From my perspective as a plant, my ability to flower is heavily dictated by your pruning schedule. My stems are not all the same; some are old wood, and some are new wood. For many of us hydrangeas, particularly the beloved Bigleaf varieties (Hydrangea macrophylla), we set our flower buds on old wood. This means the buds for next summer's spectacular show begin to form shortly after we finish blooming this year, maturing and hardening on the stems through the fall and winter. If you prune me in the late fall, winter, or early spring, you are very likely cutting off these precious, pre-formed flower buds. You are essentially removing my entire blueprint for blooming before I even get a chance to use it.
Light is my food, my clock, and my energy source. The amount I receive directly dictates my resources for blooming. If I am planted in deep, full shade, I simply cannot photosynthesize enough energy to produce those large, lavish flower heads. My survival becomes the priority, and blooming is a luxury I cannot afford. Conversely, if I am baking in intense, all-day sun, especially in hotter climates, I become stressed. My leaves may scorch, and I will spend all my energy and water reserves trying to stay cool and hydrated, again leaving little for flower production. I thrive best in a location with gentle morning sun and dappled or partial afternoon shade.
What you feed me, or don't feed me, has a profound effect. I require a balanced diet to perform. A common mistake is applying a fertilizer too high in nitrogen. This nutrient promotes vigorous, green, leafy growth at the expense of flowers. It tells my system to focus on building a bigger body, not on reproduction (blooming). Alternatively, if the soil is very poor and I am starved of nutrients altogether, I won't have the basic building blocks to create blossoms. I prefer a fertilizer that is balanced or one that is higher in phosphorus (the middle number in the N-P-K ratio), as phosphorus specifically supports root development and flower production.
For those of us who bloom on old wood, winter is a dangerous time. Those tender flower buds I worked so hard to create in the fall are highly susceptible to freezing temperatures and late spring frosts. A sudden cold snap can easily kill them. Once dead and brown on the inside, they will not magically revive to produce a flower come summer. This is why a harsh winter or an unusually late frost can result in a spring full of healthy green leaves but a complete absence of blooms. You might not see any outward damage to the stems, but the crucial buds are gone.
Please be patient with me if I am a new addition to your garden or if you have recently moved me. The process of transplanting is incredibly stressful. My entire world is upended, and my root system, which is my mouth and my anchor, has been significantly disturbed. My immediate biological imperative is not to flower but to survive. All of my energy will be directed inward to re-establish my roots in this new location and regain my strength. It is very common for me to take a year, or sometimes two, to become fully settled and confident enough in my environment to direct energy away from root growth and towards the magnificent display of flowers you desire.
