The Garden Pest That Might Be Killing Your Hydrangeas Below Ground

The Garden Pest That Might Be Killing Your Hydrangeas Below Ground

Hydrangeas are a popular choice among gardeners as they not only provide a burst of color to landscaping but also occupy a lot of space with their large, bushy blooms. With their hues ranging from white to pink to blue, they can add a touch of elegance to a backyard or boost the curb appeal of a front yard. However, they can also spoil your garden design when they wilt and die. If you observe that your hydrangea flowers are turning brown, it could be due to pests. While most gardeners would suspect that black vine weevils or nematodes are the culprits, there is another unexpected pest that might be responsible: voles, which eat hydrangea roots.

Voles are tiny rodents resembling a cross between a mouse and a hamster. Although they may look cute, they can cause significant harm to your garden and plants because they mostly reside underground, creating vast networks of burrows to move around. Here’s how to determine if voles are damaging your hydrangeas and what to do about it.

How to know if voles are killing your hydrangeas

vole in grass

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One way to tell that voles are the culprit behind your dying hydrangeas is to look for teeth or gnawing marks on the plant. You can see them everywhere, from the branches to the leaves. You will know it’s them in particular based on how the marks look. They’re messy eaters, so the teeth marks will be haphazard and inconsistent. Their bite marks are also very small — they should be around 3/8 of an inch long. You can also see them on the roots. Hungry voles will munch away on the roots until the plant begins to die. To check, give one of the hydrangeas a tug. If the plant easily comes up — and the roots are cut back — you can likely thank a vole for that.

The next thing to look for is pathways and burrow holes. Voles create organized pathways on the grass or dirt to connect their tunnel holes on the outside, so see if you can spot any near the hydrangeas. The paths are usually only 1 inch wide, and look similar to pathways people make when repeatedly cutting across the grass over and over.

How to repel voles from your hydrangeas

mowing tall grass

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To save your hydrangeas from hungry voles, you will likely need to engage in eradicating these animals from your yard rather than merely repelling them. DIY repellents are often a hit or miss and aren’t backed by solid research, so you risk the chance of them coming back. To remove them from your property, the first step is to make your backyard a little less vole-friendly. They rely on tall grass, heavy mulch, or bushy vegetation to hide from predators, so make sure your grass is always short, push away heavy mulch from your hydrangeas, and make sure you don’t have overgrowth or leaf piles anywhere.

Next, you want to reduce their population with traps. Extension experts recommend using mouse traps with peanut butter to catch them. If you’re worried about a pet or other animal sniffing around these traps, you can put a can over the device with a small, vole-sized hole, allowing only them to enter. This, of course, will only be effective if you have a small vole problem. If you suspect an infestation, call a wildlife or exterminator expert to remove them for you.

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Dr Heidi Parkes

By Dr Heidi Parkes

Senior Information Extension Officer QLD Dept of Agriculture & Fisheries.