Spring flower gardening in Colorado can be a challenge due to the combination of low humidity, poor soil conditions and rapid weather changes in the state. The bright side is that because of the high light intensity due to the high elevation, flowers grow well and their colors are quite brilliant. When planning a spring garden, consider how much sunshine the garden will receive and if the space is accessible for weeding and watering.
Bulbs are an excellent choice for spring planting in Colorado, according to the Colorado State University Extension. Locate the bulbs in a sunny spot with well-drained soil and plant them after the last spring frost. Bulbs to consider include dahlias; of which there are 12 different flower groups; calla lilies, which can be planted around other perennials; gladiolus, which are available in literally thousands of types; and elephant ears, known for their large leaves.
Plant annuals after the last spring frost. Annuals for full sun include yarrow, torch flower, flowering and jasmine tobacco, Mexican poppy, verbena, snapdragon, spider flower, cosmos, fountain grass, castor bean, rose mallow, the Dahlberg daisy and the black-eyed Susan, a native plant. For shady areas of the garden, consider wax begonia, coleus, impatiens and Madagascar periwinkle.
Perennials should be planted in the Colorado spring after the threat of frost has passed, or during the rainy season. There are several options for perennials, including native plants like the Rocky Mountain Columbine (the Colorado state flower), prairie coneflower, fleabane, dotted grayfeather, blue flax, Indiangrass and blanketflower. Non-native perennial choices include Russian sage, bellflower, red valerian, Mexican evening primrose and bloodred geranium. Perennial choices for shady areas include bergenia, foxglove, coral bells and foamflower.