Yellow is one of the colors of the flowers of the flowering maple. This is not a member of the maple family, but belongs to the same group as mallows. A nearly tropical broadleaf evergreen, flowering maple is a hybrid growing to 10 feet in U.S. Department of Agriculture Plant Hardiness Zones 9 and 10, and to 4 feet as an annual in colder regions. The bush allamanda, golden trumpet and Jerusalem sage are other broadleaf evergreens for yellow blossoms. Mary Fleming is a rhododendron cultivar with dull-yellow flowers, exhibiting cold hardiness to zone 5.
The thorny Japanese barberry cultivar Maria not yellow April flowers and has yellow foliage lasting into autumn. It is an appropriate deciduous shrub for hedges, foundations and the edge of paths, growing to 4 feet. Certain butterfly bush cultivars feature yellow flowers, as does winter hazel, an Asian shrub growing to 15 feet. It turns out yellow flowers in March, often before winter officially ends in zones 5 through 8. Forsythia hybrids and cultivars; including Goldleaf, Sunrise and Arnold Giant; have possess brilliant-yellow flowers before their leaves grow out in early spring.
Golden Cross is a form of clematis suitable for small gardens growing to 6 feet long and generating yellow, cross-shaped flowers. It grows from USDA zones 4 through 9 as a vine. My Angel and Gravetye Beauty are two other clematis vines with yellow flowers. Columnea has flowers with yellow interiors, but this cold-sensitive Central American vine only survives indoors as a greenhouse species or a houseplant, except in zones 11 and 12. Grow the black-eyed Susan vine as an annual. It develops to 8 feet and gives you yellow flowers from late summer into autumn.
The yellow buckeye is a tree with yellow flowers, blooming in erect cluster called panicles in May. Yellow buckeye grows from USDA zones 4 through 8 and is used for as a shade tree on lawns. The cornelian cherry dogwood is a small tree growing to 20 feet and flowering yellow in early spring. Making its flowering even more impressive is a lack of leaves on the tree when it blooms. The golden rain tree, purging nut and the tulip magnolia also have yellow flowers.