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Emerald Green Arborvitae

Greetings from Lowell, NC! My question(s) relate to treating several possibly-over-watered Emerald Green Arborvitae. Hopefully the information I provide will be relevant.

I planted 22 of the trees in mid-June. All were 3-to-4 feet tall and in 12" and 13" pots. The great majority of the trees are planted on a short hillside with a few trees on mostly-flat ground at the top and bottom of the hill. I installed drip irrigation at the same time and all have been watered regularly and consistently. Everything was going great until a couple weeks ago ...

Five of the trees began to appear as though they were under-watered (yellowish/brown appearance and looking dry), and of course my reaction then was to increase watering time. The appearance has only degraded a bit. Much of what I've read since suggests a tree that has been over-watered, and may be suffering from root rot, can take on the same appearance. Yesterday I dug down beside a couple root balls to inspect. The surrounding soil (clay) was consistently moist but I couldn't really decide on the soil of the root ball. The root ball certainly wasn't sopping wet but I couldn't squeeze that soil into a ball in my hand either. Today I purchased a moisture meter and the root balls of all trees in concern are registering wet, wet, wet. All of the trees that look good are registering on the low moist side.

I mentioned there was a hillside involved. What I think may be happening is the root balls on the hillside are receiving sufficient water but I know much of the water is running off the hill. On the other hand, the trees that are on flatter ground are receiving much more water to the root ball - maybe too much. It has been very hot and very dry in these parts, so suffice it to say the ground is very hard and the trees are basically sitting in hard clay pots in the ground without a great ability to drain. I'll answer any question about the initial planting but let's assume for now they were planted with great care, with sufficiently sized holes, and with nice soil conditioner.

So, how can I verify with any more certainty my trees are under-or-over watered? And is there a way for certain to verify if 'root rot' is at play? And if so, what can one do about it? I'm inclined to dig the trees up, re-pot them, dry up the root ball a bit, and replant the trees after a while. Hopefully that's an absolute last resort.

Looking forward to any ideas you may have!


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