My arborvitaes are dying and I am not sure what to do.

Asked June 10, 2020, 3:10 PM EDT

Hi, Some History: * Last year: I planted 20 small American Pillar Arborvitaes on 5/8/2019 in my backyard in Apple Valley. I kept them watered and just before the winter they all seemed to be doing ok. Some had grown taller than others, but they were all alive and healthy looking. * This year: This spring, around 5/4, I noticed several were yellowing. A couple weeks later one of them was completely stiff and white. Many of the others showed partial browning in areas. Over the next month 2 more died, and now there are 2 that are beginning to look like the others that died did before they died. * What I have tried: I consulted an arborist I found online, the most expert person at bachmans when I went there over a month ago, and the Apple Valley forestry service person. Bachmans suggested fertilizer stakes and Iron Sulfate, which I tried a little bit but not extensively (to be safe) and to check the soil PH, which was 6.75. The arborist was no help and too busy to come out. The city forestry person didn't know why they had died, recommended to continue watering them, stop using chemicals on them, and trust that they are doing their best, which was comforting but not particularly helpful. The place I bought them from said to only water the first year after they had been planted, so until the suggestion to keep watering them was made on 5/13, I hadn't watered them myself in 2020. That might have been related to them dying, but wouldn't explain why there is continued death. I looked at the information on this site too and nothing quite seemed to fit as far as I could tell. Current and Future: I have 8 new trees from the company in South Carolina that I bought them from (warranty) but I am not sure how best to proceed. I want to understand why they are dying, and what I can do to stop it, and also what I need to do to make sure the new ones I plant don't also die. They are planted in a single row and will form a privacy screen when grown, so if even one dies the whole screen is compromised. I am including a few images of tree #5 which is the most concerning of the still mostly alive trees, I am also including a rough possible plan for the 8 new trees, but I don't like that the hedge won't be a straight line anymore. Here are some quick videos I made summarizing their state: 5/26 https://youtu.be/wTsKtw3qIPM 6/10 https://youtu.be/UQQhBgPz6k8 Why are they dying? What can I do to help prevent any more from dying? What is the best plan for the 8 new trees? Thanks in advance, Aaron

Dakota County Minnesota

3 Responses

I can speculate that they are dying from transplant shock and lack of water. The soil should be kept moist but not wet. They will need water every time the soil dries out to a depth of 2 inches. They could also be suffering from sun scald. They are very small trees. The trees you are buying are also adapted to a warmer climate. It is always better to buy trees that were grown in a similar climate to the one where they will be planted. It can take several years for trees to acclimate to a new climate and not all can in time. A staggered line will be best in the long term. The trees will spread as they go and unless you are willing to wait years for the branches to touch they will be too close together when they are mature and shade each other’s branches out making the screen sparse.

I am sorry, I find it very frustrating when trees especially don’t thrive after the effort and expense to plant them.
https://hort.extension.wisc.edu/articles/winter-burn/

Evelyn,


Thank you so much for your reply. Given my observations, and the locations of the trees that died, this explanation seems the most plausible. I will take greater precautions this winter.

I had a few follow up questions.
  1. Ive read that too much mulch around the base of these trees can trap water and damage the tree and kill it. That is why i only put an inch of mulch down last autumn, one bag for all the trees. The info sheet you shared said to keep it three inches from the base, so it sounds like I should add a bed of 3-4 inches deep of mulch around all of the trees and make a little ‘hole’ in the mulch around the base of each tree. Are there any ring products I might use to keep the mulch from falling back in and up against the tree trunk? Should I remove the mulch in the spring/summer? If I’m testing soil moisture I assume the mulch is then not part of the “soil”?
  2. Tree distance. The site I purchased them from said they would grow up to 30’ tall and up to 4’ wide. When I planted these last year I had scoured the Internet for information about how far apart they need to be planted. I got answers ranging from 2’-5‘. I went with 3 feet where I wanted the most screening. I figured they would overtake each other and some of the insides would die off due to being shaded by other branches but decided that was just how it had to be for a screen hedge. Your reply suggested that eventually being this close together would result in them eventually dying as they grew together. Is that correct? If I do need to separate them do you recommend that I try and move some of them so they are more staggered? What distance do you recommend I separate each tree by?
  3. It sounds like these need a lot more water than I gave them. When I first planted them, I started watering them a lot but started to worry I was overwatering. What is too much, and how will I know?
  4. Regarding snow fencing. Can I apply this barrier around multiple trees or does each one get its own? Should I try to shovel the trees out if they get covered in snow?

Thanks again. I really appreciate your help with this. I very much want these trees to thrive, and give them whatever they need to best do that.

-Aaron

1. Mulch under trees should not be deeper than 2 inches. Trees need oxygen. Keep pulling the mulch off the trunks.

2. At 3 ft apart they will shed out side and bottom branches and likely survive.
3. Test the dirt not the mulch. If it’s dry to 2 inches it needs water.
4. Snow fencing can be set up around multiple trees. Snow cover insulates trees and protects them from winter burn.

Good luck with your trees.