From my perspective as a hydrangea, those unsightly brown spots you see are the visible symptom of a much deeper conflict. It is an invasion, most commonly by fungal pathogens like *Cercospora hydrangeae* or *Anthracnose*. These organisms are not malicious; they are simply opportunistic. They land on my leaves from the air, in splashing water, or from infected debris below. When conditions are right—specifically, during periods of warm, humid, and wet weather—they germinate and penetrate my leaf tissue. The brown spots with sometimes darker purplish or reddish halos are the battle scars from this invasion, areas where the fungal hyphae are feeding on my cells, causing them to die and collapse.
You cultivate me for my lush foliage and magnificent blooms, providing ample water and often planting me in groups for a stunning display. Unfortunately, these very conditions that help me thrive can also create a perfect environment for the fungi. Overhead watering, especially in the evening, leaves my foliage wet for hours, giving the spores the moisture they need to germinate. Dense planting limits air circulation around my leaves, trapping humidity at the canopy level. Even your well-intentioned mulch, if piled too high against my stems (my collar), can create a damp, stagnant microclimate that encourages spore development and makes it easier for them to splash onto my lower leaves.
To help me fight back, we must change the conditions of the battlefield. First, please adjust your watering habits. Water me at the base, directly onto the soil, and ideally in the morning. This allows any accidental splashes on my leaves to dry quickly under the sun, depriving the fungi of their crucial moist environment. Next, improve air circulation. This might mean carefully pruning some of my inner branches to open up my structure or ensuring other plants are not crowding me. Crucially, practice excellent sanitation. As my infected leaves fall, promptly rake them up and dispose of them in the trash, not the compost. These leaves are covered in millions of spores waiting to re-infect me next season.
If the infection is severe or has recurred for several seasons, my own defenses may be overwhelmed, and I might need you to intervene with a fungicide. Think of these as targeted medicine, not a cure. For a gardener, the first line of defense should be a preventative, biological fungicide containing *Bacillus subtilis* or a horticultural oil like neem oil. These are gentler options that can suppress fungal growth. For more persistent cases, chemical fungicides containing chlorothalonil or thiophanate-methyl can be used. It is vital to follow the label instructions precisely, rotate between different types (modes of action) to prevent the fungi from developing resistance, and begin applications at the first sign of spots or before symptoms appear if it's a recurring issue.
