For Colorado gardeners, spring is an excellent time to plant many bulbs, seeds and starts for summer bloom. Colorado State University recommends all spring gardeners incorporate an inch of compost or other organic matter into garden beds to create nutrients. After choosing sites and preparing soil, Colorado gardeners can get ready for spring with several colorful flowers.
Dahlia can be planted either from a bulb or from a start. Available in nearly every hue except for blue, the dahlia grows in part shade to full sun. Spring-planted dahlias will bloom throughout the summer and fall and may grow up to two feet tall. The flowers resemble pom poms. Dahlia requires frequent watering and dislikes heat. Mulching the soil can help keep these flowers cool during hot weather.
Gladiolus corms should be planted in spring in Colorado for summer blooming. This tall-growing flower prefers full sunlight and should be planted at the back of a bed so blooms don't shade other plants. Gladiolus flowers require frequent watering, so avoid planting near other flowers with less stringent watering needs. Gladiolus comes in all hues, from white or red to lime green, according to Colorado State University.
Coreopsis grows best from seed and can be sown directly into your Colorado garden in the spring for blooms from May to September. A member of the sunflower family, coreopsis is yellow with patches of red or brown coloring. Plant the coreopsis in full sun. Native to prairies and plains, this flower can withstand low watering.
Sometimes called beardtongue, penstemon develops bright trumpet-shaped flowers in the summer. Native to the western United States, penstemon is a prairie plant that enjoys hot, sunny conditions. Penstemon may be white, pink, fuchsia, blue or purple in color. These flowers should be planted in the spring in Colorado from starts, not from seed. Penstemon varies from one to three inches in height. These are low maintenance garden flowers once planted.