Answer: Arborvitaes are usually hardy plants and once they become established will grow and thrive without a lot of care. They need well draining soils and a deep watering once each week. I suspect that you have over-fertilized your plants. Too much nitrogen will burn the roots, which will show up as brown foliage. Fertilizer spikes are slow release and a steady amount of fertilizer will translocate to the roots. The spikes are designed to last a full year. If you fed your plants in the spring and then again in the fall of the same year you effectively doubled the dose of fertilizer which may have been enough to burn the roots of your plants. I'd remove any remaining fertilizer spikes and flood the soil to help leach out excessive salts. Then water your arborvitaes deeply once each week throughout the growing season. When you begin to see new growth emerging you can prune away the damaged foliage and stems. With any luck at all your plants will recover. Hope so!
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