Why Your Hydrangea Plant Leaves Have Holes (& The Best Way To Prevent It)

Did you just notice a bunch of holes in the leaves of your beloved hydrangea and are wondering what could have caused them? Before you begin frantically spraying your plant with random insecticides, you need to get to the bottom of the issue. Although there are some common preventions to tackle leaf infestations, no matter the plant species or cause, you will be better equipped to fix the problem once and for all if you know which perpetrator is causing the damage. 

The tender foliage of your hydrangeas face constant threat from various sources. Pests such as Japanese beetles, caterpillars, and aphids eat the leaves and suck the sap; nocturnal trespassers like slugs and snails nibble on foliage; and microbes like fungi and bacteria cause infectious legions. While the damage inflicted is often more cosmetic than health-endangering, the best way to prevent these incursions is to keep your plants healthy and dry and get rid of the pests — either by hand or chemically — as soon as you notice them.

Leaftier moth caterpillars stitch hydrangea leaves together with silk to create a feeding shelter. To get rid of them, simply open up the leaves with your hands and remove the hidden culprits. Japanese beetles may also damage hydrangea foliage. It is easy to identify their work by the skeletonized leaves they leave behind after they are done feasting on the tissue between the veins. Rose chafers, when abundant, can inflict similar damage, skeletonizing leaves as well as flower petals. On the other hand, sap-sucking insects such as aphids and squash bugs are more likely to damage young growth, causing weeping holes alongside mottled and discolored leaf surfaces. To save your leaves, simply sweep the insects off into a container full of soapy water or use a strong spray of water to keep them at bay. Think twice before using traps to get rid of pesky Japanese beetles especially. They may have the opposite effect, drawing more beetles to your yard.

Holes in hydrangea leaves could also be caused by slugs, which you can identify by the slimy residue they leave behind as they travel around the plant. Slugs are more active in humid weather, particularly when a hydrangea is in the developmental stage. During wet weather, snails may do similar damage to a hydrangea's tender leaves, particularly if the plant is growing in shady areas. The best way to deal with slugs (and snails) is to get rid of their hiding places and set up beer or grapefruit traps as an all natural way to help catch and remove them from your yard and garden.

Leaf spot, a common lawn disease, is one of the primary possible non-pest causes of holes in hydrangea leaves. The condition weakens the leaf and can eventually cause a hole right in the center; the leaf gradually becomes yellow and falls off. You might also see black and brown spots on the underside of the leaves and a red halo around the hole. Bacterial leaf spot is prevalent in late spring through early summer, particularly in oakleaf hydrangeas (Hydrangea quercifolia). Since the disease first appears in the lower foliage of the plant and spreads upwards via overhead irrigation or rainfall, you can control it by removing the lower leaves as soon as you begin to see the spots.

A number of other fungal diseases, such as Anthracnose and Cercospora, may also be a cause. They have similar symptom patterns, beginning as light-hued spots that eventually turn brown and leave holes in the leaf. The reasons behind the onset of these diseases is usually environmental, like lack of air circulation and overcrowding; prevention centers on addressing these issues. Space your plants far apart and monitor your watering schedule so that the leaves are not wet overnight when they are most vulnerable to microbial infection.