While we do not recommend Vinca minor/major as a groundcover in our area due to its aggressive invasive tendencies (it has escaped cultivation and colonized parks and other wild lands, out-competing native wildflowers), a pre-emergent might help provide control of warm-season weeds if applied in spring. Cool-season weeds, growing now, are best controlled in autumn, when they first sprout. We do not have specific brand recommendations, but you can look for products that list Vinca as tolerant of its application, as well as which lists the specific weeds in question on its label as those it controls well. If you need help in identifying which weeds you have, you are welcome to send us photos. It is possible that grassy weeds and broadleaf weeds will not be controlled equally well by the same treatment, as they often metabolize herbicides differently and have different sensitivities. Temperature and moisture conditions will affect the herbicide's performance, so follow label directions regarding how and when to apply. Though this page is directed towards lawn weed control, it may provide some further useful information: https://extension.umd.edu/hgic/topics/lawn-herbicides

As you are probably already aware, pre-emergent herbicides only impact weeds germinating from seed, so for those already growing/mature - especially perennials - hand removal may be the most effective and practical, since the Vinca could easily be damaged by post-emergent and systemic treatments. If Vinca hasn't yet established in the location of the worst weed infestation, simple smothering may be the lowest-impact method for regaining the upper hand; you could use a thick layer of wood chip mulch or landscape fabric (which should be removed upon planting).

If you are open to it, consider using an alternative groundcover, particularly as a mixture of species. Natives may be better-suited to the site conditions and should be of better benefit to pollinators and other wildlife. Whether native or not, a mixture will have better resiliency in the face of weather, pest outbreaks, disease, and other stress factors. Here is a sample list of some popular options: https://extension.umd.edu/hgic/topics/groundcover-list

Miri

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