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Sweet Cherry Tree: Splitting trunk is it canker?

#1 · 1st August 2024, 7:03 am

Hi,

I planted this tree back in 2010, and it did very well for years. It is a Prunus avium 'Hedelfinger Riesenkirsche'.

In 2017, I had to go abroad, and returned this spring to find it in a very sorry state. The tree is covered in lichen (both gray and green), and has one massive wound just above its graft union, and another one slightly further up. I'm very concerned about these "wounds". The tree had a coated chickenwire guard around it to prevent cats from using it as a scratching post, so it can't be animals. The weeds around the tree were up to its first branch, and ants had a field day during fruiting, bringing aphids to the crop.

It's clearly very unhappy; it has few leaves on long, thin spindly branches. The cherry crop was paltry; the cherries weren't palatable; and around 50% had some horrible fungus problem.

I've patiently waited until this week to prune it, and have just completed a tentative first pass - I'll do some more major cuts in late August, those long skinny leaders need reduction. I'm not sure what to do about the long spindly branches - should these be brutally cut back by, say, 1/3rd? Is there any way to encourage new leaves along those bare branches?

I've been drenching the tree in TLC, compost and compost tea.

Any advice would be much appreciated.

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#2 · 1st August 2024, 2:34 pm

Quote from Lee Garden Ninja on 1st August 2024, 2:34 pm
Hi @zuff
Thanks for the question and pictures about your ill Cherry tree. It certainly doesn't look healthy or like its thriving.
The first thing I notice is those splits on the trunk are far too uniform to be a tear causes by frost or canker. Cankers usually are a secondary infection that capitalise on poor cuts, wet conditions or tears in the tree. I know you said it was surrounded by chicken wire but I think these cuts are made by someone, whether by accident with a trimmer or tool of some kind. Especially looking at the positioning of them directly above each other.
The good news is the foliage looks healthy and fruit trees are incredibly resistant to recovery. Giving it a compost tea drench is a good ideal. I would prune this hardback by up 1/2 to help encourage side growth and boost its vigour.
Cherry trees can experience bark splitting due to several factors which I'll detail below for other Ninjas who search this query, often related to environmental conditions, canker like you mentioned from poor pruning cuts and other tree health issues. Here are the main causes:
Frost Cracking: Sudden temperature changes, particularly in late winter and early spring, can cause the bark to contract and expand rapidly. This thermal stress can lead to vertical splits in the bark, commonly referred to as frost cracking or sunscald.
Sunscald: In winter, the sun's warmth can heat up the bark on the south or southwest side of the tree during the day, followed by rapid cooling at night. This temperature fluctuation can cause the bark to split.
Rapid Growth: Young cherry trees or trees that have been fertilized heavily can grow quickly. Rapid growth can sometimes cause the bark to split because it cannot expand as fast as the tree grows.
Mechanical Injury: Damage from lawnmowers, trimmers, or physical impacts can cause bark to split. Once the bark is damaged, it becomes more susceptible to further splitting from environmental factors.
Drought Stress: Extended periods of drought can weaken the tree, making the bark more prone to splitting. Conversely, a sudden increase in water after a drought can cause rapid growth that the bark cannot accommodate.
Pest Infestation: Borer insects and other pests can weaken the bark and underlying wood, making it more prone to splitting.
Disease: Certain diseases, such as canker infections, can cause the bark to crack and split as the disease progresses. Usually this is followed by an oozing or secretion which is why I don't think your tree has true canker, unless its been cleaned up?
https://youtu.be/EWPEuJ48kmU
My pruning guide here may help other Ninjas avoid canker and other infections, such as bacteria from poorly healed pruning cuts. Do let us know how you get on.
All the best
Lee Garden Ninja

Hi @zuff

Thanks for the question and pictures about your ill Cherry tree. It certainly doesn't look healthy or like its thriving.

The first thing I notice is those splits on the trunk are far too uniform to be a tear causes by frost or canker. Cankers usually are a secondary infection that capitalise on poor cuts, wet conditions or tears in the tree. I know you said it was surrounded by chicken wire but I think these cuts are made by someone, whether by accident with a trimmer or tool of some kind. Especially looking at the positioning of them directly above each other.

The good news is the foliage looks healthy and fruit trees are incredibly resistant to recovery. Giving it a compost tea drench is a good ideal. I would prune this hardback by up 1/2 to help encourage side growth and boost its vigour.

Cherry trees can experience bark splitting due to several factors which I'll detail below for other Ninjas who search this query, often related to environmental conditions, canker like you mentioned from poor pruning cuts and other tree health issues. Here are the main causes:

Frost Cracking: Sudden temperature changes, particularly in late winter and early spring, can cause the bark to contract and expand rapidly. This thermal stress can lead to vertical splits in the bark, commonly referred to as frost cracking or sunscald.
Sunscald: In winter, the sun's warmth can heat up the bark on the south or southwest side of the tree during the day, followed by rapid cooling at night. This temperature fluctuation can cause the bark to split.
Rapid Growth: Young cherry trees or trees that have been fertilized heavily can grow quickly. Rapid growth can sometimes cause the bark to split because it cannot expand as fast as the tree grows.
Mechanical Injury: Damage from lawnmowers, trimmers, or physical impacts can cause bark to split. Once the bark is damaged, it becomes more susceptible to further splitting from environmental factors.
Drought Stress: Extended periods of drought can weaken the tree, making the bark more prone to splitting. Conversely, a sudden increase in water after a drought can cause rapid growth that the bark cannot accommodate.
Pest Infestation: Borer insects and other pests can weaken the bark and underlying wood, making it more prone to splitting.
Disease: Certain diseases, such as canker infections, can cause the bark to crack and split as the disease progresses. Usually this is followed by an oozing or secretion which is why I don't think your tree has true canker, unless its been cleaned up?

My pruning guide here may help other Ninjas avoid canker and other infections, such as bacteria from poorly healed pruning cuts. Do let us know how you get on.

All the best

Lee Garden Ninja

#3 · 1st August 2024, 3:02 pm

Many thanks for your incredibly fast reply.

Canker: I haven't touched the wounds at all, no cleaning up whatsoever. I've been concentrating on keeping them open to sunlight and air in the hope that the tree would heal itself by growing new bark over the top. Hadn't thought about mechanical damage due to the chicken wire, but now you mention it, it does look very much like that's the case. I should have inspected the wire for damage b4 binning it but it was so choked w/weeds I just cut it all out and tossed it.

Prune by up to 50%: I hear and obey, great to have emotional support when thinking about drastic measures.

I was wondering if the lichen growth and poor leaf cover might be due to lack of air movement; the tree is pretty much surrounded by buildings and/or tall hedges and walls. Web searches all seem to say "don't worry, lichen doesn't harm the tree", which isn't helpful. The tree gets full sunlight from dawn till around 6pm (in summer).

Here in southern Germany, we get *all* the issues you describe (sigh). Winters can be -12C; Summers regularly bring ~35C. Rain tends to come in bucketfuls or not at all for weeks - but I do have a watering system set up. My only serious pests are aphids, thanks to the ants, but am trying to encourage the birds by hanging feeders in the tree at the appropriate times. However, the wretched things seem to much prefer flinging the contents of my 3 compost bins around 🙁

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#4 · 3rd August 2024, 9:50 am

No worries and glad the replies helpful in Deutschland! 🇩🇪

Honestly, don’t worry about Lichen. It’s actually a sign of a very healthy garden and ecosystem. Trust me when I say the pruning is your best bet for recovery. Remember: pruning invigorates and directs growth. It doesn’t simply reduce the trees growth. It promotes it.

Also cherrys don’t mind part shade either.

Let us know how you get on

Tschüss!