When to Plant Common Periwinkle

Seeds

• Common periwinkle seed may be planted in spring after all danger of frost or in early fall, long before the first frost. Alternately, it can be seeded indoors at any time of year, provided the indoor area receives at least a half-day's worth of sun and does not freeze. Later, when frost is no longer a threat, common periwinkle can be planted outdoors.

Transplants

• Transplants are best set out in the garden in early fall. This gives the roots time to establish long before the frost and frost heaving begin. Frost heaving occurs when the subsoil freezes and temperature and moisture differences cause the ground to shift dramatically. During the winter, common periwinkle will go dormant then come up strong from the established root system in the spring. It can also be transplanted in the spring to take advantage of the mild weather, but plants will be slow to grow until the following spring.

Hardiness Zone Differences

• Common periwinkle is hardy from USDA Zones 3 to 8. In the southern zones (primarily Zone 8), it's better to wait until the last August and September heatwaves are done before trying to plant. In the northern zones (Zones 3 and 4), there's a race to the first frost, so planting in early to mid August is the best choice.

Considerations

• Planting perennials, such as common periwinkle, in the evening or on cloudy days helps reduce the chance of heat- and sun scorch-related plant shock. However, common periwinkle can tolerate quite a bit of shade. If planting them in dappled shade, this is less of an issue. If planting them in a morning sun/evening shade situation, just wait for the shade to drop over the area before planting them.