2018 Update: There's More Than One Way to Use a Tree Stump
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There's a big stump from the cottonwood left in the middle of an old flower bed. I remembered your radio show's episode on Hügelkultur and went back to read the article on it at your A to Z archives. That specific question was about a tree that had fallen, but I only have the stump left. Once it gets decaying (I'm thinking about introducing edible mushrooms to accelerate this), can I "Hügelkultur" the stump and grow some shade loving perennials in that bed?
---- Britt in Grand Rapids
A. Well, first I have to point out that her location allows Britt to grow the type of blueberries the recent article she mentions focused on: the tiny but flavorful native lowbush varieties that exist naturally in the Northern US and Canada. The fruits are small but pack quite a flavor punch. And our favorite advisor on the medicinal properties of plants, the late great Dr. Jim Duke would add that such a native, uncultivated variety should have the highest concentration of beneficial phytonutrients per gram.
And Dr. Duke's research for the USDA found that blueberries in general might be the single healthiest thing you can eat—especially for prevention of dementia. So grow lots of 'em!
Now, there are many ways you can use that stump, and growing 'shrooms is number one. A quick check of mushroom growing sites reveals that cottonwoods (a type of poplar) are one of the best woods for growing some of THE most desirable mushrooms.
Specifically, that stump can be inoculated with the spore of two different types of oyster mushrooms—pearl and blue oyster—and the edible mushroom known as turkey tail, although the oysters will grow better in a Northern climate.
And the time to get started is now. You order what's called 'plug spawn' of the desired mushroom variety, drill holes in the stump, drop in the plugs, brush the stump lightly with melted beeswax and then keep it shaded and moist. (Britt says that her area is naturally shady, but if your personal stump happens to be sunny, use shade cloth or a big beach umbrella to block the sun.)
There's also another intriguing mycelial possibility: Morels! It turns out that cottonwoods are a good host for everybody's favorite wild mushroom. But you shouldn't try and grow more than one species on a single stump or log, so Britt will have to choose. (Although if morels begin to appear naturally, the choice will be made by nature.)
And then is Hügelkultur in her future?
Depends on how much they like oyster mushrooms (or morels) and how well they grow on the stump. If the mushrooms flourish, I would just dedicate that area to 'shrooming.
But if the oysters are not Rockefellerian, we drop back to the stump advice I've been delivering for decades, which is kind of lazy Hügelkultur. Frame out the area around the stump, score the top surface of the stump with a chain saw to speed its decomposition, and then fill the frame—which should ideally be about six inches taller than the stump—with your native soil and plant what you want over top.
If the plants seem a little slow to grow, amend the soil with small amounts of composted horse or poultry manure, corn gluten meal or other fertilizer that's naturally high in Nitrogen. (Because the decaying wood might suck up all your nitrogen on its way to becoming soil…) Or just grow plants that don't need a lot of nitrogen the first couple of years.
Now I want to share a bit more of Britt's wonderful email. She continues: "I also wanted you to know about the 'experimental' crop I'm planning for this year. When I was picking out my seeds, I saw that the company sold artichoke seeds, and that they're annuals in my USDA zone six! I always try to get something new and 'weird' to try out every season. It doesn't always work out, but it's like buying a lottery ticket: it's fun to dream."
Britt closes with "Please let me know if you're ever in the Grand Rapids area—you can come out and see one of my team's roller derby games."
Ha—I'll bet she's a jammer!