From our perspective, winter is not a time of death but a period of deep, essential rest called dormancy. As daylight shortens and temperatures drop, we receive clear environmental signals to begin our shutdown process. We halt all new growth above ground, as tender leaves and stems are vulnerable to freezing. Instead, we redirect our energy downward, storing vital carbohydrates and nutrients in our root systems and the protected stems below the soil line. This dormant state drastically reduces our metabolic activity, allowing us to conserve energy and withstand freezing conditions that would otherwise be fatal.
Not all parts of our being are equally equipped for the cold. Our root systems, insulated by the soil, are generally hardy survivors. The primary point of vulnerability lies in our flower buds. For many hydrangea varieties, particularly the beloved Bigleaf hydrangea (*Hydrangea macrophylla*), these buds are formed on the previous season's growth ("old wood"). These buds, which hold the promise of next summer's blooms, are highly susceptible to desiccating winds and severe frosts. A harsh winter can kill these buds, resulting in a plant that survives but fails to flower. Our tender new stems can also suffer dieback from the tips downward.
Our ability to survive winter is deeply rooted in our genetics, which dictates our USDA hardiness zone tolerance. It is crucial to know which type of hydrangea you are nurturing. The Panicle hydrangea (*Hydrangea paniculata*), for instance, is a remarkably resilient species, often thriving as far north as zone 3. We form our flower buds on new growth each spring, so even if our stems die back, we can still produce a magnificent display of blooms. In contrast, our Bigleaf and Oakleaf (*Hydrangea quercifolia*) cousins are more sensitive, with their flower bud survival being the key to their floral success.
Your intervention is a welcome form of assistance that mimics the protective blanket of a forest floor. After the first hard frost kills our leaves and signals true dormancy, applying a thick, 12-18 inch layer of mulch around our base is immensely beneficial. Use shredded bark, leaves, straw, or pine needles. This layer does not heat us but instead maintains a consistently cold temperature, preventing the damaging cycle of freeze-thaw-freeze that can heave our roots from the ground. It also conserves crucial soil moisture, as we can still lose water from our stems during sunny winter days.
Beyond the roots, our exposed stems face the dual threats of winter sun and drying winds. These elements can cause desiccation, where we lose more water through our stems than we can replace from the frozen ground. For smaller specimens, creating a windbreak with burlap or landscape fabric stapled to stakes can be life-saving. Avoid using plastic, as it can trap excessive heat on sunny days. For taller, more established plants, simply leaving the dried, brown flower heads on throughout winter provides a surprising amount of protection to the delicate buds lower down on the stem.
