Spring-planted perennials, such as black-eyed Susans, salvias and daylilies, are long-lived, but slow-growing flowering plants that are generally grown from nursery-grown plants. Annuals, including nasturtium, petunias, and pansies, grow quickly, but are frost tender and live only one season. Summer-blooming bulbs, such as gladiolus, cyclamens and dahlias, are planted in spring.
Roses and a few other cold-hardy perennials are planted early in the spring, as soon as the soil is soft enough to work. Most perennials, annuals and summer blooming bulbs, though, are planted in late spring after the last expected frost, but before temperatures climb.
Perennials represent a permanent investment in the garden, so good soil pays off. According to Cornell University, 3 to 6 inches of organic material, such as compost, tilled into the garden before planting improves drainage and soil fertility. Bulbs and annuals also benefit from good soil.