From our perspective as plants, water is the very essence of our existence. For us hydrangeas, it is particularly crucial. Our large, thin leaves have a tremendous surface area from which water evaporates rapidly, especially on hot, sunny, or windy days. This transpiration process pulls water up from our roots to our leaves and flower heads. Without a consistent and ample supply of moisture in the soil, we cannot maintain the turgor pressure that keeps our leaves and blooms firm and vibrant. We begin to wilt, a clear distress signal. Chronic underwatering forces us to conserve resources, resulting in stunted growth, fewer blooms, and increased susceptibility to pests and diseases as our natural defenses weaken.
As the soil warms and daylight increases, we break our winter dormancy. This is a period of intense energy expenditure. We are pushing out new leaves, developing sturdy stems, and forming the initial buds that will become our iconic flower heads. This explosive growth requires a significant amount of water to transport nutrients and facilitate cell expansion. During this season, we need the soil around our roots to be consistently moist, but never waterlogged. A deep watering that encourages our roots to grow downward is far more beneficial than frequent, shallow sprinklings. Check the soil about 2-3 inches down; if it feels dry, it is time for a long, deep drink.
Summer is our most demanding season. We are in full bloom, our leaves are working overtime in the sun, and high temperatures accelerate evaporation. This is when our thirst is at its peak. We will likely need watering several times a week, and possibly even daily during intense heatwaves. The goal is to prevent us from wilting in the first place, as wilting is a sign of severe stress. A generous layer of organic mulch around our base (but not touching our main stem) is immensely helpful. It acts as a blanket, cooling our roots and drastically reducing moisture loss from the soil, allowing us to access water for longer periods between waterings.
As the air cools and our blooms begin to fade, our water needs start to decrease. However, this does not mean you should neglect us. We are still actively photosynthesizing and storing energy in our roots for the winter ahead. This stored energy is what will fuel our spring awakening. Gradually reducing the frequency of watering helps us acclimate to the coming colder weather. It is crucial to ensure we enter winter with adequately hydrated roots, especially for newer plantings. A well-hydrated root system is far more resilient to the freezing and drying winter winds.
Our above-ground growth has ceased, and we are in a state of dormancy. Our water requirements are minimal, but they are not zero. Especially in regions with dry winters or periods without snow cover, the soil can lose moisture to cold, drying winds. This can lead to desiccation, where our roots are damaged because they cannot draw water from the frozen ground. A deep watering in late autumn, before the ground freezes solid, is our best defense. For container-grown hydrangeas, an occasional check during a winter thaw is appreciated, as our pots can dry out completely even in the cold.
