Greetings, concerned caretaker. From our perspective here in the plant world, those holes in your hydrangea leaves are a clear signal—a message that something is disrupting our peaceful existence. We cannot speak in your tongue, so we use our foliage to communicate. Let me explain the most common reasons for this perforated plea for help.
This is the most frequent cause of the holes you see. Unlike the microscopic pests that suck our sap, the culprits here are larger insects with mandibles designed for tearing and chewing. They take bites directly out of our leaf tissue, leaving behind irregular holes or even skeletonizing the leaves, leaving only the veins. The usual suspects include caterpillars (the larval stage of moths and butterflies), beetles (like the Japanese beetle, which is particularly fond of us), and slugs or snails (which leave a tell-tale silvery slime trail). These creatures see our broad, succulent leaves as a prime food source. From our point of view, this is a direct attack on our solar panels, reducing our ability to photosynthesize and create the energy we need to grow and produce those beautiful blooms you admire.
Not all damage is caused by living creatures. Sometimes, the holes are the result of physical trauma from the environment or accidental harm. Hailstorms can brutally pelt our leaves, punching holes and tearing the delicate tissue. Strong, whipping winds can cause branches to rub against each other or against fences, shredding the leaves caught in between. Even well-meaning gardeners can accidentally snag a leaf with a tool or brush past us too roughly, causing a tear. While this damage is not caused by a pest, it still weakens us. The injured edges of these holes often turn brown and crispy as the leaf attempts to seal off the wound, much like a scab forms on your skin.
Sometimes, the holes are not initially caused by chewing, but by disease. Fungal infections, such as Cercospora leaf spot or Anthracnose, can create spots or lesions on our leaves. Initially, these appear as discolored circles or blotches. As the disease progresses, the tissue within these spots dies, becomes dry and brittle, and eventually falls out, leaving a hole. So, what you might be interpreting as insect damage could actually be the final stage of a fungal problem. This type of damage indicates that our internal systems are under stress, often exacerbated by humid conditions, overhead watering, or poor air circulation that allows these pathogens to thrive.
It is also important to consider our overall health. A hydrangea that is stressed is far more susceptible to all the issues mentioned above. If we are not receiving the right amount of water (either too much or too little), if we are planted in soil that doesn't suit our needs, or if we are not getting the appropriate amount of sunlight, we become weak. A stressed plant is like an immune-compromised individual; we cannot defend ourselves as effectively. Pests are naturally drawn to us when we are vulnerable, as we are an easier target. Therefore, the holes in our leaves might be a secondary symptom of a primary problem related to our growing conditions.
