Question: My periwinkles are drying up one branch or plant at a time. What can I do to help them?
Answer: That's a soil-borne water mold fungus called Phytophora. Unfortunately, we do not have an effective chemical control for it. Most commercial landscapers and nurserymen advise against planting periwinkles, particularly if this disease has been a problem. Consider planting in containers away from your native soil, and wait until summer to plant, once the splashing spring rains are behind you. Drip irrigation lessens the chance of the disease attacking the plants.