winter... Come springtime, it starts doing it's thing.

Or it could be a problem completely unrelated to Roundup? :dunno:


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## Urban Forester

Given that only one or two are showing sypmtoms I would GUESS that this is a case of an ornamental hemlock with an undersized root ball at time of planting that has not developed a vigorous root system. The spoadic nature of the dieback is more consistent with a slowly failing root system than with the systemic nature of round up. Due to the rather immobile nature of roundup in the soil, had enough roundup been applied to cause root death the damage would also be on either side of the affected shrub. Also the fact they are in full sun is not ideal and irrigation should be regular to avoid further stress.


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## S Mc

Another thought is have you used any weed and feed products on your lawn? The chemicals in these products, such as dicamba, can also build up and have negative impact on nontarget plants. 

I'm curious as to the multi-trunk comments. This species should be single trunk. So am wondering what the quality/condition of the plants were at purchase. Compromised root systems or other genetic issues may become obvious only later on as the tree tries to develop (as pointed out by Urban Forester).

The full sun shouldn't have been an issue as long as the site was well-drained without strong, drying winds to contend with (Dirr, pg 1031). They also like organic matter in the soil.

Sylvia


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## arbadacarba

Hemlocks naturally are a nurse tree. I would agree that putting roundup anywhere near a tree is not a good idea, but what you might have is natural thinning caused by fungal transfer. If you find a young stand of natural hemlock you will find a great number of trees that look exactly like your pictures with no interference from people whatsoever. One year after death the root structure decays to the point where you can pull a two to three inch trunk out of the ground with one hand. You don't find this with most of our other species as their natural spacing and hardiness is far better. For this reason , among others, hemlocks are far better as specimen trees than as hedges.


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## PB

arbadacarba said:


> Hemlocks naturally are a nurse tree. I would agree that putting roundup anywhere near a tree is not a good idea, but what you might have is natural thinning caused by fungal transfer. If you find a young stand of natural hemlock you will find a great number of trees that look exactly like your pictures with no interference from people whatsoever. One year after death the root structure decays to the point where you can pull a two to three inch trunk out of the ground with one hand. You don't find this with most of our other species as their natural spacing and hardiness is far better. For this reason , among others, hemlocks are far better as specimen trees than as hedges.



I can only speak from my experience but we don't have a lot of fungal problems with the Hemlocks here. They are a different species here on the east coast. Maybe someone could give more insight.


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## S Mc

Arbadacarba, your comments about hemlocks being nurse trees bares out the observation of over competition. I would say that if the homeowner dug these trees in a natural forest situation where some of the trees had survived to this point in a multi-trunk situation, that they may be selectively thinning themselves.

If purchased from a nursery situation, perhaps wholesale or state nursery, then these may have been planted multi-seed to a bag and, again, are selectively thinning.

A possibility.

Sylvia


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## Urban Forester

The "multi-stem" nature of these paticular hemlocks is very common, at least in Michigan. I've seen hundreds, if not a couple thousand. That's why I use the term 'ornamental' hemlock. People buy them and SHEAR them into cone-shaped shrubs (don't get me started on that) How they are 'created' I have no idea. Native hemlocks ARE single trunk trees that can put out a rather impressive root system, these simply do not. I have seen numerous cases (in the range of 30%) where after planting (5 to 7 years) excavation revealed that the root system did not extend even to the dripline. They have a nasty habit of becoming root-bound, The bio-mass of feeder roots that are viable could not support a taxus 1/3 the size. I don't know if it's genetic or simply undersized at point of sale, I just know they have a VERY weak root system and require a lot of TLC to get the roots established. Due to NOT being able to establish good roots these "ornamental types" go into heat stress VERY easily when planted in full sun, as their roots can't draw enough water to protect the needles from scorch. Those pictures seem to show what I've seen in many of these "ornamental type" Hemlocks.


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## S Mc

UF, super interesting information there. We were discussing nursery practices recently here with starting seedlings/liners/saplings using the planting bags. The recommendation was to plant at least 2, sometimes 3 to a bag; the rationale being that alone they did not survive but with multiple seedlings to a bag the success ratio was much greater.

Your "ornamental hemlocks" sound suspiciously as if the nursery practices there are using this theory. That would be interesting to know. Unfortunately, this does not bode well for the OP. Do the surviving hemlocks do ok? Or are they also permanently root-deficient in your experience?

Sylvia


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## vmachnig

S Mc said:


> UF, super interesting information there. We were discussing nursery practices recently here with starting seedlings/liners/saplings using the planting bags. The recommendation was to plant at least 2, sometimes 3 to a bag; the rationale being that alone they did not survive but with multiple seedlings to a bag the success ratio was much greater.
> 
> Your "ornamental hemlocks" sound suspiciously as if the nursery practices there are using this theory. That would be interesting to know. Unfortunately, this does not bode well for the OP. Do the surviving hemlocks do ok? Or are they also permanently root-deficient in your experience?
> 
> Sylvia



The rest of the trees are doing very well as you can see in the pictures, including the other trunks of this particular tree. When ever this happens it is very sudden, the tree looks fine up until the point it starts to shead its needles. As I said in a couple of cases I have seemed to have caught them early enough and brought them back before thet are competely absent of needles. I don't know what it is that I did though to rescue them. Once the have shead all of their neddles though they are dead.


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## Urban Forester

S Mc said:


> Do the surviving hemlocks do ok? Or are they also permanently root-deficient in your experience?
> Sylvia



They do survive, although I have noted 2 interesting issues. 1) The color is almost chlorotic, but not distinctly chlorosis. In other words pale I guess would be the best description. Regardles of treatment, i.e. iron, sulfur, etc. they never get to "hemlock green". 2) The other thing I've seen alot is a multiple center leader that ends up intertwining around itself. This leader then thins and will not retain needles. In fact I was on a property today where a 5 footer had both color issues and multiple leaders. Close inspection showed ONE strong trunk until about 2.5 ft from the top then it split into 3 distinct upright central leaders, planting was good, mulching perfect. It had been in the ground 5 years, was only 5 feet tall, but 6 feet wide, not uncommon, interior needle loss was dramatic, color poor (in my opinion) and excavation revealed no viable roots more than 3 feet from trunk. These things are genetic freaks, or Sylvia, you may be right, it may be a nursery thing. I don't know, but I would sure like to...


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## S Mc

Vmachnig, do you have any single trunk specimens at all? And if so, have any of them died? Can you do a bit of forensics here and check to see if the ones with multiple leaders are in fact multiple stems from a single trunk or multiple (cluster) trees intertwined?

You state that you have not seen any pests but used insecticide anyway. Please do not do that. You are killing any beneficials that might be around and upsetting a natural balance that is necessary to maintain a healthy landscape.

I really don't think this looks like herbicide damage in the fact that I believe you would see a different pattern to the die back rather than selective, as pointed out by Urban Forester. But I encourage you to minimize use of that product as well. Maintaining a moderately thick, constantly decomposing mulch layer in conjunction with proper irrigation are the two best cultural practices you can do for any tree.

If this is a natural dieback from the overcrowded situation, the remaining trees may be fine and in fact better in the long run. 

Sylvia


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