We have a Vinca minor problem. Two years ago a black patch developed in a luxurious patch in the rear of our house. It spread until nearly all the Vinca died. Now a patch has appeared in the front of our house in a 'Bowles' variety planting. It too is spreading. I'm at a loss to explain what's happening let alone to find a way to cure the problem. There doesn't appear to be any insect problems nor mildew or other signs. The plants just die and turn black. The soil is heavy clay, but the Vinca has grown here for at least 20 years and spread over large areas. Any help or suggestions will be appreciated. Ray Stilwell
