herbicide ithat will not kill periwinkle
What herbicide is available that will not kill periwinkle? I want to establish periwinkle as a ground cover but weeds and grasses overwhelm the periwinkle.
You pretty much have two choices which are to pull the weeds by hand or carefully paint, with a small artist paintbrush, the foliage of the weeds with a herbicide such as glyphosate, being careful not to touch the periwinkle. You should also put a few inches of mulch around your periwinkle to suppress unwanted weeds.