Vinca a.k.a. Periwinkle is one the best summer flowers you can grow when planted at the right time and with a few extra steps to insure success. First, wait for longer & drier days to plant. They do not like wet conditions which leads to Phytophthora Stem Blight and Root Rot Fungus. Water management is the main preventative measure. It is important to provide excellent drainage and full sun.When preparing a planting bed be sure to work in plenty of organic matter such as Cotton Burr Compost. Treat the area with Actinovate or Actino-Iron, a biological fungicide to help prevent disease. Space the plants 8-10 inches apart since air circulation is key and mulch heavily with Hardwood Mulch to prevent water from splattering off the soil onto the plants. Always water slow and deep at the base of the plant, never over the top if possible. Once you get these beauties established , they can provide you with easy year round color for several years.