How to deal with sudden tree death

October 9th, 2016
Posted In: Gardening know how

Sudden tree death is a particular tragedy for small and middle-sized gardens. We only have a few trees. And each one is special.

We have a smokebush (Cotinus coggygria ‘Grace’) which has grown to a height and spread of around 7 metres (about 25ft).

Cotinus coggyria 'Grace'

Cotinus coggygria ‘Grace’ in summer 2015. It’s the deep red tree.

Its glorious red foliage is the main focus in the garden, especially in autumn when it changes from glowing copper to burnished gold almost in front of our eyes. It shields us from nearby windows (for more about trees for privacy, see here.)

Dramatic autumn colour

The copper and gold of the autumn cotinus have inspired the rich red theme for our dahlias.

This year has seen a long, cold, wet spring followed by a hot, dry summer. In the middle of August the Cotinus suddenly turned brown on one side. All the leaves off one main branch had died.

Sudden tree death - one half of this small garden tree has suddenly died

One side of the tree has died. This was in August 2016 after a short hot spell. This cotinus is as tall as the silver birch you can just see behind it.

Step one – try Google

I searched for ‘Sudden tree death’ and ‘Cotinus coggygria dieback.’ The specific query was more helpful. Second from top of the page was the RHS advice on Verticillium wilt.

The symptoms matched. There was also a list of other susceptible plants, including elder and rose. Two years ago a black elder and a Rosa ‘Rosarie de la Hay’ both looked dead.

We cut back the black elder and it has since revived. It seemed likely they were both affected by Verticillium wilt.

Other trees have also died in this garden. We thought honey fungus was to blame, although we couldn’t see or smell it. It’s possible that verticillium wilt was the culprit, not honey fungus all along.

Step two – phone a friend (one who knows more than you do)

I consulted Posy Gentles and Matt Jackson, both professional gardeners.

Posy looked at the tree and spotted that all the dead leaves were attached to one branch. She advised cutting it off. She also agreed that the symptoms looked like verticillium wilt.

Cut off the diseased branches

The tree after one main branch was removed. It is about half the size in volume.

The tree looked more graceful, and appeared completely healthy. Phew. A lucky escape.

However, a month later we returned from a long weekend to find leaves browning and curling up in another section of the tree.

Matt Jackson is a garden consultant, and works on large estates (as well as smaller gardens). Some have lots of trees, so he’s accustomed to peering at bark and rootling around roots. ‘But on a large estate, a dying tree either isn’t a problem – we just take it down. Unless it’s a very big problem because it may have a notifiable disease that affects a whole swathe of trees.’

In a middle-sized garden, a dying tree is quite a middle-sized problem because the tree will leave a big hole when it’s gone. And it takes years to grow a tree to seven metres high.

On the other hand, the middle-sized gardener often sees a hole as an opportunity.

Matt recommended that I scrape away a bit of bark to see what was going on underneath. ‘If you can see green, then the tree is probably fundamentally healthy,’ he said.

Scrape a piece of bark to see the marks

These dark stripes could be a sign of a fungal infection, such as verticillium wilt.

I can see green, but I can also see the striations of fungal infection.

Step three – post your sudden tree death on social media.

I posted ‘Has my smoke bush got verticillium wilt?’ on Twitter, along with photographs.

Nobody sniggered. A few people got back to me and said they agreed it was probably likely.

Check the wood for markings

Are these the marks of earlier – non-lethal – infestations of verticillium wilt?

Step four – join the RHS and send a sample

The RHS run a personalised advisory service for members. You can send a sample of material, plus photographs.

I went out to snip some dead leaves off, and also noticed that there were tiny, flea-like insects on the leaves.

It’s all been bundled into a bag and is ready to post. However, if it is verticillium wilt, it’s not treatable and will stay in the soil forever, according to the RHS.

You can also consult the Forestry Commission’s diagnostic and advisory service, Forest Research about sudden tree death. They also take postal samples, but charges apply.

Step five – consult a tree surgeon

The problem is that not all people who call themselves tree surgeons are qualified to diagnose diseases.

The Arboricultural Association has a Find-a-professional service here. However the nearest one to us was around 40 minutes drive away, and that makes visits expensive. Qualified tree surgeons (quite rightly) charge several hundred pounds a day.

They can do things like improve the soil and nutrition around the tree, but it’s not a guaranteed cure. You could spend a few hundred pounds and still lose the tree.

There are lots of people who live nearer and who call themselves ‘tree surgeons.’ Some I would describe as ‘Chain-Saw Man’, whose only aim is to cut trees down. See the difference between arborist, tree surgeon and chain saw man here.

Step six – plan for the worst and hope for the best

We have decided to prune the tree in the winter, and also to plant another tree nearby. It must be one that is resistant to both honey fungus and verticillium wilt. Matt recommends Liquidambar styraciflua, which is resistant to verticillium wilt and rarely attacked by honey fungus.

Cotinus coggygria 'Grace'

The morning sun streaming through the Cotinus – I hope we’ll see this again next year.

We’ll mulch the area. When spring comes we will also look into giving all our trees some extra nutrition.

When pruning a tree back, then always think about the shape. Even if you’re having to cut away dead branches, it’s worth thinking about pruning it for both light and privacy.

How to deal with sudden tree death

This was the cotinus in autumn 2015 – glorious reds and golds instead of dead leaves!

Plant your tree correctly!

The leading cause of sudden tree death is that it wasn’t planted properly in the first place. Planting trees is easy, but there are a few key facts you need to know. See this post for expert advice on how to plant a tree.

Update in 2022…

The following spring the cotinus grew back well. But we had another dry summer, so another chunk died.

We have since slowly cut it back every autumn, bringing it back down to the size of a large shrub rather than a small tree.  The summer of 2021 was relatively wet, and the tree shows no signs of dieback.

So if you think your tree is suffering from verticillium wilt, don’t rush to cut it down. It’s very difficult to get viruses and funghi out of the soil permanently, so your only option is to plant trees and shrubs that don’t suffer from those problems.

Here’s a post on choosing the right tree for your garden. And if you want a tree for garden privacy, see here.

You can see how healthy it looked in 2018 in this post on the best trees for autumn colour.

Cotinus or smokebush

You can see that the cotinus is much more of a shrub. It’s now half the size of the trees around it. But it’s healthy.

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10 comments on "How to deal with sudden tree death"

  1. Anne Harper says:

    Please can we have an update? What happened? I think I may be experiencing Verticillium wilt with my cotinus royal purple.

    1. Will do. We have had to cut the cotinus back twice, but new growth has appeared both times. If you think your tree is getting verticillium wilt, I suggest you cut away the dead branches, but leave the tree to see if it will grow back.

  2. Matt says:

    The November issue of gardens illustrated has some excellent autumn colour tree and shrub options, some of which are very unusual. Page 82

    1. Thank you – I’ve already ordered your Liquidambar suggestion, as it seemed to be one of the few that would (probably) withstand both verticillium wilt and honey fungus, and would have autumn colour.

  3. Joanna says:

    I enjoyed this good-humoured approach to what can be a devastating consequence of tree disease. Over the course of a couple of decades, almost all of the trees in my mother’s middle-sized garden succumbed to honey fungus. Some expert or other told her the only remedy was to remove and replace ALL of the topsoil – not in her budget, nor in many other people’s, I shouldn’t imagine. We haven’t properly explored planting HF-resistant trees in place of those that were lost. It’s a good idea. I wonder if there are many species of tree that will resist HF? I will try and find a list online.

    1. The RHS does lists of trees that are resistant or which rarely suffer from honey fungus and verticillium wilt. As far as I can see, we have no hope of excluding it from our gardens so it’s just a question of keeping going. I think that keeping the trees healthy is helpful.

  4. Anne Lyon says:

    I posted a comment earlier but it doesn’t seem to have shown here, so here goes again. Thanks for your post; exactly the same thing happened to my Cotinus ‘Golden Spirit’ in August and I did the same thing ie removed the offending branch (I thought it was something heat related as it had been so hot). After reading the info on the RHS website and compared the transverse stem damage and the black streaks under the bark, I have concluded that it probably is Verticillium wilt. I have actually removed the whole plant – mine is still a small shrub rather than a tree because the whole thing was affected and more of it was dying. Might seem a bit drastic but I don’t want it to persist. So thank you for your post!!

    1. Probably the best course of action. I am hanging on with our cotinus for just one more year, as it is such an important feature in the garden.

  5. Anne Lyon says:

    Well that is interesting, I am now about to go and check my Cotinus which has also had dead branches in one section this year – initially I thought it might be heat damage and pruned it back but never thought of Verticillium wilt. Closer inspection required, thank you!

    1. I wonder if verticillium wilt is worse this year. I also wonder whether the tree has gone through bad patches before and recovered, as there are marks in the rings, so I am not going to chop it down yet.

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