Limelight hydrangea has a pleasing, mounded shape, but it's the blooms that attract attention. In northern climates, the shrub flowers from late summer through late fall. Along the Gulf Coast, the green blooms appear as early as late May and June. The large flower clusters, known as panicles, have a broad, pyramidal shape. The clustered flowers start as deep lime buds that open to delicate green and progress to lime-tinged cream. Long-lasting as cut flowers, the green blooms are a florist favorite.