Arborvita shrubs turning brown

Asked October 22, 2014, 1:24 PM EDT

I have 6 shrubs(6ft tall) planted in April from large ,pots, I gave them fertilizer both to the roots and foliage with plenty of water, now they are getting large brown spots,would more fertilizer help?

Clallam County Washington

1 Response

Hello, and thank you for your question.
The short answer is that we don't know what is wrong with your shrubs, so don't fertilize them yet. More fertilizer could actually harm them at this point, so hold off until you learn what is wrong.
The Clallum County Master Gardeners may be able to help you diagnose the problem with your shrubs, and I would recommend contacting them first. Here is a link to more information: http://ext100.wsu.edu/clallam/gardening/mg/plant-clinics/.
The brown spots on your new plants could be one of several different problems. If they are mostly on older parts of the plant, it could be the normal leaf loss that conifers experience at this time of year. If the spots are spread randomly on the plants (top, bottom, sides, tips, inner branches) then it could be caused by a pest of some sort, either disease, insect, or other type of pest. If the spots appeared about the same time, and are on several of the plants, that suggests that something environmental or cultural is the issue.
Something that can happen to these plants, is that they can be planted too deeply in the pot or the ground, and when the roots are too low in the soil, they start to die off. If the roots are dying back, then some of the branches may die as well. If you look at the base of the plant, you should see the trunk start to widen or flare out, right at the soil line. If the trunk goes straight into the ground like a pencil, and has no flare, then it may be planted too deeply. This can cause long-term problems for the shrub.
I would highly recommend talking to an expert about this problem. They will probably ask for a sample of the problem, including the transition between healthy and damaged tissue. If you can provide a picture of the plants as well, this will help them identifiy the problem.
Good luck! I hope they recover and provide you years of benefits!