Common Hedge Problems and How To Treat Them

While hedges are tough, they are not immune to problems. From powdery mildew to bronze foliage and more, it's important to tackle problems as soon as they arise. Look out for these common hedge problems and learn how to treat and prevent them.

Common Hedge Diseases

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Hedges are an excellent addition to any garden, whether you’re looking for extra privacy or want to separate your space into garden rooms. However, it does take some work to maintain, particularly when you encounter any of these common hedge problems. 

While hedges are tough, lack of airflow and harsh conditions can cause issues from powdery mildew to discoloration. Look out for these common problems in your hedges and apply the relevant measures to treat them. 

Powdery Mildew

Close up of a leaf with a white, powdery, mildew coating it.
A lack of proper air flow and moisture can cause this powdery mildew to form on your hedges.

The disease powdery mildew is one of the most common hedge problems, identified by a white powdery coating covering the surface of the leaves. The limited airflow between branches makes dense hedging highly susceptible, particularly in humid climates. 

This fungal disease is more likely in hedges that are stressed due to lack of moisture. Weaker, water-stressed plants become easy targets for disease to settle in. The white coating spreads to more foliage, impacting photosynthesis and weakening the hedge. 

Luckily, powdery mildew is no reason to panic. The condition is relatively easy to prevent and treat. In mild cases, it’s also unlikely to kill your hedge or do any severe damage. 

Treatment

Watering consistently and at the base of your hedge plants is the best way to treat and prevent powdery mildew. This ensures each plant is healthy and, most importantly, not stressed. The soil should be lightly moist but not waterlogged to prevent rot. 

Amending the soil will also improve moisture retention in your hedging. Mix in compost to retain moisture and improve soil structure. Once amended, add a thick layer of organic mulch around the base of your hedge to keep the soil cool and limit evaporation. 

Poor air circulation is a concern for sheltered climbing plants and thick hedging. The best way to treat mildew, in this case, is to prune the most overgrown parts of the plant. Continue pruning to manage airflow and prevent mildew from returning.

Blight

Close up of a dense, green hedge with a patch of brown, diseased leaves.
Early and late blight will manifest in the spring and can be difficult to treat once it’s been infected.

The common disease blight is caused by various fungal strains. When it comes to hedging, and boxwoods in particular, there are two common types to watch out for. These diseases lie dormant in dead leaves and produce spores as temperatures rise in spring.

One form, Calonectria pseudonaviculata (formerly Cylindrocladium buxicola), is identified by a few signs:

  • Spots on leaves
  • Wispy grey fungus growing on the underside of leaves
  • Black staining on woody parts.

Over time, these spots can become larger areas of dead tissue, leading to defoliation.

Another form of blight, Volutella buxiis identified by pink pustules on the undersides of the leaves, black streaks on branches, and quick defoliation. It most often spreads in humid weather. 

Treatment

Copper fungicides have some effect on blight, but the disease is difficult to treat once it sets in. That’s why the best form of treatment is prevention.

As blight remains dormant in dead leaves, the first preventative measure is removing debris around the base of the hedge. Rake up dead leaves and discard them (don’t compost) while also disposing of other affected material like branches.

General care like maintaining soil health and watering correctly (most notably when it comes to blight, not watering too much) also goes a long way towards preventing blight.

Aphids

Close up of the back of a green leaf with tiny, reddish bugs all over it.
Spray your hedges with a strong jet of water several times for a few weeks to help treat an aphid problem.

Aphids are almost impossible to avoid in the garden. Hundreds of species flock to a range of plants, including hedging. In spring, you’ll often see them attacking new green growth or areas where the plant is more vulnerable. 

Aphids typically group together, making them relatively easy to spot when you look closely. Also look out for distorted leaves, discoloration, and general lack of growth. These sap-sucking pests quickly weaken the plant, leading to the common symptoms mentioned. They also spread honeydew which can develop sooty mold over time.

Treatment

For small issues, try spraying an aphid colony with a strong jet of water. It will be difficult to remove all the aphids, particularly in dense hedges, so continue spraying or wiping them off over several weeks to limit reproduction. 

The best way to tackle aphids is by encouraging natural predators like ladybugs. These will manage the colonies for you, helping not only your hedge but the rest of your garden, too. The best way to encourage them is through plantings of alyssum, coreopsis, yarrow, dill, and others.

Stress

Close up of a green, leafy, hedge with yellow patches of leaves.
Yellowing leaves can be the first sign your hedge is stressed.

Discolored foliage, either yellow or bronze, indicates the plant is stressed in some way. There are several possible causes relating to environment and care.

The first possible cause is weather extremes. High winds, hot summers, or heavy frost can cause some hedge species to turn bronze. Planting the right hedge for your region and providing protection where possible can help mitigate these sudden changes. 

Incorrect watering can also cause yellowing foliage, particularly in cases of overwatering. If the ground around your hedge remains waterlogged for long periods, root rot can set in, leading to stress. 

A less common but still possible cause of bronze foliage is high levels of uric acid in the soil from your pets. Stopping animals from using this area will improve soil conditions and prevent further discoloration.

Treatment

The key to treating environmental stress is to amend the condition leading to stress in the first place.

When weather changes occur, there isn’t much to do besides wait for the plant to recover. But in cases where you can control the environment (like watering or soil drainage), the faster you act, the better. 

Prune any areas that are seriously damaged to promote new and healthy growth. Once the cause of the stress is removed, growth should return to normal. 

Final Thoughts

While hedge plants can suffer from several afflictions, most of these common hedge problems are easy to deal with. What’s more, due to their hardiness, hedge plants will almost certainly recover quickly.

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A close-up of aphids infesting a green leaf. The tiny green aphids are voraciously feasting on the leaf, leaving a trail of small holes in their wake. The leaf's surface shows signs of damage caused by the infestation.

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