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Inky cap mushrooms in the garden

Young inky capIf you've got cute, little mushrooms popping out of your straw mulch, chances are you've grown inky caps.  The aptly named inky cap mushrooms dissolve into a mass of black goo as they mature.

Inky cap goo

Inky cap mushroomsScientists think that the life history of these mushrooms is a way of spreading their spores more efficiently, and recent evidence suggests that various unrelated mushrooms have come up with the same trick through convergent evolution.  Older books lump them all into one "genus" --- Coprinus --- and I'm not enough of a mushroom expert to tell you which of the newly split off genera my species is actually a member of.

I'm also disappointed to discover that there doesn't seem to be much information out there about how inky caps fit into the garden ecosystem.  The fungi are decomposers, working hard to break your straw down into compost, so I guess that makes them beneficial (unless you were hoping not to have to refresh the mulch this summer.)  But I can't find any information on whether inky cap inoculated straw is beneficial or harmful to garden plants in any other way.  Any ideas?

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About us: Anna Hess and Mark Hamilton spent over a decade living self-sufficiently in the mountains of Virginia before moving north to start over from scratch in the foothills of Ohio. They've experimented with permaculture, no-till gardening, trailersteading, home-based microbusinesses and much more, writing about their adventures in both blogs and books.

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My guess is that it works both ways with the inky cap family. Gardens normally benefit from mycellium forming breaking down waste, forming complex networks, and delivering nutrients. However, when a inky cap dies it can kill nearby plants. Even edible inky caps like shaggy mane will eventually go to black mode when they age causing all the nearby plants will fall over.

Love your blog.


Comment by Mikey Sklar Sun Mar 13 10:25:47 2011
Fascinating tidbit. Are you sure it's true? I can't seem to find anything on the internet about the black goo killing plants (although I did just find one reference that shaggy inky caps kill a few nematodes.) Are you speaking from personal experience? How could you tell it was the mushroom killing the plants? Which specific plants were affected?
Comment by anna Sun Mar 13 10:47:39 2011

This site has a personal account of dead shaggy mane killing a herb garden:

Another site describing lawns being killed by fairy rings, but with a overall statement about mycelia being a good thing for your yard and rarely a cause for concern.

Comment by Mikey Sklar Sun Mar 13 14:31:15 2011
Thanks for the followup! That's just what I wanted to know. It's a fascinating anecdote, but I'm not sure I buy it. With the amount of inky caps that end up in gardens on mulching straw, I can't imagine they are so dangerous to plants or there'd be more stories like that around. On the other hand, the inky cap species people find in straw are rarely shaggy caps, so maybe shaggy caps really do kill plants but the inky caps that grow in the garden don't. I'll have to keep my ears open for more stories!
Comment by anna Sun Mar 13 18:21:13 2011

Thanks for putting me on the right trail to finding out what mushrooms I had photographed. The inky-caps are so varied, it's no wonder I had trouble figuring it out, but yours are clearly just like mine so that was a great help. Thanks!

Comment by Laurie Marie Photography Mon May 2 16:18:10 2011
I'm glad I could help.
Comment by anna Mon May 2 16:48:00 2011
Are Inky Cap Mushrooms hallucinogenic or can I fry them up with some steak?
Comment by Dusty Sat Oct 1 05:51:33 2011

There are several different species, so I hesitate to give you any information on the inky caps you might have in your yard. If I were you, I'd get two good edible mushroom books and make sure what you think you have matches the description in both books, then read what the books say about edibility.

I've never eaten them, but have heard that at least one species is edible, but that it reacts badly with alcohol in your body, so you shouldn't eat it if you've had any alcoholic beverages lately.

Comment by anna Sat Oct 1 10:35:28 2011
I can say without an absolute doubt these things have completely killed my plants in the garden I just started. I wasn't having this issue until I bought more dirt from lowes (Kellogg's organic garden soil). These things grow 4"-8" overnight and sometimes if I don't catch them in time I come home to the remnents (deflated stems and black goo all over the area). These have killed every seed that was growing to the point where I have to clear out the dirt and start fresh. I got the ink on the top of my hand when picking them out and the tops of my hands are also covered in a bumpy rash now. These are garden killers, end of story.
Comment by Megan D Mon Jun 29 12:10:27 2015

This is my first attempt at the straw bale garden and my first year of going organic. My plants started out doing great, until my first inky caps appeared. I had bought some Black Velvet mushroom compost from Lowe's and applied it around my young seedlings to help them become established. When I first found the Inky Caps, I found maybe 6 or 7 and ripped them out, straw and all, and threw them away. All the researching I did said they were okay and not to worry, because it just meant I had a lot of organic matter in my straw bales. Well, a month later and I have inky caps coming up in 10 - 40+ at a time, two to four times a day, right around base of plants. When the caps come up or fall on a plant, wherever it is touching the plant, that part of the plant withers and dies. It is non selective at to what the plant may be. I've lost numerous tomatoes, peppers, cantaloupes, squash, etc. I have never seen anything grow as fast as these things do. I have tried to pull them out, cover with newspaper and cardboard, but to no avail. They grew to full maturity under the cardboard and newspaper. I have since read that since they are a fungus, I can try a fungicide to try and get rid of them. I am at a loss of what to do, other than try an organic fungicide. I'm not at all happy with the Black Velvet mushroom compost from Lowe's. It would have been nice to know this may happen, if applied to a garden area, before finding out the hard way. I have this compost all over the tops of my straw bales, with no way of getting it off. I can't replant, because they are so numerous and fast growing. They would just kill any new plants I put in there. Very discouraged right now. I just hope I can find a remedy, before I lose my whole garden to these invasive, plant killing, Inky Cap Mushrooms!! If anyone can help me with this, I would be very grateful. God bless an I hope you have a great gardening day!

Comment by Natoshka Wed Jul 1 14:06:21 2015

My apologies to Black Cow & Lowe's. I have found out the inky caps did not come from any item from Lowe's. They came from the straw bales I had purchased for my Strawbale Garden. After purchasing more bales, I had set them out to condition them, but never applied any compost, fertilizer, nor anything else to them. It has been raining nearly every day, for the past two weeks. Yesterday I noticed inky caps coming from under the coverings I had on them. So, I knew I had to come back and repost the truth. I have also noticed all the bales are full of chiggers! Thank God for Diatomaceous Earth! Of course, I do stand firm that, in my garden, these "Inky Cap Mushrooms" killed every plant they touched with their tops!

Comment by Natoshka Mon Sep 7 13:41:10 2015
You mentioned thank God for DE,why? Does DE kill the inkys? This is my fifth year of straw bale gardening and have never had inkys that won't stop growing and killing everything. Please help.
Comment by Jackie Ludwig Wed Jun 20 21:40:33 2018
Are these INKY CAPS POISONOUS OR TOXIC TO SKIN? I found several of them growing in my onion and chamomile and I removed them with my hands. The black goo got all over my fingers. Should I worry? Please help!
Comment by Emmy Hulse Sun Jun 16 09:41:03 2019
Looking at the comment about the compost I am thinking I did not get them until I put out Black Kow the are everywhere! I have not put down straw yet, so it is not that. Anyone have a remedy for them?
Comment by Robbie D Fri Apr 10 00:15:15 2020
I had these pop up in a grass fertilizer we put down in the spring. We never had them before, so I attribute their growth to whatever was in the fertilizer - assuming that they grew on the material, not that spores were in the fertilizer itself. They did not kill my grass, and I picked them without irritation to my skin. I made ink out of them to use for painting. I hope they come back!
Comment by Anonymous Sun Jul 18 12:43:34 2021
I'm in New Zealand and have been doing haybale gardening for the last couple of years. While these inky caps have always come up, I've never had as many this year. I usually just pulled them out but not knowing what they were I left them alone this year and even watered them in :( now there even popping up in my seed rows and must be disturbing my seeds. Should I just remove all haybales and start again? Is there a safe way to treat haybales before starting next garden. We use haybales here because straw is too expensive. Any help gladly accepted. It parson sowing time and now I'm late :(
Comment by NzGardener Sat Feb 5 14:03:48 2022
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