Dwarf periwinkle, which is a vigorous but manageable ground-cover here, is an invasive weed in other regions. Locally, common periwinkle, Vinca major, is the more aggressive sort. It naturalizes in riparian situations and damp parts of unrefined landscapes. Stolons can be difficult to pull completely from the soil. Seed disperses secretively but efficiently.
Periwinkle is almost never available in nurseries nowadays. It tends to infest gardens by sneaking in. Then, the foliage and bloom can be too appealing to eradicate. More plants are easy to divide from established colonies. Growth is tidier if mown at the end of winter. As it regenerates, it gets more relaxed, and finally gets floppy. It looks shabby if trampled.
Periwinkle blooms with sporadic but delightfully clear blue bloom. Individual flowers are about an inch and a half wide. The evergreen leaves are an inch or two long. Wiry stems get a foot or two deep. Cultivars with white or purplish blue bloom were available before
periwinkle naturalized. Periwinkle with foliar variegation still inhabits some old gardens. It is slightly more complaisant.
Tony Tomeo 
beautiful, but invasive here too. Many of my clients ask for it and I tend to discourage them putting in their gardens. Is really nice though as a trailer in containers!
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Is that Vinca Major or Vinca minor? Vinca minor is not invasive here; but I read that it is just as invasive as Vinca major in other regions. It cascades nicely. I happen to like Vinca major in urban regions where it can not get very far if it escapes, but it is relatively shabby compared to Vinca minor. For some landscapes, that unrefined shabbiness can be appealing.
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minor, i use it as cascading “spiller” in containers to control it
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Yes, it seems to be much more complaisant anyway. It seems to me that (in our climate) Vinca minor is more difficult to eradicate from the soil, but does not migrate nearly as aggressively.
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I had periwinkles accidentally move with me from my old house. They love it here and are difficult to get rid of.
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Embarrassingly, I actually planted it in a parkstrip many years ago. It gets mown at the end of winter, so regenerates nicely about Now. It has no place to go if it escapes in that particular neighborhood. I really would not want to introduce it into a region where it is not yet established, and where it could do so.
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I spent a great deal of time last summer, eradicating most of the periwinkle from the iris beds at our rock house property. I wonder if Forrest’s grandmother intentionally planted them and for what purpose? I have not seen them elsewhere on the property.
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Most just migrate in from somewhere else, but somewhere, at some time, they were planted. Old photographs in various places show that much of the old landscaping was composed of what happened to be native to a region. What was not native was limited to what was available. There was a time when periwinkle was available, and actually desirable.
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I have it in a couple spots in the garden. Very tough to remove, but the flowers are nice. I’m pretty sure it is still sold here in garden centers. I haven’t tried to eliminate it as we are far from any natural areas, or that’s what I tell myself.
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Well, I do not eliminate it either, because the forest outside is already very infested with it. I can not fix the forest by removing the little bit in my garden. I actually planted it at a former home in town. There was not place for it to escape to.
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Awful miniature kudzu!
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Yes, but it does not climb.
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