Thursday, July 7, 2011


I have grown many mushroom logs over the years and, like any good composter, hate to throw them away when they are spent. It is still a good source of carbon and minerals and not to be wasted. I usually chop them up roughly and throw them in the compost bin, where they tumble for some time, very slowly getting smaller. When I redo one of the containers in my garden, I find I am often short on soil (due in large part to my dislike of store-bought potting soil), so I throw a chunk or two of the decomposing log into the bottom of the pot to fill space. I figure the log will slowly decompose over several years time. During that time, it will feed the soil and provide a reservoir of nutrients.

Recently, I came upon a method of soil-building called hugelkultur. The basic premise is that decaying wood harbors a great diversity of life. If you see a fallen log in the forest, it is covered with different organisms. The older the wood, the more life there is. So, according to hugelkultur, when building soil, you bury wood in the soil. The wood provides both shelter and food source for a wide variety of life. Over the course of several years, the wood will break down into a rich soil that is full of organic matter and many nutrients.

When a mushroom log is good and spent, the interior is spongy and soft. They are easily chopped up into smaller chunks with a large knife. When putting together a new pot full of soil, I like to put a layer of well-draining material on the bottom, like sand or rocks, and then a layer of roughly chopped spent mushroom logs on top of that. I mix it in well with some good compost and then make sure I have three to six inches of dirt on top of the wood. This gives new plants plenty of room to spread their roots without running into wood immediately. While a plant can push its roots through mostly rotted wood, it may have difficulty with some of the harder portions or if you use fresher wood.

Thus far, I have only found two difficulties with hugelkultur. The first is that rotting wood is low in nitrogen. This means that your soil will most likely be low in nitrogen, too, so other sources, such as blood meal, compost, and nitrogen-fixing plants are a good idea as your soil matures, especially if you are going to be growing plants that need lots of nitrogen, like fruits and vegetables.

The second problem is that wood is high in carbon, which mostly gets converted to carbon dioxide as it decomposes. This is good for your plants, providing a slow, steady supply right where they need it. However, that carbon all takes up space. This means that the level of your soil will slowly drop as time passes, sometimes by several inches. This is great for annual plants, as it gives you lots of room to add compost. However, it can be bad for perennials as they slowly get buried in the compost you have to add.

Overall, though, I really like it as a method for bulking up soil in a new bed or container. I especially recommend it for mushroom growers, like me, who have lots of spent logs laying around that they don’t want to throw away.


  1. I've also been bothered by the long period of time that Hugelkultur wants before beds become fully productive, and, it seems to me, that it makes a good, "permacultury" progression to prepare the bed, and then deliberately and liberally infest it with Mushroom mycelium. If the Mushroom species we choose provides a useful harvest to us along the way, so much the better...

    To that end I have recently been busy culturing-up a bunch of Shiitake spawn, and gathering logs. Luckily it's Winter and we've had some great storms, so plenty of fallen trees around for fresh, clean logs.

    Very happy to see that there someone else out there with similar nutty ideas to mine ;-)

  2. Mike - Shiitakes are good for growing on logs above ground (they are primary decomposers), but I doubt they would work well completely buried. I like to do the shiitakes (oyster mushrooms mostly in my case) above ground and then use a secondary or tertiary decomposer for the hukelkultur phase. King stropharia (Stropharia rugoso-anulata) or shaggy manes (Coprinus comatus) would be good, though king stropharia won't grow outside in my area. I am hoping to get them going in my future greenhouse, though.

    I agree, it is nice to find people with similar ideas. It is a big part of why I started this blog.

  3. Ah - to clarify - I wasn't planning to bury the logs for the initial (Mushroom) phase - only afterwards. I'll probably try Button mushrooms for the next part. Shaggy Manes are a great idea - they often show up near the gate to my veggie garden, if I can catch them in time.

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  5. Fantastic idea - I use wood and some leaf litter to fill the bottom of the pot - even a few bits of broken pots. Like your blog, very creative and thorough.

  6. in regards to your first difficulty with hugelkultur... the soil rich in carbonaceous materials will not necessarily be lacking nitrogen as long as there is a diverse and healthy population of beneficial microorganisms there to fix nitrogen from the atmosphere and provide it to the plants. i was informed of this by bob connard of green string farms, in petaluma, california.

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