My Green Giant Arborvitae Is Turning Yellow

Kinds of Arborvitae

• In addition to the fact that arborvitae shrubs are easy to grow and relatively cheap, there are a number of differing species to choose from based on height and color. One of the tallest and most imposing is the Nigra. It can reach up to 40 feet tall and has dark green foliage. One of the more common arborvitae chosen by homeowners is the emerald green arborvitae. It is smaller, usually around 15 feet tall and sporting bright green foliage, as the name implies. Others include the green giant, which is slightly smaller than the nigra, which is around 30 feet, and the Hetz midget, which barely breaks 4 feet. Yellowing of any of these green arborvitae is a sign that something is wrong.

Growing Conditions

• Arborvitae prefer well-drained soil with a little moisture. Since they are generally grown for display, growing them in sunlight or only partial shade is necessary. When they are grown in full shade, the shape is compromised because the weakened stems cannot support the foliage. The foliage may yellow and fall off. Soil should drain well to help prevent fungi that could also damage or weaken leaves.

Phompis Blight

• Phompis blight is a fungal disease known to directly attackarborvitae. The fungus that causes the disease is Phomopsis Juniperovora, which also targets junipers and other shrubs. The disease causes the plant to deteriorate, its foliage changing from green to yellow to eventually a reddish-brown color. To control the disease, cut off any parts of the plant that start to yellow. Only plant those cultivars known to resist the fungus.

Fletcher Scale

• The fletcher scale is an insect that attacks both junipers and arborvitae. They are a tan to brownish color, circular shaped and around 2 to 4 mm in diameter. Not only do they extract fluids from the plant, weakening it, but they also exude a substance called honeydew, which disrupts the plant. The honeydew causes yellowing foliage, and eventually the needles fall off. To control fletcher scale, an insecticide containing acephate should be used during summer.