The Spirea Mellow Yellow (Spiraea thunbergii "Ogon") is a deciduous flowering shrub. It is among one of the first shrubs to bloom, producing beautiful white flowers in the spring. Its yellowish-green leaves, which turn orange-pink to reddish-salmon in the fall, hang from graceful, arched-shaped branches. Well-suited for perennial beds and foundation plantings, it grows to a height of 4 feet.