Vinca minor, also known as Common Periwinkle, a plant species originally native to parts of central and southern Europe. Commonly used and referred to as a 'groundcover,' Vinca minor is often used to cover bare places of ground and is dense in its nature of growth. It has a habit that often chokes out competing plants and weeds, Periwinkle is excellent in preventing soil erosion. Vinca minor tends to bloom throughout the spring and summer months.

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The periwinkles in the genus Vinca open their first flowers quite early, when crocuses are in full bloom and as daffodils start to flower. Periwinkle flowers are a lovely shade of blue-purple, pink, red or white, which is well enough known to appear in poetry and clothing catalogs as a color name

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Periwinkles are evergreen in most of Europe so are available all year for chaplets. The blue color made periwinkles flowers of heaven and symbols of Jesus, Mary and the angels in Heaven, so in medieval Europe one might carry or wear periwinkles as a reminder of Heaven and its grace.

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Periwinkles (the plants) have a rich history in Europe, having been used medicinally since at least Roman times. Dioscorides (64 AD) wrote that the leaves and stalks drunk in wine stop dysentery and chewed, the leaves cure the pains of the teeth. That's just a bit of the folklore of periwinkles.

text from multiple Google sources