Generally, the best time to plant perennials and shrubs is in the spring or fall. Cool temperatures, reliable rainfall, and short, bright days help plants make a quick and easy transition to your landscape. Depending on when you plant, make sure the threat of frost is gone before planting in spring and you provide at least 6 weeks before your ground freezes in fall. If you are unsure, mid-November is a safe planting deadline for nearly everyone in the U.S.