If you only had time and space to grow five summer flowers, which ones would you choose? We asked ourselves that question last year. Flowers in dazzling colors topped our list—ones whose vivid hues would stop passersby in their tracks and invite lingering looks. We'd toss in a few varieties with eye-catching frills, spots, or stripes.

Philippe Glade
Starfire mix marigold

Our next criterion: They would be annual (or behave that way), going from seed, tuber, or seedling to flower to seed again in one glorious spring-to-fall season. They would be easy to plant and easy to grow. We wanted nothing that needed fussing over, nothing temperamental or wimpy. The flowers had to be good for bouquets or good companions for cutting flowers. We wanted ones that would bloom over a long season (as long as we were faithful about deadheading, of course).

We made a list and pared it down. We browsed through nurseries and catalogs, choosing plants that piqued our interest. Finally we planted many varieties of five flower groups in Sunset's test garden in Menlo Park, California.

As they grew, we studied their backgrounds, noting that all of them hail from hot climates. Cosmos originated in tropical America. Dahlias come from Mexico and Central America, where they were first used as food (their tubers contain a nourishing starchy substance not unlike a potato), while improved varieties bloomed lustily at Montezuma's gardens in Huaxtepec. The marigold family, despite French and African names, is entirely American, found from New Mexico and Arizona south to Argentina. Summer mums are native to Morocco and have naturalized in sand dunes along Southern California's coast. Sunflowers grow wild from Minnesota to the Pacific Coast and south to Argentina. (Red sunflowers descend from Helianthus annuus lenticularis, a variety found in 1910 near Boulder, Colorado.) Together, these groups make up a colorful and sunny brotherhood.

By early summer, there was an abundance of blooms that we enjoyed as much in bouquets as in the garden. Our vases were always full. And those electric colors did more than caffeine to jump-start our days. We made note of the duds and the stars. April is a splendid time to plant them all.