Not all azaleas are evergreen. Azaleas are a varied group of flowering shrubs belonging to the genus Rhododendron, and their winter foliage habits fall into two distinct classifications. The specific type and the climate in which it is grown determine if it retains its leaves through the cold season or sheds them entirely. This difference dictates where the shrub can thrive and the specialized care it requires to survive winter.
Understanding Evergreen Versus Deciduous Azaleas
The difference between these two types is rooted in their botanical structure and adaptation to cold. Evergreen azaleas, primarily classified under the subgenus Tsutsusi, are not truly evergreen. They are dimorphic, producing two sets of leaves annually: thin spring leaves that are shed in the fall, and smaller, thicker “summer” leaves that persist through the winter months. This leaf retention allows the shrub to maintain its green appearance year-round, although some varieties are semi-evergreen and may lose most of their foliage in harsh winters.
Deciduous azaleas, belonging to the subgenus Pentanthera, follow the seasonal cycle of leaf drop. These shrubs shed all of their leaves in the autumn after they often display brilliant fall color, leaving bare stems throughout the winter. This complete leaf drop signifies a deep dormancy. These varieties are more cold-hardy than their evergreen counterparts, with some native North American species tolerating temperatures as low as -45°F. The loss of foliage is a survival strategy that prevents moisture loss when the ground is frozen.
Practical Differences in Winter Care
The retention of leaves in evergreen azaleas creates challenges for winter survival that deciduous types avoid. Since evergreens continue to transpire, losing water through their leaves, they are highly susceptible to desiccation or “winter burn” when the ground is frozen and roots cannot replace lost moisture. Gardeners must provide supplemental water to evergreen varieties whenever temperatures rise above 45°F in the fall and early winter, ensuring the soil is well-hydrated before a deep freeze.
Evergreen azaleas often require protection from harsh winter sun and drying winds, which can rapidly draw moisture from the foliage and cause leaf scorching. Planting them in a location shielded from the afternoon sun, such as an eastern or northern exposure, helps mitigate this risk. Deciduous azaleas, conversely, need no special attention once they have dropped their leaves, as their bare stems are fully dormant and highly resistant to cold damage.
Pruning timing is subtly affected by the classification. Both should be pruned immediately after their spring bloom to ensure flower bud set for the following year. Heavy rejuvenation pruning on deciduous types can sometimes be performed later in the dormant season. The compact, shallow-rooted nature of many evergreen varieties means they benefit from a thick layer of winter mulch to insulate their roots and conserve soil moisture.
Identifying Common Varieties
Many of the widely planted, low-growing varieties used in foundation plantings, particularly the Kurume and Southern Indica hybrids, are evergreen or semi-evergreen. The popular Encore Azaleas, known for reblooming, are modern hybrids bred to be hardy evergreen types. These often retain foliage in USDA Zones 6 through 10.
Deciduous varieties often originate from species native to the colder regions of North America and Europe. Examples include the Northern Lights series, bred for extreme cold tolerance, and the showy Ghent and Exbury hybrids. These types are recognized by their upright, open growth habit. Their flowers frequently possess a noticeable fragrance, a trait uncommon among many evergreen azaleas.