Hello, I need some help from your experienced team.
I’ve a row of Cedar trees at my home. The trees are now at least 12-14 feet tall, and it’s been 7 years since I got them planted. For the past three years, the trees from left started getting some issue and started tuning brown and died. It’s leaf would go hanging down as if there is no energy left in it and eventually turning brown and then dead. It would take good 5-6 months for it to die. Then the next tree got similar behavior and eventually it died too. Then the third tree in sequence died. I got them replaced and changed the soil too while replacing the trees. After replacing these trees, the next one (4th tree in row) which was there, it started showing the same pattern and then it died. Then the 5th one died and so on. Every time, I replace the dead ones, the good tree in sequence (say 6th tree in line) starts showing the behavior which was good before replacing. So far I’ve got 10 trees replaced and I can see the next two trees are showing the same behavior and I was wondering if your team can do a diagnostic on my trees and let me know what exactly is going on as I’ve a row of 48 trees and I’m freaking out even thinking about if they all will die one after another.
Surroundings on my side:
I used to have soaker tube before for watering then I asked for an arborist to come and check. He didn’t find any insects, he suggested to have good watering system and I put in a sprinkler system. Every time the gardener came to replace the dead trees, they didn’t find over/under watering, root system was well developed and didn’t find any stress or sign of underdevelopment of roots. I’ve used fertilizers sticks only 2 times so far and that too like 3-4 feet away from the trunk. I do use mulch around the trees to keep the moisture around there. There is plenty of sunshine during the day in my yard as it’s a big yard and very open.
Thanks very much for your help!
Thank you for contacting the Toronto Master Gardeners.
Also, for taking the time to research the literature and consult with a certified arborist and gardener about your dying Emerald Cedar hedge. As you are likely aware, Cedar hedges are not easy, so it is possible that we will not be able to help you prevent further deaths. However, based on what you have said (no pests, enough sun and water, infrequent fertilizing), here are a few newish ideas you may not have considered.
First, you may benefit from reading this depth the UBC article, which is one of the best available, on understanding the issues faced when growing an Emerald Cedar hedge. UBCcedar. It contains a photo of Keithia blight a common fungus infection. Please look at your older trees to see if you can find anything resembling this fungus. If so, you will need to have a registered professional apply a fungicide to all your trees.
Second, as the deaths are progressive from the left to right in your pictures, are you sure the drainage and sun are not different from one end of the hedge to the other?
Third, have you determined whether or not the roots of your dead trees were girdled (also explained in the UBC article). Consider digging up one of your older live trees (the next in line to go), and examine the roots. Make a large and deep divot around the tree roots without harming the neighbouring trees when doing this. After 7 years, all shape of the original pot or burlap ball should be absent and you should see new whitish roots, extending outwards and downwards, growing off bigger roots. The original roots should not be making circles and the root ball should be a combination of your garden soil with remnants of the original nursery soil.
Also, look at the bottom of the hole. Is it wet (slightly damp is good, waterlogged is not)? Is it solid clay? Does it smell swampy? If yes to any of these, you may consider removing all the trees, teasing out the roots, digging a new deeper trench, and adding good quality triple mix before re-planting the trees. Adding a few handfuls of superphosphate fertilizer at that time will help root growth.
Because cedars prefer a basic soil pH, you many want to add a few handfuls of lime, either on the top of the soil or worked into the soil if you choose to replace it. pH. If you feel you must replant all 48 trees, consider hiring a reputable landscaper to help.
Finally, if none of the above ideas appear relevant, it might be a good idea to remove and discard all the existing mulch in case it is harboring pests or diseases. Replace this by topdressing with 3-4 inches of good quality well rotted manure along with some slow acting chemical fertilizer formulated for evergreens. Once this is done you can re-mulch with fresh store-bought bagged wood chips for the winter (do not bring any organic matter right up against the tree trunks).
In the spring, reapply manure and/or compost and a small amount of high nitrogen fertilizer, (smallest amount recommended on label), and hope that good nutrition will improve the plants’ immune systems.
Of note, could there be something happening on the other side of the garden fence that could be impacting your trees? It might be worth a look or a chat with your neighbour.
Hope this information is helpful. Good luck.