Answer: Boxwoods can suffer from winter kill and from root rot, (Phytophthora parasitica), a soil borne fungus. The first symptom of root rot is the loss of the dark, shiny green leaf color. Leaves gradually turn a light straw color when plants are grown in the sun or dull green when grown in shade. Symptoms appear on one branch or section of the plant, but gradually other branches are affected until the entire plant declines or dies.
Phytophthora root rot is most likely to occur in poorly drained soils. When the soil is saturated, the fungus penetrates into feeder roots and moves up the roots causing a dark discoloration. The outer cells of rotted roots slough-off easily leaving only the central portion. In advanced cases the bark on the main stem just above the soil may also slough-off. Boxwoods that die should not be replanted with boxwoods since the disease is soil borne. Providing good drainage and optimum growing conditions is the most effective method of treatment.
If your boxwoods died from something other than root rot, you can replant boxwoods in the area after amending the soil with organic matter to ensure it drains well. If your boxwoods died from phytophtora, you probably should choose a different shrub for the area. Best wishes with your landscape.
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