Quote from Lee Garden Ninja on 3rd November 2025, 9:56 pm

Hi @cee

Many thanks to your kind words about my Youtube channel guides!

Could you please upload a few pictures for me to assist further?

many thanks

Lee

Quote from Cee on 3rd November 2025, 10:56 pm

Here's the tree and a close up of the canker.  The other side of the trunk is ok at the moment. The canker looks awful. 

Quote from Lee Garden Ninja on 4th November 2025, 12:39 pm

Hello @cee

Thanks for the kind words about my YouTube guides!

It's lovely to hear the hedge planting video helped you, and I'm truly sorry to hear about your mum. The fact this Prunus Subhirtella was a gift to her makes it even more precious, and I completely understand why you're so determined to save it. Trees with that kind of history are irreplaceable, and your dedication to helping it through this challenge is admirable.

First things first: please don't beat yourself up about the water sprouts or the Medo sealer. We've all made mistakes in the garden, and cherry trees are notoriously sensitive, as you've discovered. The fact that your tree is still looking glorious in its autumn colours and producing winter blossom is actually a really positive sign. It tells me the tree still has plenty of vigour despite the canker issues on the trunk.

Understanding the canker situation

You're absolutely right that conventional wisdom says no pruning or cutting on stone fruits during autumn and winter. This is because wound healing is poor during dormancy, and wet conditions create the perfect environment for bacterial and fungal infections to spread.

However, your situation is a bit more nuanced because you're dealing with existing cankers that are already compromised, and you're in the wet southwest on clay soil, which, as you rightly point out, is exactly the wrong combination for cherry tree health.

The cankers expanding after heavy September rain are typical behaviour. The pathogens that cause these issues (usually bacterial canker or a fungal infection) thrive in wet conditions, and autumn rainfall essentially reactivates them after summer dormancy. The fact that they've become "really horrible" recently suggests the infection is active and probably will continue to worsen through winter if left completely untreated.

My practical advice for getting through winter

Here's what I'd suggest, and this is based on experience with similar situations where doing nothing felt riskier than doing something carefully:

I would not attempt to cut out the diseased wood until late winter or early spring (February through April is the traditional window for Prunus surgery). However, I do think there's merit in protecting those cankers from winter wet, which is clearly your main concern. Your instinct about creating a barrier isn't wrong, but I'd approach it slightly differently than your proposed Bordeaux paste method.

What I'd do instead is carefully clean around the canker margins with a stiff brush to remove any loose, dead bark and debris where moisture and pathogens can harbour. Then, rather than packing the sunken areas with paste, I'd then leave the wound without any paint or treatment, which is how I rtreated my Damson which the previous homeowner had taped.

The problem with gaffer tape is that it can trap moisture underneath, causing the canker to sweat. Consider using breathable wound tape or even strips of hessian secured with garden twine if you must wrap it, though I wouldn't. The goal is to keep direct rainfall off whilst allowing some air circulation.

Supporting the tree's overall health

The work you've already done is spot on. Clearing debris from around the base reduces disease pressure, and the blood, fish and bone will support root health going into winter. Clay soil is challenging because it holds moisture, which cherries detest. If you haven't already, consider these additional steps:

• Improve drainage around the root zone by incorporating horticultural grit or sharp sand into the top few inches of soil in a circle around the tree (not right against the trunk, but from about 30cm out to the drip line)
• Keep the area around the trunk clear of mulch, leaves and vegetation through winter to promote air circulation and reduce humidity at the base
• Monitor for waterlogging after heavy rain and consider creating very gentle surface channels to guide water away from the trunk if pooling occurs

The spring treatment plan

Come late winter (late February onwards), when the weather is drier and the tree is just starting to wake up, that's when I'd consider surgical intervention. At that point, you can carefully excise the worst of the dead, cankered tissue back to healthy wood using a sharp, sterilised knife.

The key is to create a clean wound with sloping edges that won't collect water, and then LEAVE IT ALONE. I never treat or paint such wounds any more.

The witches' brooms you mentioned are interesting and might be related to the same stress factors causing the cankers, or they could be a separate viral issue. Keep an eye on them, but they're generally less critical than the trunk integrity.

Being realistic about the prognosis

I want to be honest with you: cankers that encompass half the trunk are serious, and there's a real possibility the tree may not recover fully even with treatment. However, the fact it's still flowering, leafing well and looks healthy in the crown suggests it's a fighter. Cherry trees can be remarkably resilient when they want to be, and yours clearly has strong sentimental reasons to keep going! Like I said I've saved countless Damsons this way.

Your goal through winter is simply to minimise further deterioration and support the tree's natural defences. Come spring, with proper intervention and continued care, you may well be able to stabilise the situation and give this precious tree many more years.

Further reading and support

I've written several articles and the forum has some brilliant discussions that might help you through this situation. Here are some specific resources that are directly relevant to your Prunus problems:

Forum discussions on similar cherry tree issues:

• Tree Canker Advice: Sickly cherry tree covers exactly the kind of canker problems you're experiencing and treatment options
• Sweet Cherry Tree: Splitting trunk discusses trunk damage and canker management with some excellent practical advice
• Ornamental Cherry Pruning explains why we never prune cherries in winter due to silver leaf disease
• Fruit Tree Pruning for Cherries has comprehensive guidance on the correct timing and techniques for Prunus species

Articles on soil improvement and drainage:

• Plants That Love Clay Soil has excellent information on managing clay soil drainage issues
• How to Improve Soil from New Build Houses discusses improving heavy, waterlogged clay soils
• Soil Types Explained helps you understand your soil and how to work with it rather than against it

General fruit tree care:

• How to Prune an Apple Tree whilst focused on apples, contains excellent general principles about wound healing and the importance of timing

Keep us posted on how your tree does through winter, and don't hesitate to share updates on the forum. We're all rooting for you and your mum's tree. If you've found my advice helpful, I'm always grateful for a Google review to say thanks!

https://g.page/gardenninja/review?gm

 

Best of luck, Cee!

Quote from Cee on 4th November 2025, 5:42 pm

Wow Lee what a super helpful, detailed response. Thank you so, so much. I was despairing at the lack of information about winters. 

I think you are right and I have to hold off the 'surgery' until we hit a dry patch after February - I don't want to make things worse. I know it's a critical situation for my tree so I will put my new pruning knife away for now.  But what you have explained has really helped me to think some more about protecting the damaged parts of the trunk through our soggy winter. 

I hear you about the gaffer tape and preventing air circulation - like a human wound it's got to 'breathe'. I questioned it when our local garden nursery plant man suggested it.  I did think of grafting tape but people say it's very hard to use for beginners.

My latest, (probably mad), idea is to make a little temporary roof out of something like a plastic cone recovery collar for dogs  just to keep the worst of the rain off and channel it away. If I can attach it to the tree above the cankers but a few inches above the ground the air can easily circulate. I'm thinking I can use self-fusing silicone tape to help affix it to the tree (I read about the tape this morning in a fruit growers forum - it's waterproof but won't damage the bark when you remove it). Or I could even run a silicone seal bead around the top (like around a bath but transparent) - that's also water proof but will not hurt the tree and will be easy to remove in the future. 

The tricky bit is going to be getting a collar to stay attached to the tree, I guess. I'm not a dog owner so I'll have to buy one and improvise.  We'll see - it may need a re-think but you've inspired me to think some more beyond the basic 'drastic surgery right now' or not dichotomy. 

Thank you also for the clay soil links. It's red, squidgy and messy, I really need to work with it.  I will follow your advice for this winter and making sure it doesn't get too soggy near the tree.  

You really have given me so much to think about - your response to my question is like a masterclass. Thank you again. 

I hope others find this useful going forward - what to do with Prunus cankers in winter is definitely a gap in the online knowledge base. I will update this thread as things develop, I think that's important. I'm going to be watching my tree and on tenterhooks all winter.  ??