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Dieback on Leyland cypress hedges

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Posted: Monday 13 February 2012
by James Alexander-Sinclair

[...] I have noticed some very sinister goings on: something is disfiguring leylandii hedges with brown patches.

Foliage of brown leylandii hedge

Before we start I should warn you that this post is a little gloomy. While pootling around the countryside seeing clients and such I have noticed some very sinister goings on: something is disfiguring leylandii hedges with brown patches.

Now, to many people this would be cause for jubilation. Something killing off leylandii? Marvellous, no longer do we have to read stories of neighbours falling out. Nor do we have to be bothered with clipping the things so frequently. But in their defence, there are some places where a leylandii hedge is just the ticket, and, if kept neatly clipped and under control leylandii trees can be a fine way to make a windbreak or a high boundary marker.

Interestingly, the original Leyland cypress was an accidental cross between two North American conifers, Monterey Cypress (Cupressus macrocarpa) and Nootka Cypress (Chamaecyparis nootkatensis / Xanthocyparis nootkatensis). In the wild the two trees would never have met, but they did in 1888 in the grounds of Leighton Hall, Powys. The result was named after the owner of the estate, Christopher Leyland. If left alone a Leyland cypress will grow to about 35m, which is beyond even the tallest stepladder!

Anyway, the brown patches: there are a number of explanations. It could be aphid damage. (Cypress aphids are busy chaps, sucking the sap out of the trees - although it is difficult to catch them at it because the brown patches develop long after the damage is done and the aphids have fled.) Or it could be a couple of fungal diseases (for example Pestalotiopsis or Seiridium cardinale). It may even be something as simple as trimming at the wrong time (for example during autumn or when the weather’s hot) or bad growing conditions (wet ground or cold winds).

In short, the brown patches could be caused by a number of things and, I’m afraid there is not much that can be done. Sorry. Unlike some other evergreen hedges, such as yew, holly or privet, leylandii will not re-grow if you cut into old wood, so the only solution is to tie in nearby healthy shoots to conceal any empty patches and wait. A general fertiliser around March and a good mulch would help as well; a healthy plant is much better at shrugging off disease.

All in all, not terribly good news for leylandii hedge owners. If your hedge is badly affected then it may be time to be very brave and dig the whole thing out and start again. This is a very scary proposition, but it’s better than living on with a deteriorating hedge.

The sooner you replant, the sooner the new hedge will grow.

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Talkback: Dieback on Leyland cypress hedges
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david spikes 13/02/2012 at 21:52

it looks like improper trimming or it could be spider mites if they are the soft evergreen curse in the uk that thet are in nev.

Sue Beesley 14/02/2012 at 17:31

Yippee if you have to dig it out (OK it's hard work, but it's a marvellous work out and cheaper than the gym membership). Other than hiding the neighbours, this plant doesn't have much to recommend it.

If you do replant, I'd replace it with Western Red Cedar (Thuja plicata). Does exactly the same job, but a slightly slower growth rate. It can be cut back into old wood and will re-shoot, and it's a nicer, brighter green. Finally, it smells fruity so cutting them is a pleasure...

Emma Crawforth 15/02/2012 at 14:23

I would like to recommend the Leyland Cypress as a tree, if you have an enormous garden. At Bedgebury Pinetum, which everyone who has any time for conifers should visit, they have a whole avenue of them. It is magnificent.

Emma.

gardenersworld.com team

www.alittlesliceofeden.blogspot.com 18/02/2012 at 17:50

The climate is changing and we are travelling. Scary how we now see the impacts around us in such weird ways, but the reality is that every time we travel there is a chance that a fungus or a mould spore or perhaps a Colorado beetle will be travelling with us.

Now that the winters are wetter - or should that be drier - and the summers are hotter (or colder?) our trees and shrubs are getting stressed and that makes them much much more susceptible to whatever little beastie has recently come to visit.

None of this is good news but Natural England decided that the best way to combat climate change is to concentrate on decent biodiversity and resilience - which for gardeners means growing from seeds rather than always clones, and looking after the soil.

I definitely do the latter, but how many of us grow trees from seeds? No wonder Leylandiis are susceptible. There is just one type and no diversity at all.

Once a disease has breached its defences a modern hedge is just a free lunch, so perhaps if a new hedge is to be started it it would be better to start from hips and haws?

James Kelly2 08/05/2012 at 10:26

Hi, I planted 10 leylanndi trees a month ago, some of the tops and shoots have gone brown ! Are they dying? They were planted in good soil with a mix of compost and have been watered in, it has also been raining a lot. Help and advise please. James.