Common (or Small) Periwinkle was introduced from Europe and came to North America as an ornamental as early as the 1700s. It was chosen as an ornamental because it forms dense mats of evergreen leaves and pretty pale blue flowers. It is also highly adaptable and can be cultivated in a variety of different soil types and environmental conditions. Since its introduction, Common Periwinkle has escaped cultivation. It has formed monocultures in unintended areas such as forests, meadows, and watercourses.
Common Periwinkle is easily distinguished from other plants when it is flowering in May and June. However, when the flowers are not present, its green, dense foliage can be quite unassuming. The shiny dark green leaves are 3-9 cm long and are oval with a pointed tip. Common Periwinkle overtakes native plants, shading them out and stealing resources. Since it grows well on riverbanks, it can lead to erosion because its root system is much shallower than native plants it may have displaced. It also has a very sneaky tactic of producing biochemicals, which allow it to inhibit the germination and seedling growth of native plants, further suppressing native plant colonies. As if it can get any worse, Common Periwinkle is also inedible and is toxic to humans and animals!
Be sure not to plant Common Periwinkle in your yard and gardens and do not use it in landscaping. It is a pretty plant, but it is highly detrimental to native plants and the ecosystems in the Sea to Sky. You can learn about ornamental alternatives to Periwinkle in the Grow Me Instead booklet.