I planted Arborvitae and they turn brown. I purchased them from Home Depot and had to return them twice. I love the look and enjoy the privacy and would like to plant them again however my neighbor in the yard behind me has an old walnut tree and I’m told that is the reason my Arborvitae will not grow. Can you please share information as whether this is true or not? Thank you for your help!
Yes it's possible that black walnut is at least partially responsible for the decline of the arborvitae, especially if the walnut canopy is overhanging the area where you are planting the evergreens, and if the root system of the walnut tree dominates the area of your plantings. Competition for sunlight is a big factor, competition for water and nutrients in the soil is another. And black walnut is known to have chemical properties that create a condition called alelopathy, that suppresses growth of some underlying plants.
But decline and mortality of newly planted arborvitae is more likely due to other factors. Good growing conditions, soil and water management are essential. Handling and planting technique, plus adequate watering of new plantings are primary considerations.