Vinca minor, aka periwinkle, is listed on the Fertilome Over the Top II Grass Killer product label as tolerable to the product.
Fertilome Over the Top II is one of the most popular herbicides to kill grasses such as Johnsongrass around landscape ornamentals. We are not sure if it would behave differently in xeriscaping or not, just be sure to check the product label to be sure that your plants will be tolerant to it. Be sure to use a surfactant such as Hi-Yield Spreader Sticker with Over the Top II.
Yes, Fertilome Over the Top II can be used over cactus/suculents.
You can buy Feritlome Over the Top II Grass Killer on our website or you may contact our facility at 1-866-581-7378 for further assistance.