For a healthy looking periwinkle, make sure you eliminate every trace of moss
Q: We have moss growing in a patch of periwinkle (Vinca minor) and we wonder if there is anything we can spray or dust on the moss to kill it. We have dug most of it out but would like to eliminate new growth. Thank you. – Jean Howe
Moss tends to flourish wherever there is poor drainage, shade, acidic soil and a lack of fertility. Correcting or altering these conditions should hopefully decrease the amount of moss and/or improve the growth of your periwinkle, which will in turn smother future moss growth. The existing moss can be physically removed. I don’t recommend the use of a contact spray around your periwinkle, e.g., Safer’s De-Moss, as this could potentially damage existing foliage. If you do want to use a spray, I suggest a possible scenario in early spring, before new growth occurs on the periwinkle: 1. Cut the periwinkle back to ground level. 2. Spray the exposed ground to kill whatever moss is present. Note: Safer’s De-Moss works better under dry and warmer conditions; always read instructions before using. 3. Lime and topdress the bed with a thin (5-cm/2-in.) layer of compost. 4. Apply a general fertilizer, as directed on the package, about 14 days later to promote new growth on the vinca. Avoid applying lime and fertilizer too close together.