A number of spring-planted bulbs, including increasingly popular Dahlias, are only perennial in zones 9-10, tolerating winter temperatures only to about 20° F.
So for most of the country, they are most commonly replanted each growing season. For some gardeners, it is worth their while to dig or “lift" these cold-tender bulbs after hard frost and store them for replanting the next year. Others may let the bulbs freeze out over the winter and plant new stock in the spring.
Spring-Bulb Planting Tips: Don’t be in a rush to plant the heat-loving varieties like Canna Lily, Dahlia, Calla Lily, and Mexican Shell Flower. Wait until the last frost has passed and the soil has begun to warm up. When it’s time to plant tomatoes outside, it’s time to plant these bulbs. Similar to tomatoes, if you have a short growing season, consider planting bulbs in pots indoors to give them a head start, then transplant them outside when it's warm enough.
Among the spring-planted bulbs, there are a number of cold-hardy varieties that are reliably perennial. These flowers can be used in the mixed perennial flower border with great results. For best results, be sure to choose varieties that match your climate and growing conditions. Plant and enjoy the added layers of color and texture to enhance your perennial garden!