Should you be concerned about Leylandii fern branches going brown?

Posted on: August 20th, 2015

I recently received a message via my ‘Ask Matt’ page, which said:

“I have a large Leylandii fern tree that split into two trunks years ago. Recently one of the trunks has started to move and the branches are starting to brown and lose colour. I’m concerned that the tree is dying and might fall over onto my neighbour’s fence or shed. Should I be concerned?”

Simply put, yes.

Cuprocyparis (formerly Cupressocyparis) leylandii is a tree that is like Marmite – you either love them or hate them. Leylandii provide exceptional privacy but they grow very quickly and can become very tall if you don’t cut them regularly. In fact, the green species of Leylandii can grow up to 25m high if left unpruned.

If there is a neighbour dispute about a hedge, it’s very likely that the culprit will be a Leylandii. In fact, there have been so many disputes that the ‘high hedge law’ was introduced in 2005, enabling local authorities to intervene and decide on any necessary action required. This could result in a fine of £1,000. This is before you look into the repercussions of damaging your neighbour’s fence or shed (let alone the horrendous possibility of injuring people if your tree was to fall).

Therefore, if there are any issues with your Leylandii, it is important that it is sorted as quickly as possible. Without looking at the offending tree, it is impossible to say for sure what the issue is; however, there are a few possibilities.

Lack of water

You might assume that your trees are well established and can get everything they need from the soil. However, if they have to compete with other plants nearby, your tree may be short of water. Make sure you water well and if you can, mulch the area around the trunk with compost or bark chippings.

Cypress Aphid

Hearing the symptoms, it could be that your Leylandii has been attacked by a cypress aphid. This is a highly destructive insect that sucks the sap out of the leaves. This causes the leaves to turn brown, eventually killing branches and ultimately the entire tree.
Climate change is blamed for the millions of cypress aphids that are now about to survive milder winters. John Buxton, a consultant entomologist described the insect as a “very, very virulent pest.”

“They feed by sucking sap and the plants react by dropping their needles and going brown,” he explained during an outbreak in 2007. “The damage they cause is far more severe than with most aphids. It can’t be reversed.

“You can tell if aphids are present because they leave lots of black sooty moulds from secretions,” he added.

Root disease

A root disease such as honey fungus or Phytophthora is unlikely in this case but it can cause a tree to die completely. Honey fungus is the common name of several types of species of fungi that attack and kill the roots of numerous perennial and woody plants. It spreads underground, killing off the roots of plants and decaying the dead wood.

You can check if a plant is infected with honey fungus by peeling away the bark at the base of the tree to see if there is a paper thin, white layer of fungal tissue.

Phytophthora root rot is another common cause of root and stem base decay. Microscopic, fungus-like organisms cause plants to decay, with symptoms including wilting, sparse foliage and branch dieback.

What next?

There are many pests and diseases that can severely affect a plant’s health, as well as human error. The key is to determine the exact problem as soon as possible and to deal with it before it gets out of hand. Prince Tree Surgery is always on hand to offer advice and conduct a site visit – all you need to do is call.

We hope you found this article on ‘Should you be concerned about Leylandii fern branches going brown?’ useful, if you would like to discuss any aspect of this article then please do not hesitate to call Prince Tree Surgery on 01277 229709