Last week, we talked briefly about types of plant dormancy and why it happens, specifically focusing on deciduous plants which lose their leaves each season. Evergreen plants like holly, wax myrtle, pines, and camellias have interesting adaptions that allow them to keep their leaves year-round.
Evergreen species rely on several external traits to help them survive winter while retaining their leaves. Some, like cedars and pines, have narrow needles or flattened sprays of foliage instead of broad leaves. These small, compact leaf shapes reduce water loss during cold, dry, and windy weather and, in snowy climates, help prevent snow from accumulating and breaking branches. Broadleaf evergreens such as holly and camellia keep wider leaves, but they are protected by a thick, waxy coating that reduces moisture loss and shields the leaf surface from wind and freeze injury. Evergreen foliage also tends to be darker in color, allowing it to absorb more heat from the sun. In addition, evergreen branches are generally more flexible than those of deciduous species, enabling them to bend under snow and ice rather than snap. Together, these external adaptations help evergreens withstand winter conditions that would damage plants relying solely on dormancy.
In addition to external adaptions, there are a few things that happen inside the plant. Because they retain their leaves, evergreen plants are able to continue capturing sunlight and using photosynthesis to produce energy, though at a slower rate than during warmer seasons. Since photosynthesis is slowed, the plant doesn’t grow much during winter, which conserves energy and water resources. Possibly the most interesting part of evergreen plants is how their internal tissues adapt in the winter: evergreen tissues accumulate a mix of salts and sugars that lowers the freezing point inside their cells. This “antifreeze” system is important, because when water freezes it expands, which can damage plant cells. The roots of evergreen plants remain active through winter as long as soil temperatures stay above freezing. Because the risk of desiccation, or moisture loss, is much higher in winter, evergreens rely on adequate soil moisture to avoid drying out. Applying mulch around the root zone helps insulate the soil and conserve water during cold, dry periods.
Even healthy evergreen species may experience a seasonal needle drop, which can be mistaken for disease. During this process, older inner needles will turn yellow and fall off the plant, while the newer outer needles remain green and healthy. This gradual cycling of leaves ensures that the plant has enough leaves to survive while getting rid of tissue that may attract disease or pests.
Evergreen plants are uniquely adapted to survive winter conditions and provide wonderful visual appeal in seasons where other plants are dormant. For questions about evergreen care or landscape management, contact us at 706-359-3233 or uge3181@uga.edu
