Azaleas are diverse, flowering shrubs of the genus Rhododendron. They can be classified into two subgroups: Tsutsuji (evergreen azaleas) and Pentanthera (deciduous azaleas). Azaleas grow natively in temperate regions across Asia, Europe and North America. Azaleas vary widely in form and appearance. They can grow as low ground cover 30 centimetres (12 inches) tall or reach a height of up to 3 metres (10 feet). Deciduous azaleas typically have tubular flowers with long stamens, while evergreen azaleas have many different flower forms. Some varieties of this shrub can overwinter outdoors with little protection, others are not cold hardy and will only thrive in greenhouses or indoors.