My 7ft hedge looks like it is dying in a central part. The hedge on either side is strong and healthy. Is there a way to recover it or fill the space with new hedging? Brian McGuinness, Dublin
Partial dieback in a mature hedge is not uncommon and is both unsightly and frustrating to manage. There are multiple possible causes, from a variety of pests and plant diseases, drought and waterlogging, to mechanical damage to the plant including severe compaction of its root system.
It’s hard to make out the variety of hedge from the photo you supplied, but it’s worth noting that certain kinds are vulnerable to specific pests and diseases that will cause them to die back. Examples include box hedging (Buxus), which is vulnerable to box blight as well as box caterpillar, both of which cause dieback and discolouration of the foliage if left untreated. Privet hedging, meanwhile, is particularly vulnerable to honey fungus, an untreatable disease requiring swift removal of all parts of the afflicted plant. Symptoms here include dieback and browning of leaves, as well as white fungal growth and honey-coloured mushrooms around the base of the plant.
To gauge how sick your hedge is, scratch away a small section of the outer layer of a selection of the affected branches with your fingernail, working slowly down the plant. If the branches reveal green living plant tissue, that’s a good sign. If they reveal just pale grey-brown woody tissue, this indicates the branch is dead.
RM Block
Next, use a clean, sharp secateurs to cut away any dead branches right back down to healthy growth. There’s a good chance that the root system of the affected plant will still be strong enough to eventually generate new healthy branches, although this will take time.
Bear in mind that hedges are naturally hungry for nutrients and so the soil can become very depleted over the years, especially with a mature hedge. To help yours recover, gently remove the top 5cm-7.5cm layer of soil around the base of the plant and replace it with a good quality top soil. Next spring, spread mulch and sprinkle some handfuls of a good-quality slow-release organic pelleted fertiliser along the base of the hedge to help stimulate new growth.
If your hedge still doesn’t recover, then unfortunately it suggests that the affected plant is dead. Digging out its root system and replacing it with a young plant would be a very challenging task, which I’d try to avoid (the exception being if it has honey fungus). Instead try selectively pruning some branches on either side of the gap to encourage new growth. Use some string to gently train these young branches to grow in a horizontal fashion, which over time should slowly but surely fill the gap.
