The Walden Effect: Farming, simple living, permaculture, and invention.

Sweet potato cover crop

Box turtle in sweet potatoes

People throw around the term "symbiosis" all the time, but most don't realize that the word only means that two (or more) organisms are living close together, not that they're helping each other out.  Symbiotic relationships can be parasitic (one organism benefits and the other is harmed), commensalistic (one organism benefits and the other is neutral), or mutualistic (both organisms benefit).

Why should you care?  If you're a permaculturalist trying to build guilds or an organic gardener experimenting with companion planting, it's handy to know where your combinations sit on the mutualism-to-parasitism spectrum.  That way you can grade the interactions --- parasitism is probably a failure, commensalism is a moderate success, and mutualism is the holy grail of the guild world.

Sweet potato cover crop

While my sweet-potato cover-crop experiment is closer to a commensalism than a mutualism, I'm so happy with the results that I'm going to deem it a glowing success.  This spring, I set out sweet potato slips into some beds I've developed just past the root zone of a peach and an apple in the forest garden, and the sweet potatoes thrived.  They soon formed a living mulch beneath the trees, but only barely rooted there, so they didn't steal any nutrients.  When harvest time came this week, I discovered huge, beautiful tubers, and the tops of the sweet potatoes created a deep mulch ring around each tree, perfect for taking the trees into winter.  Meanwhile, the bare ground left behind in the sweet potato beds made it easy to sprinkle oat seeds for even more biomass production.

What would turn this symbiosis from a commensalism to a mutualism?  If the sweet potatoes had done better close to the trees than they would have done in a vegetable garden bed.  I'd be curious to hear if you've developed any true mutualisms in your garden, but in the meantime, I whole-heartedly recommend sweet-potato cover crops for anyone needing to build biomass around fruit trees.

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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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I love how happy that box turtle looks (to me, anyway)! She made my morning. I love when you post wildlife picutres. :)
Comment by Emily from Bristol Thu Sep 12 09:50:46 2013
Emily --- Stay tuned --- there's a closeup of Ms. Box Turtle to come in tomorrow's post. :-)
Comment by anna Thu Sep 12 12:41:24 2013
First, thank you for your blog. I'm slowly making my way through the archive and learning a lot. The study of permaculture is fascinating to me. Currently I'm reading "Paradise Lot - Two Plant Geeks, One-Tenth of an Acre" by Eric Toensmeier. It's an amazing story and you might find it helpful in your quest. By the way, how did you keep the deer from eating your sweet potato vines? I have to grow mine behind a fence.
Comment by Karen Thu Sep 12 14:24:49 2013

Karen --- I read and enjoyed Paradise Lot. You can see my review here (and don't miss the search box in the sidebar, which makes it easy to find reviews of books you're wondering if I've read! :-) )

We have a fence all the way around our perimeter now, which is how we manage to grow sweet potatoes despite serious deer pressure. I think the crop is close to their favorite!

Comment by anna Thu Sep 12 16:13:29 2013
Good article. Why don't you join us in North American Fruit Explorers and Southern Fruit Fellowship?
Comment by Anonymous Thu Sep 12 21:49:48 2013
As far as symbiosis... I think the same thing when some of my trees are being ravaged by tent worms. If the trees survive, which they usually do, they grow stronger with more shoots. Nature always has a way of correcting itself.
Comment by Leah Thu Sep 12 23:07:33 2013
We don't have fruit trees yet. So how about justing adding the biomass to the compost pile? I don't have enough food scraps coming from the house for the amount of browns I have, so I'm thinking this is ok. I'm in the SW corner of Ohio by the way ;)
Comment by Lisa Siegmann Sat Mar 25 19:12:47 2023
...should work great! I hope you'll report back and let us know how it goes.
Comment by anna Mon Mar 27 13:43:31 2023

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