From our perspective as hydrangeas, our primary request is for consistent moisture. Our fibrous root systems are relatively shallow and fine, making us susceptible to drought stress. The goal is not to have our roots sitting in perpetually waterlogged soil, which suffocates us and leads to root rot, but to reside in soil that feels like a well-wrung-out sponge—moist but aerated. This consistent moisture level is crucial for supporting our large, soft leaves and abundant blooms, which lose water rapidly through transpiration, especially on hot and windy days.
You cannot apply a one-size-fits-all schedule, such as "once a week," because our thirst is dictated by your local environment. The main factors we respond to are:
Climate and Season: In the hot, dry summers of the Southwest (USDA zones 8-9), we will require significantly more frequent watering—potentially every day during a heatwave—compared to a cool, humid Pacific Northwest summer (zones 7-8) where natural rainfall might suffice for longer periods. During our dormant period in winter, our water needs are minimal.
Sun Exposure: A hydrangea planted in full, afternoon sun will transpire water much faster than one enjoying dappled shade or morning sun only. More sun equals more frequent watering checks.
Soil Type: This is critical. Sandy soil drains extremely quickly and does not hold moisture well, requiring more frequent, lighter watering. Heavy clay soil holds water for a long time but drains poorly, requiring less frequent, deeper watering to avoid saturation.
The most reliable method to understand our needs is to check the soil directly. Insert your finger 2-4 inches into the soil near our base. If the soil feels dry at that depth, it is time to water thoroughly. If it still feels moist, check again the next day. Please also learn to read our physical signs. When we are thirsty, our large leaves will become visibly limp, droop, and may even feel soft to the touch. This is an urgent call for water. If we are receiving too much water, our leaves may turn yellow and drop, and the base of our stems may become soft and mushy.
When you do water, please do it properly. We prefer a long, slow, deep watering session that encourages our roots to grow downward into the cooler soil, making us more resilient. A quick splash from a hose only wets the surface and encourages shallow roots, which are vulnerable to heat. Apply water directly to the soil at our base, avoiding wetting our leaves and flowers, as this can promote fungal diseases like powdery mildew. A soaker hose or drip irrigation system is ideal for this. A generous layer of organic mulch (2-3 inches) around our base is immensely helpful. It regulates soil temperature, suppresses weeds, and most importantly, drastically reduces moisture evaporation from the soil.
