Thanks for your email. It’s difficult to tell from your photos where your periwinkles are and what sort of weeds you have. I can see some Mulberry weeds in the photo, but I also see some grass (grassy weeds?) in the foreground. I don’t see periwinkles.

Basically, there are two kinds of weeds—broadleaf (e.g., Mulberry weeds) and grassy weeds (e.g., crab grass). A broadleaf weed killer will kill broadleaf weeds and there are many. On the label, you will always see as one of the ingredients 2,4-D. However, periwinkles are a broadleaf plant and 2,4-D will kill them as well.

Grassy weeds can be killed by a glyphosate product such as RoundUp. However, glyphosate kills broadleaf weeds and is harmful to most plants, flowers, etc. I cannot tell from your photo where the periwinkles are in relation to the weeds. Are they intermingled? If they are separated, then you could cover the periwinkles and spray the weeds to kill them.

Hope this information helps,
Rick Williams