From our perspective as hydrangeas, winter is a time of essential rest, but also of great vulnerability. Our above-ground growth—the stems, leaves, and the precious flower buds you so admire—enters a dormant state. Our sap retreats down into our roots to avoid freezing in our cells, which would cause fatal damage. The primary threat is not the cold itself, but rather the rapid freeze-thaw cycles and the harsh, drying winter winds. These conditions can desiccate our exposed buds and stems, killing the embryonic flowers within before they ever get a chance to bloom in the spring. Our tender new growth, particularly on bigleaf (Hydrangea macrophylla) and oakleaf (Hydrangea quercifolia) varieties, is most at risk.
The most important protection you can offer us is at our base. Our root system is our lifeline, storing the energy we need to burst forth again in spring. A deep, insulating layer of mulch is akin to tucking us in with a thick, warm blanket. After the ground has frozen hard for the first time (this prevents rodents from nesting in the warm mulch), please mound 6 to 8 inches of loose, airy material like pine needles, shredded bark, or oak leaves around our base. Avoid using heavy, matting leaves or plastic, as they can suffocate our crowns and promote rot. This layer regulates the soil temperature, preventing the repeated freezing and thawing that can heave our roots right out of the ground, causing severe damage.
For our upper parts, the strategy is to break the wind and shield us from the harsh, drying sun. After our leaves have dropped and we are fully dormant, you can create a simple protective barrier. Driving four stakes into the ground around us and wrapping them with burlap or commercial frost cloth creates an effective windbreak. It is crucial that this covering does not touch our stems directly, as this can cause abrasion and hold moisture against us. The goal is to create a still-air pocket, not an airtight seal, which would lead to overheating on sunny days. For smaller hydrangeas, a cage of chicken wire filled with dry leaves can offer superb insulation for our entire structure.
Do not forget to water us deeply and thoroughly in the late autumn, before the ground freezes solid. We enter winter far more resilient if our root systems and stems are fully hydrated. Think of it as us storing water for the long, dry winter months. Desiccation, or winter drought, is a silent killer. When the ground is frozen, we cannot replace moisture lost from our stems and buds to the relentless winter winds. A well-hydrated plant is far more resistant to this drying effect. However, once the deep cold sets in, please cease watering, as excess moisture around our roots in frozen soil is detrimental.
Your care should not end with the last frost. The arrival of warmer weather requires patience. Resist the urge to remove our protective mulch and coverings too early. A late spring frost can easily destroy the new growth we've been protecting all winter. Wait until all danger of a hard frost has definitively passed in your area. Then, unwrap and remove the mulch gradually, over a period of a week or so, allowing us to acclimate gently to the new season. This careful attention in spring ensures the flower buds you worked so hard to protect will have their chance to develop and flourish.
