To understand pruning, you must first understand me. I am not a single plant but a genus with several primary species, each with a distinct growth habit. My blooming strategy is the key. I, the Hydrangea, fall into two main categories: those who bloom on "old wood" and those who bloom on "new wood." "Old wood" refers to stems that have been on the plant since the previous growing season. "New wood" refers to the current season's growth. Pruning me at the wrong time means you are cutting off the very stems that hold the promise of my beautiful flowers.
If I am a Bigleaf hydrangea (the classic mophead or lacecap), an Oakleaf hydrangea, or a Mountain hydrangea, I set my flower buds in late summer on the stems from the previous year. This means my bloom potential for next spring is already waiting, dormant, on those stems. If you prune me in the fall or spring, you will be cutting off those precious buds, and I will not be able to produce blooms for you that year. The best time for any pruning is immediately after my flowers fade in mid-summer. This gives me just enough time to produce new growth that will harden off ("set buds") before winter arrives. Please, only remove spent flowers (deadheading) and any dead or crossing branches at this time.
If I am a Panicle hydrangea (like 'Limelight' or 'Grandiflora') or a Smooth hydrangea (like 'Annabelle'), I am much more forgiving. I produce my flowers on the new growth that emerges in the spring. This means you can prune me in late winter or early spring, while I am still dormant, and I will still bloom for you that same year. In fact, a harder prune often encourages me to produce stronger stems and larger flower heads. You can cut my stems back by as much as one-third to one-half of their height. This is also the ideal time to remove any weak or spindly growth to improve my overall shape and structure.
When you approach me with shears, please see it as a conversation. Your goal is to help me direct my energy. Always make clean, angled cuts just above a set of healthy leaf buds. This signals to me to send energy to that bud, encouraging outward growth and preventing a dense, tangled center that inhibits air circulation. Remove any stems that are dead, damaged, or diseased first, cutting them back to their point of origin. Then, thin out about a third of my oldest stems to rejuvenate me and encourage new, vigorous growth from the base. This process, whether done in summer or late winter, helps me stay healthy and strong, which is the true secret to more blooms.
