Wednesday, 13 November 2013

I have honey fungus in my garden and am unconcerned




Armillaria mellea, Honey fungus, bootlace fungus. These three names describe the fungus that bring a shudder of fear to most gardeners. To read the gardening press honey fungus is the kiss of death to a garden! The story goes that black rootlike, shoelace-like, fungus strands invade the whole garden from dead tree stumps roots as they spread to new hosts. It is true, it does spread that way as it insinuates it’s way through the soil. But I consider that in most gardens armillaria does very little harm.
There are some significant exceptions and many gardeners will say I am very complacent!

My oenothera is being strangled


Girdled with black rhizomorphs
I am grateful to former student and landscape designer Davy Blakemore who spotted  fungus fructifications on the stump of a dead tree in my garden. I was lifting some plants for him and we found this fantastic example of a seemingly strangulated oenothera garlanded with a beautiful necklace of the toadstool spore-fruiting body. I could sense Davy draw his breath and noticed the look of fear in his eyes. Dare he refuse the plants that his former tutor was giving him? Clearly he had not attended my lectures!

I was thrilled to find this rare example of a plant in the process of being invaded. The next morning I rushed down the road to show it to plant biologist Peter Williams. Like a good scientist he suggested we wash it to examine it more clearly, and then to dissect it. He immediately set to work with his scalpel. Anticipating the likely controversial line in my blog I casually observed that the infected oenothera looked healthy and vigorous. Could it be that rather than being a harmful fungus invasion, that it was a developing mycorrhizal association? Peter is an expert on mycorrhiza and quickly dismissed my suggestion  He is too nice to be rude and after consideration explained why this was a rather silly idea.

Black bootlace has emerged from the ground




Case study 1. My first experience of armillaria

Forty five years ago when we moved into our new house in Bolton Percy we called our home Betula and planted a Young’s Weeping Birch! The house adjacent was called Corylus. Much subtler as the family name was Hazel! The house across the narrow country lane was called Ashdown. The relevant ash was in my new garden, it had been cut back to a huge five foot bore stump. It was the start of my lifetime experience of cutting down trees as close to the ground as one could go without damaging a chainsaw, but not wasting energy digging  them out or hiring a stump grinder. I resolved to make the stump an attractive garden feature by covering it with clematis and other scrambling plants. I suppose it was the  start of my mingle-mangling! I feared the stump might eventually get honey fungus.
And sure enough after five years I saw the first fructifications on the tree stump and very soon later armillaria toadstools appeared in my lawn. Not being confident of my identification - I still fear to eat a wild common mushroom - I took it to college. My botanist friend Mike Ashford walked into my office, declared “nothing wrong with that” and took it home and ate it. Apparently armillaria fructifications taste quite delicious.
An so the saga started. Bootlaces threaded everywhere. I was already a no dig gardener and rarely encountered the fungal rhizomorphs but they were to be discovered up to forty yards away from the stump. When Tim and Ben were toddlers we took up our plastic lined pond and converted to a more childproof bog garden. The underside of the plastic was covered with a beautiful matrix of grasping fingers. They looked rather like the tentacles of a Doctor Who monster clawing to emerge from a subterranean grave!

This acacia was killed in 2010 by the cold. I cut it to the ground and for no good reason it was covered with soil. When I removed the soil it exposed these invading ‘claws’ 

The point of my story is that in the next twenty years I never lost a plant. I did joke that perhaps I lost a flag iris and having seen the top picture I can now envisage it’s demise! I rationalized my experience by concluding that plant death is often a syndrome; a combination of susceptible plant species, plant age, soil conditions - especially  drought and poor drainage - and the actual pathogen. Further research - we could not google then - suggested that there might be more virulent strains.



Case study 2. No plant harmed by the fungus, killed by a bureaucrat’s pen.
Chestnut avenue was a beautiful track lined by sixty magnificent old trees. A new road was to be constructed in our village of Bolton Percy.There were two alternative routes.The crux of the affair and close to the heart of the whole village community, was whether Chestnut Avenue was to be widened with the necessary demise of the trees. It was due to go to court where the result would be decided in a typical British way.
One hired ‘expert’ found strands of armillaria. The trees were doomed! Such is the reputation of honey fungus, the case never came forward and the trees were felled. Dammit, where-ever there are old trees there will be signs of armillaria. Old trees and armillaria go together like chalk and cheese. The fungus was doing no significant harm. The trees were good for another sixty years. What a shame.

Somebody found black bootlaces

Case study 3. Very real damage
We were on a student tour and visited a famous parkland in Cheshire. It had a very fine grove of ancient one hundred year old rhododendrons. The whole avenue was gradually dying, killed by armillaria. The manager was beside himself. He cursed and feared armillaria with very good reason.
Some plants such as rhododendron, lilac and privet are particularly susceptible to honey fungus when they are very old. Honey fungus will gain some kind of ascendency over the years when soil conditions are bad. Often poor drainage will create bad aeration and root death. Dead roots and woody organic material sustain the fungus and the death of deep roots  make the effects of periods of drought more severe. It’s wet enough in Cheshire at the best of times and some of their soils are heavy. It had been a particularly wet season. Who knows it might have been a particularly virulent fungus strain? 
I would argue that it is rare and very real events such as this one that gives rise to the fearsome reputation of this normally ubiquitous and often insignificant fungus.

Case study 4. A new on-going case
So my old friend has returned at the top of my new garden. It must have been with me unnoticed for a few years now, growing from the stumps of any of a dozen cut back trees. All my plants in the infected part of my garden (bar one) are healthy. I have also discovered black fungus rhizomorphs next door in Cathi’s garden where I am in the process of replanting. Sorry Cathi I have not yet broken the alarming news to you that your soil is a seething mass of black bootlaces but I assure you that you have  nothing to fear. 

There are a lot of dead tree stumps in Cathi’s garden

Hot off the press, now that I am suddenly recognizant of this invader I have noticed another dead stump emitting the characteristic melliferous smell at the bottom of my garden!
Now I have found armillaria invading my garden I must look again at a rather tired looking old lilac, a known susceptible genus. For some years now I have pondered it’s removal. Perhaps I should start to panic, another susceptible species, an old flowering cherry is just a few boot steps away!  It is extremely healthy. Over the last twelve years I have established about seventy  different uncommon trees in my garden. Can I be certain that in another ten years they will  still be there?

You can see that I have already in effect written off this lilac by allowing ivy to invade. 
Am I being too complacent?

No, not in my own garden, but yes in terms of being a worldwide problem. I would have liked to merely report that armillaria is a force for good in nature’s carbon cycle and a desirable mycorrhizal host for certain wild orchids and other rare plants. Unfortunately I cannot deny in certain sectors of forestry and orchard production it is a significant scurge. You can see on the net sections of hillsides where hundreds of tree have been killed by this fungus. Large financial resources have been invested in investigating it’s control. Some areas of land are infected with huge bio-masses of infective fungal rhizomorphs. In some cases they are hundreds or even thousands of years old, repeatedly refreshed by new generations of trees. Some of these biomasses are genetically identical, in effect a huge monster.

Armillaria mellea and it’s many relatives - there are at least seven British species, not to mention individual strains - can be a real problem.
It’s just that I want to suggest the world is a very big place and that there are millions of acres including your own garden, where the fungus  will be present and need not be a cause for concern.

 More armillaria

 Armillaria bootlaces have been likened to fibre optic cables of parallel strands of fungus hypha

Photographed on our recent Tyne walk, Amonita the fly agric fungus has a symbiotic relationship with birch 
Photographed on our recent Tyne walk, Amonita the fly agric fungus has a symbiotic relationship with birch 

Can anyone tell me if this is the Turkey Tail bracket  fungus growing on a cut back birch in Bolton Percy churchyard?




30 comments:

  1. I don't know very much about honey fungus, or I didn't before reading your post. Amazing to see how that nemophila is being strangled. I hope your lilac and cherry don't succumb, it would be such a shame.

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    1. Thanks for the good wishes Jo. The cherry is the well known variety Kanzan and when we moved in twelve years ago it was severely overgrown with 5 trunks! I t is now whittled down to one trunk and is a very fine tree, It is very healthy and I have no fears for it. I am prepared to write off the lilac if necessary but after sounding off about it in this post I had better leave it to report back! It does have a strong new growth coming from the ground and as I believe it is on its own root and is not grafted it might well be my future tree!
      I want to thank you for inadvertently bringing to my attention my typo of calling it nemophila! It's oenothera, not biennis the common one, but a variety that self seeds and comes in yellow, orange or pink

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    2. ps I have changed it to oenothera on the photo!

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  2. Honey fungus is a topic that comes up regularly on various gardening forums and the replies must send shivers down the spines of those who asked the question. I know nothing of honey fungus and based purely on what I've previously read tend to ignore any fungus I find growing in the garden. I tend to prefer the 'ignorance is bliss' approach - I worry enough that plants will thrive without adding another reason that they might not.
    I enjoyed this post Roger and I do hope Cathi is as open minded as you.

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    1. A good attitude Angie, many things in gardening are overhyped. I have a post ready for a couple of weeks time on Russian vine!
      I suggest you enjoy all the interesting ecology in your garden and I was delighted in my research to find there are some plants such as a rare orchid which derive sustenance from honey fungus.

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  3. Must admit I always dreaded honey fungus appearing so your post is some comfort. As for eating foraged fungi - no way would I risk it!

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    1. Nor me but I am assured that some are delicious.

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  4. Another fascinating post, Roger. You ought to call youself not the "No-dig Gardener", but the "Myth-busting Blogger"!

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    1. Oh no the no dig is my passion Mark, but just wait for what I have to say about the Russian vine next month!

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    2. I know you are being jovial Mark but I don't think armillaria is a myth but just grossly over-rated and over feared. From my point of view if I lose my lilac amongst thousands of other healthy plants it's just a planting opportunity or even of ecological interest when I observe wether or not its sucker makes a new tree!
      I think there is a blame culture in gardening, one about which I will future post. It's about gardeners needing a scapegoat for their gardening losses. Things like armillaria and weedkillers often get the blame when they are completely innocent!
      I wrote about shrub death in my recent post, Why has my shrub died?
      As to myths if any passing reader wants to know about my myths they should just pop myth into my search box! (promotion over)

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  5. Power of the press Roger, plus a blame culture in general not just in gardening. I have fly agric round by birch trees and look forward to their emergence every year. Your fungus looks like Trametes versicolor, the Turkey Tail bracket fungus, although, I would have expected it to be browner in colour, I am no expert but it is the most common of its type.

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    1. Thanks for the confirmation Rick. I think it was white because it was very fresh fungal growth. I was at Bolton Percy this week and it now looks much browner

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  6. I am opposed generally to having a knee-jerk reaction and killing things off. It seems to me that we do too much killing, and not enough waiting and seeing, or work-arounds, so I enjoyed your post. although I don't think I would want to try eating the fungus!

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    1. yes I agree it is best to watch before making decisions. I might have created myself an image of always spraying glyphosate but other than this I rarely do anything about pest and disease other than sometimes squash them!
      And no, the toadstools don't look very appetising to me either- I do think they actually look very attractive but not to eat.

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  7. A very interesting post and very comforting. My garden was an old orchard and we had to cut down six dead cherry and apple trees. It is so expensive to hire a stump grinder. Roses have also died and I learnt that they are the same family as apple trees so susceptible. I have been too worried to replant any trees as the fungus comes up all over the lawn no doubt feeding off old roots. Anyway you have reassured me that as long as I look after new plantings and keep them well fed and watered maybe I will get away with it. Thank you. By the way is it true that the fungus glows in the dark?
    Chloris.

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    1. A few very interesting points Chloris (or is that about glowing in the dark- the word for the phenomenon when the fungus glows is very similar, if my BTbroadband was better-it has been hell today, I would look it up)
      Best of luck with your new trees, just to be on the safe side don't plant susceptible ones, although I would certainly risk apples.
      I think you have got your wires a little crossed ( or should I say laces?) with the apples. Because your dead trees were apples does not does not in any way mean that the armillaria will particularly attack apples and even less so other members of the apple family. Apple replant disease is perhaps what you are thinking of and that is overrated too- just don't plant very close to the old stumps.
      As to your comment about the Jack'O Lantern phenomenon of glowing, yes any part of the fungus glows but it needs pitch black to see it. In the trenches of WW1 the fungus pieces were used as a marker. I have never seen it myself but I think I will go out now (wearing my dressing down) to have a look. You will know from my post that I should expect to find some!

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  8. Did you see this week's Gardeners World? Monty Don mentioned honey fungus!

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    1. No, I am not really fan of gardening tv! I don't have a direct line to the great man.
      But I have joined the Gardeners World website this weekend and intend to start making comments.

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  9. Hi Roger
    You've somewhat cheered me. 4 years ago we moved into a garden that had been an orchard. This Spring a beautiful twisted willow didn't come into leaf and was confirmed dead by the dreaded HF by the RHS team. We felled this but a Sorbus ( planted 2 year ago) also died. I now have an apple tree nearby that is looking ill ( after the most wonderful crop of apples) and has sprouted lots of toadstools. I blame all the old stumps in the garden and the very wet summer in 2012 when it was almost waterlogged at times. We just live in hope as I have a 2 year old pergola planted with roses nearby. I can't dig the old stumps out ( and anyway believe this might disturb things and make it worse!). We're resigned to losing more.

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    1. Hello anon
      I am surprised my article cheered you, I would have thought with all your problems you would be banging the table (as I would) and tell me what a complacent idiot I am!
      Some sites can be much more of a problem than others and it sounds that in addition to ample sources of the pathogen from the stumps you have a drainage problem.
      You will find me more often advising "You have a drainage problem or a drought problem" than saying 'your plant has been killed by pathogen x, y or z. At the moment I have a a cut leaf maple in a tub showing coral spot. I am not saying the coral spot is killing my shrub, I am saying "what have I done wrong for my plant to get coral spot?"
      sorry I can be a bit wordy!

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  10. Hi,I have a 2 acre woodland garden jam packed with magnolias,rhoda's,acers etc.All the nice stuff.
    I also have honey fungus everywhere,you eventually learn to live with it,you loose good stuff,and other stuff fights it off or even bounces back.The plants near bamboo thrive and are allways unscathed.There are always surprises,however,honey fungus has taken out my three oldest,biggest asparagus plants this year.About 12 years old.Lots of h.f. observations and stories over the years.

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    1. You seem to have more problems than me Rhoda but I like your philosophical attitude and no doubt you derive much interest from your fungus. I would love to hear some of your stories, feel free to share them.

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    2. just checking to see if this posts

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    3. yes it has Rhoda, look forward to hearing from you!

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  11. Hi,I've tried to reply several times and lost everything.One more time.
    I have got interested in Honey Fungus,out of necessity and the lack of information.I have been gardening here for 17 years.The garden has many soil types and is on old farmland, that was ancient woodland.Gets very wet,but dries out quickly and has many old stumps,hence Honey Fungus.I have lost maybe 30 shrubs /trees out of maybe two thousand,so it is not as bad as the media make out .It only really becomes a problem when you lose a favorite or 3/4 plants together,leaving a gap.
    The garden is now woodland,covered in leaf litter and is left to fend for itself.This it what I've found out through trial and error..I don't strim around plants,as any wounds will let our friend in, as will root rock and weeding.I use roundup ,which kills most weeds and grass and incourages moss,good tip for japanese style gardens.Honey Fungus loves plastic sheeting,weed supressing mats,old carpets etc,and these should be avoided at all costs.Stressed plants will be prime targets..When I replant,I use bamboo,enkianthus and magnolia,these seem to be imune or chase the fungus away.When I have an ailing plant,I feed, and scatter wood ash around the base,this seems to work most of the time.The fungus is indiscriminate,it will follow a tree root, taking out two rhododendrons of the same variety,only to leave a third,and you can plant in an infected stump only to see the plant thrive.It seems to weaken plants at ten years or so and they will fight it off and recover.Some will succumb no matter what you do.I don't think the usual tar oil remedy works and when used as a preventative has failed miserably,it is also expensive and so totally useless for a large garden.Japanese maples take a hammering but my best is growing in an infected stump.The asparagus plants I previously mentioned were in a tunnel,so the fungus also likes hot and dry.I propagate and hybrdize many plants,so am always trying to outwit something or rather.I hope this will be of use to some people and reassure others that having Honey Fungus is not the end of the world.As I have said,I have it everywhere in my garden and you can deal with it,If I think of anything else ,I will post.Happy gardening.....by the way,I use roundup everywhere in the garden,except near the vegetables ofcourse,have done so for years,and have a huge worm population ,carpets of bluebells and wood anemonies,and every kind of fern,fungi and wildlife you can think of,.....if it is harming anything,I honestly can't find any sign of it.....when it comes to the vegetables,I use no chemicals and next to no digging.

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    1. Thanks Rhoda for some of your stories! It is good to get the experiences of someone at the harder end of the problem where you have a particularly susceptable site - poor drainage, Summer dry and old woodland. Your experiences are very interesting and informative and I admire your philosophical attitude.
      You raise a lot of interesting points particularly the one about not damaging bark by strimming and other activities. I have often thought not digging also helps by not damaging vulnerable roots - perhaps counter intuitive as it also chops up the bootlaces.
      Your mention of it liking plastic mulches reminds of my own story in the post about the plastic pond liner.
      You sound to have an acid soil if enkianthus does well! Although I have argued that popular opinion over-exagerates the dangers of armillaria the published lists of susceptable and resistant plants are quite accurate, perhaps you could be bolder in your choices of new planting material. (not that your successes with japanese maples is not bold!)
      I am sorry you might have had difficulties in getting your comments through. When I make long comments on other sites I do it by typing it on a document and copying and pasting it onto the blog. I can try again that way or even change it if I have said something silly.

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    2. You can also press 'reply' if you want to add something as I do now!
      Having reread your first contribution of course you have an acid soil and do seem bold in your planting. Having an acid soil does not inhibit one from trying none acid lovers.

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  12. Hi Roger, I found your blog very interesting but while I am sure you do have Armillaria in your garden the mushrooms you have photographed are not Armillaria. They look more like Hypholoma, possible Hypholoma sublateritium. Species of Hypholoma often colonise the same log or stump that host Armillaria species.

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  13. Greetings to New Zealand!
    I can see from the authority of your fine blog that you are right. Thanks very much for the correction. I would be grateful to hear if I have any other mycological errors you will alert me!

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