Answer: Even if you tear it out the quackgrass will probably come back so that is not going to solve the problem. Usually, an established mature planting of vinca is thick enough to choke out all weeds including grasses, so it may be that in a few years yours will be able to do that naturally if you can be patient. In the meantime you can continue digging and pulling it to make it look better but I realize this is a huge job. You might want to discuss other chemical control measures with your local county extension. They will have the most up to date information as to what can be used with vinca and what is registered for use in your state. Good luck with your planting!
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