From my perspective as a hydrangea, the most common reason I fail to produce the beautiful blooms you expect is that my energy reserves were depleted at a critical time. Many of my popular varieties, like the classic mophead Bigleaf hydrangea (Hydrangea macrophylla), form their flower buds in late summer on the stems that grew that same season. These buds then wait patiently through fall and winter, protected by scales, to bloom the following year. If you pruned me in the autumn or early spring, you likely cut off these dormant flower buds. You were simply tidying up, but from my point of view, you removed my entire potential for flowering. All the energy I invested in creating those buds was wasted.
Patience is crucial. If you recently planted me, my primary instinct is not to flower but to survive. My first order of business is to establish a strong root system deep into the soil to secure water and nutrients. Flowering is an incredibly energy-intensive process for me. Producing those large, showy blooms requires a massive investment of resources that I, as a young plant, may not yet possess. I must feel secure and well-established before I can divert energy from root and leaf growth to the luxury of reproduction. It may take two to three years for me to mature enough to put on a significant floral display.
My location profoundly affects my ability to bloom. I am particular about my sunbathing habits. Too much intense, direct afternoon sun can scorch my leaves, causing me stress and forcing me to expend energy on repair rather than bud formation. Conversely, deep shade means I cannot perform sufficient photosynthesis to manufacture the sugars needed to create flowers. I thrive in dappled sunlight or morning sun with afternoon shade. Furthermore, inconsistent watering causes me great stress. Periods of drought will lead me to abort flower buds as a survival mechanism, while soggy, waterlogged roots can rot, preventing me from taking up any nutrients at all, effectively starving me.
Your fertilization habits directly influence my growth cycle. If you feed me with a fertilizer high in nitrogen, you are encouraging me to produce an abundance of lush, green leaves at the expense of flowers. Nitrogen promotes vegetative growth. To initiate and support flower bud development, I need more phosphorus (the middle number in a fertilizer ratio, like 10-20-10). However, timing is everything. Applying fertilizer too late in the season can stimulate a late flush of tender new growth that will be killed by the first frost, weakening me overall. A balanced, slow-release fertilizer applied in early spring is often what I need most.
This is a heartbreaking event from my perspective. After successfully forming my flower buds in late summer and protecting them through a mild winter, a sudden, hard late frost in the spring can be devastating. The tender, emerging bud tissue is extremely susceptible to freezing temperatures. When these buds are killed, they turn brown and dry up, never opening. This is a particular problem for my varieties that bloom on old wood. A single cold night can wipe out an entire season's blooms. A protective layer of mulch around my base in autumn can help insulate the roots and lower buds, but an unexpected spring freeze is often beyond my control.
