Browning Emerald Cedar


Hi team,

I hope this finds you well! 1 and a half month ago, I transplanted three 6ft Emerald Cedars. I dug up a large root ball and planted them using 60% native soil, 40% topcoat/compost. They were thriving for a few weeks, looking lush. Now, two of the three are browning. I have ensured they are watered thoroughly. They receive about 4hrs of direct sun, and the rest indirect sun. I did have to sever some large existing tree roots (maple and cedar) of large trees I had taken down that are close to where I planted the new emerald cedars. I am wondering if the severed roots are leaking into the soil and impacting the new growth? Also please note about 1 and a half feet down, it is clay. One of the three cedars which is located in the background of the 2nd photo is doing very well.

This is the second time I have transplanted cedars to these locations, and they died last year as well. Any thoughts are greatly appreciated? Do you think I can save them? Perhaps I should add some fertilizer?

Photo: Emerald Cedar, 6ft hight, 2-3 ft spread, sun/shade, moist soil, clay about 1.5feet down. There is some moss growing near one of the cedars lots of rain and I have been watering a lot).

I have read many of your existing forums on Emerald Cedars, but wanted to message and ask regardless.

Thank you so much!!

Emerald Cedars, or Thuja Occidentals ‘Emerald’, should be transplanted as early in spring as possible- which you’ve done.
They prefer fertile, well draining soil. They love consistent moisture, but do not like to be in waterlogged soils. You noted that you have clay 1.5 ft below ground level. It is possible that your soil doesn’t drain freely. The moss you mentioned growing on the soil surface is also a sign that your soil could be draining poorly.
When you water the trees the soil may appear to drain well, but the water may be draining well through the sandy loam topsoil until the water reaches the clay layer below. This could have a bath tub effect, trapping water at the base of your cedars root ball. Is it possible that the one tree that is doing well is on slightly higher ground? It maybe out of the clay soil area. It looks like it may also be away from the trees that were cut down.
Roots require oxygen to grow. The oxygen is trapped in the spaces between the soil particles. If the soil is waterlogged, then water can fill the air spaces- effectively suffocating the root ball. This wet environment promotes pathogens, such as fungus, that can cause root rot. Useful micro organisms, that help your trees to take up nutrients, also need oxygen. There are a multitude of reasons why Cedars turn brown, but in this case I think it is likely to be that they are standing in poorly drained soils.
You can test your soil to determine whether it is draining adequately. See link below. According to Landscape Ontario, planting trees in poor draining soil is possible with a few modifications.
1. Find the root flare on your tree.
2. Remove excess soil covering the root flare and loosen soil at the bottom of root ball.
3. Measure the distance from the top of the root flare- where the roots flare out from the trunk, to the base of the root ball.
4. Dig a hole three times the width of the root ball diameter at the soil surface. Dig it to a depth that is 7.5-10cm less than the vertical root ball measurement you made.
5. Loosen the soil around the planting hole 1-2 feet (30 to 60 cm) outward using a shovel. Take care not to dig deeper than the root ball depth.
6. Place the tree in the hole so that the root ball sits at the base of the hole and the flare is 7.5-10cm above ground level.
7. Backfill the hole as per the detailed instructions on the link below.
Here is the link from Landscape Ontario that has instructions on how to do the soil drainage test (on fact sheet 2), as well as detailed planting information for poorly drained soils- on fact sheet 6. Landscape Ontario Link
Emerald cedars prefer full sun, but can tolerate part shade. The location you describe sounds like it may not be sunny enough. Part shade is equivalent to an average of 5 hours of indirect sunlight per day. If your trees are getting 4 hours of full sun per day, then they are likely getting closer to 10-12 hrs of part shade during the summer months.

It is possible to keep your trees alive with lower light levels, but the canopy is likely to become sparse and less vibrant green. The dense, rich green foliage that Emerald cedars are known for rely on as much full sunlight as possible- preferably all day.

I can see that you have planted your trees nears the stumps of other trees. It is difficult to tell if the stumps are alive. If they were recently cut down, and the root balls are still intact, they could continue to grow and eventually become competition for space, nutrients, light for your newly transplanted trees. Currently, any remaining roots from your chopped down trees could be obstructing or restricting the roots of your new cedars. Do your cedars have the recommended 2 ft of clear soil around them?
When larger trees like your cedars are transplanted, it’s best to make life as easy as possible for them. They need space for their roots to grow freely, in a spot with ideal growing conditions. If you have dug around in your yard you probably have an idea of how extensive the clay soils are. If the clay occurs in patches, it could be possible to revive your trees by following the landscape Ontario planting guidelines. If you have planted the trees too deeply, and your soil drainage test results are poor,  the best option is to replant your trees in the fall when they are dormant.
While you are waiting for dormancy, reduce your watering routine. Check the trees every 4-5 days. Put you fingers into the soil. Water if the top 2 inches of soil is dry.  Adding 1-2 inches of organic compost as a top dressing around your trees with provide some slow release nutrients. Mulch is also great for keeping the soil moisture levels consistent around the tree. Pull the compost and mulch 6 inches away from the tree trunk to prevent moisture being trapped against the bark, which can cause rot.
You may find that your trees respond well to less frequent water, and the added nutrients and mulch. If your trees improve, you may decide to leave them where they are. Good luck!