These days, nurseries are full of blooming flowers that can be planted almost any time the ground is workable. However, there are ideal planting times that ensure the longest possible season of color.
Annual flowers are categorized as cool season or warm season. Like the names suggest, cool-season annuals (such as Pansies, Violas, Calendulas and Primroses) bloom primarily in the cool months of spring and fall. They can withstand frost and are usually planted in late winter to early spring, about 6-8 weeks prior to the average date of the last frost. Cool-season annuals can also be planted in late summer for fall blooms and, in areas with mild winters, will often bloom all winter and into spring. Warm-season annuals like Marigolds, Zinnias, Cosmos and Petunias are frost sensitive and grow best in the heat of summer. They are best planted in spring after the danger of frost.
Flowering perennials are usually planted in fall but can also be planted in spring.
Hardy flowering bulbs, such as Tulips, Daffodils and Hyacinths, are best planted in fall. Tender bulbs like Gladiolus, Begonia and Caladium are tender bulbs and should be planted in spring after threat of frost.