March and early April is the bloom time for the cornelian cherry dogwood, a tree native to Europe that grows in US Department of Agriculture plant hardiness zones 4 through 8. The yellow flowers, blooming before foliage develops, form clusters of star-shaped blossoms.
Golden garlic, winter aconite, many daffodil and tulip cultivars and the Golden Yellow snow crocus emerge from bulbs and produce yellow flowers. Golden Yellow blooms in April, growing to 6 inches high and goes dormant after flowering by late spring. Lily of the Incas comes in a hybrid form known as Sweet Laura that has rigid, erect stems that produce a yellow flower in June that lasts into September. The flower is cold hardy to USDA zone 5.
Yellow flowers are a staple of the Japanese barberry, but cultivars such as Aurea double the yellow by featuring golden-colored foliage. Bogozam is a dwarf form that grows to 24 inches high. Another deciduous shrub featuring yellow flowers is winter hazel, blooming sometimes before the calendar says spring in zones 6 through 8. Witch hazel has a late bloom time, with its yellow flowers appearing in autumn. Forsythias possess yellow flowers as well, with cultivars such as Happy Centennial and Courtasol available in nurseries.
Pot marigolds, clasping coneflowers, some impatiens and many types of creeping zinnias are annuals with yellow flowers. Containers and flowerbeds are appropriate settings for the French marigold, an annual for full sun that grows to 12 inches high. Known for its aromatic foliage, this marigold blooms in June and it stays flowering until first frost. Keep the sunflower cultivar Sungold out of windy sites; the breezes may knock it down, since it grows to 10 feet. The yellow flowers are as wide as 10 inches on this annual.