Many different herbaceous perennials, which die to the ground in winter, can be set out in early spring, giving them time to establish a good root system before warm weather arrives. Of those that thrive in full sun, daylilies (Hemerocallis spp.) are among the toughest and easiest to grow, producing large flowers with recurving petals in many colors. Examples include "Becky Lynn" (Hemerocallis "Becky Lynn") and "Catalyst" (Hemerocallis "Catalyst), with lavender and yellow flowers, respectively. Both grow in U.S. Department of Agriculture plant hardiness zones 3 through 10. If you'd like to brighten a shady spot with colorful flowers, choose astilbe plants (Astilbe chinensis), which love shade and have plume-like flowers above attractive foliage. Many astilbe cultivars exist, such as "Visons" (Astilbe chinensis "Visions"), which has pink flowers and grows in USDA zones 4 through 8.
Unlike perennials that bloom for only a part of each season, most annuals flower non-stop and can fill a bed with color for an entire summer. But annuals are frost-sensitive, so if you area has sub-freezing temperatures in early spring, wait to set out annuals until all danger of frost has passed. Among the many choices, petunias (Petunia spp.) love a sunny spot, but they also do well in partial shade. They're available as dwarf varieties, trailing groundcovers, or erect cultivars, with single or double flowers in many shapes and colors. For a shady spot, plant impatiens (Impatiens walleriana), an easy-to-grow plant that produces masses of flowers for the entire summer, in pink, rose, orange, white or bicolors. Both petunias and impatiens are grown as annuals, although they may survive winter in USDA zones 10 through 11.
Bulbs for Spring
Spring is a good time to set out certain types of bulbs that benefit from cool, moist spring weather to develop a strong root system. Lilies (Lilium spp.) are especially tough and dependable plants that grow from a bulb made up of fleshy, concentrically arranged scales. They come in many varieties, organized into groups called divisions. The variety "Casa Blanca" (Lilium "Casa Blanca") is a good example that's about 4 feet high, with large, 8-inch-wide, fragrant white flowers in summer. It grows in USDA zones 5 through 8. Plant it in very early spring. The gladiolus (Gladiolus spp.) is another good choice that grows from a bulb, producing tall, blooming spikes in many different colors. They do well in full sun or partial shade and grow year-round in USDA zones 8 through 10, but also work well as annuals in colder areas.
If you're looking for extra-large or impressive flowers, plant the hardy hibiscus (Hibiscus spp.) in early spring. It's a tough perennial with flowers often called "dinner plates" because of their size. The variety "Kopper King" (Hibiscus "Kopper King") is a good example that grows in USDA zones 4 through 9 and brings a summer-to-fall display of 10-inch wide, pinkish-white flowers atop burgundy foliage. If you have a mailbox post, fence or trellis, add a vining plant in spring, choosing one that blooms to add color and interest. For example, the clematis variety "Nelly Moser" (Clematis "Nelly Moser") grows in USDA zones 4 through 8 and climbs readily, with large, mauve-pink flowers covering the vine in May through June, or plant fragrant sweet peas (Lathyrus odoratus) once frost danger has passed. This avid climber has flowers in many colors and grows as an annual.