'Periwinkle' can refer to plants with quite different habits and cold tolerance. Before buying one for a bed or container, check the botanical name rather than relying on the common name alone.
A warm-growing bedding plant and a hardy spreading garden plant are not interchangeable simply because their flowers look familiar. The label should settle the identity before you decide where to plant it.
Match the plant to its job
Ask about mature size, spreading habit, light and local winter requirements. For a pot near a doorway, consider whether you want an upright seasonal display or trailing growth. For a garden bed, consider what happens after the flowers finish.
If the label is missing, ask the nursery to identify the plant. A photograph of one flower may not be enough for a reliable answer.
Keep the name with your planting record. If the plant later struggles, that identity is the starting point for useful advice about water, feeding and seasonal care. Without it, even a careful routine may be based on the wrong periwinkle.
Related reading: Periwinkle Care: Watering, Pinching and Propagation.