Emerald Green Arborvitaes - Inner Leaves Turning Brown in late July normal?

Factual Questions
1

Hello,

I recently planted eight 12 foot arborvitaes in my yard as the start of what will be a privacy screen between myself and the neighboring homes. My plan is to add an additional eight next year. Actually, I would have gone ahead and planted all 16 at once if they weren’t so expensive! It cost me $1,100 for all these trees and that’s a pretty penny where I’m from! (Northeastern PA)

So these trees have been here about 3 weeks now and I have watered them a few times. Probably once or twice a week at most. My first week I probably overdid it a little bit, but I have been trying to not be so obsessive about it as I know over watering can be fatal for these trees as well. Unfortunately, I read that you should water these trees even if it is going to rain since the roots will not absorb as much rainwater as they require. What that means is that I have been checking the soil, and even if the forecast called for some rain, or even a lot of rain, I figured I should give them a little drink anyway just to ensure that the roots were able to get what they needed just in case the rain didn’t provide enough water deep enough to benefit the trees.

With the current weather here in my area being a good ten days of heavy rain, I am very concerned about the roots being drowned in all that moisture. It also doesn’t help that I gave them all a drink on the morning of the day when all of this heavy rain began . . .

Obviously I won’t be watering them again for awhile as we still have a few more days of heavy rain on the horizon . . . Probably won’t even give that a second thought again until at least early August.

But I have noticed that the trees are all getting very, very brown on the inside of the trees, and there is some minor browning on the outer part of the trees as well. The trees appear mostly green on the outside, but I am worried because of all the rain and because I am new to this sort of thing that the trees are severely over watered and possibly dying.

My plan, assuming these trees aren’t dying, is to cut back to one watering a week (while continuing to check the soil to see if it is required or if an additional watering may be needed).

I have read that evergreens normally turn brown in late summer . . . but it’s not even August yet so I simply must ask: is it normal for arbs to show this sort of browning this time of year?

Is this more common for trees that were recently transplanted?

Or have I quite possibly killed my trees by trying too hard to keep them watered?

Any advice is appreciated, and thank you in advance!

2

Have you looked at the leaves to see if there is any tree pest infecting them?

3

I have been looking but I don’t see any pests or anything living off of the trees. My best guess as to the browning of my trees is that all the hard rain we’ve been getting combined with my inexperienced watering thus far is killing them . . . OR maybe the trees are simply doing what evergreens do and shedding their inner leaves? I have no idea because it seems pretty early in the season for that, but I have read that transplanting arbs can cause them to brown and shed their inner leaves early.

I am really hoping that this is just normal for these trees and that I am not to blame for their browning, because that would just be awful after all the work and expense I put in getting them here.

The trees appear to still be alive and because we are still in the middle of some pretty wet weather for at least another week I was considering putting down some sort of temporary plastic barrier over the soil around the trunk to prevent any additional water from working its way down to the root ball and further drowning out the roots (assuming that is the problem) but I am not sure if that would help or make things worse by potentially trapping moisture in the soil. Anyone have any tips on how to protect/revive arbs that are getting drowned out by hard rains? Is my idea a good one or not so much?

ANY advice is appreciated as I am a total newbie to planting and maintaining trees and I just wanna keep these poor trees alive!

Thanks for reading!

4

I have one arborvitae (for around 15 years) and it has always been green only on the leaf parts exposed to sunlight and brown deep inside, so if it is a problem I have it, too.

5

Hmm, perhaps I am making a big deal out of nothing. I have never had arborvitaes before so it could be that they are just like that and that there is nothing wrong at all. I hope that’s the case! Right now I am just keeping an eye on the arbs to see if they continue browning on the outer branches. Thanks for providing some perspective!

6

The only way to know if the soil is too damp/soggy is to dig down at least a few inches in the planting area to check. A combination of heavy rains and poorly draining soil could well mean the trees are waterlogged and need a break. Don’t cover the surrounding soil with plastic, as it’s not going to help (moisture will seep in from elsewhere) and could hurt by trapping water in the soil.

I have a long row of "Green Giant’ arborvitae as a screen, and I’ve never noticed inner browning during part of the year. They’re in average soil, I gave them supplemental water as needed during their first couple of years, and now they’re upwards of 25 feet tall.

7

Here’s a related question. I’ve had some Nigra arborvitaes for the past 10 years or so and they are doing very unevenly. Some have grown tremendously and are full of green, and others have only grown a bit and have thinned significantly. It’s unclear to me what the difference is between the various shrubs. But in any event, what happens is that in Autumn there’s significant drying up of many leaves, and the weaker shrubs dry up a lot more than others. So I’m wondering if there’s some sort of water issue. (Or could possibly be related to roots of trees in the vicinity?)

My specific question is like this. When leaves come off the trees in Autumn, they tend to congregate at the roots of these shrubs. It would require a bit of extra effort to dig them out and clear the base of leaves, and I never really bothered to do this. The reason is that I’ve read that these shrubs need acid, and I figure decaying leaves would provide some of that. But now I’m wondering how that impacts the water situation. On the one hand, it might mean that less water gets to the roots. OTOH, it might mean that what water gets through doesn’t evaporate as quickly. So I’m unsure what the smarter approach is.

8

Check with your county extension office. They should be able to find someone who is qualified to give you specific advice for your trees in your specific area. It’s what they do.

9

I’ve seen this happen after transplanting large arborvitaes. I,m not sure why but it’s common in transplanting bushes of similar size. Just guessing but it may result from root damage or excess time out of the ground. These are slow growing plants and should eventually recover but it may take some time.