Known for their showy flowerheads in shades of pink, blue, white and purple, hydrangeas are some of the most recognizable and popular flowering shrubs available. They're also excellent as cut flowers. Hydrangea shrubs are available in many types, including oakleaf, panicle, macrophylla and serrata. Some hydrangea flowers are pH dependent, meaning their flowers become bluer in acidic soils and pinker in alkaline soils. Other hydrangea varieties have stable flower colors that don't change with the soil pH. When selecting hydrangeas for the garden, take into account their hardiness zone, sunlight requirements (full sun, partial shade, or full shade), soil requirements, mature height and spread, and flower color. Smaller hydrangea varieties are available that are suitable for containers.