Permabed Construction

I ordered my wife Zach's new book for Christmas and we've loved it, especially the pictures! As an engineer I want to make sure I understand the construction of them, specific to the outer trench. Zach recommends to dig a 12" wide by 6" trench around the border that doubles as a foot path. This seems like a great idea as it would also double as a water holding feature (kind of like a micro swale/moat) if filled with wood chips, gravel, or other media. Which got me to wondering about the orientation in the landscape; if planning a row of multiple permabeds is there a significant benefit from being installed on contour, or am I over analyzing this?

I also wanted to ask if there are any pros or cons to laying down a layer of small to medium size branches when initially digging the bed and mixing in the compost, kind of like a micro hugelkultur feature. Love to hear thoughts on this idea.

I noticed this is your first post. I would like to extend a formal welcome to you! We’re glad you’re here!
When you say “permabed” do you mean hugelkultur or some other kind of traditional raised bed? For me it wouldn’t matter. I’ve found everything is better on contour. There are others here that are way more experienced than me when it comes to hugel construction. Maybe they’ll notice this and give us some advice.
I may need a bit wider path than 12” but it sounds awesome. I need to look up the book. I love the steadiness of gravel but I’ve most often used wood chips for my paths. Most of my gardens are big tree guilds and I like to keep the fungi happy. You mentioned laying down small limbs at the base of the bed. I’m not exactly clear on that one.
Anyway, it’s always great to see someone new around. The more people catch the Permie-bug the better for everyone!

Here is an example of a Permabed. There is also a youtube that Zach did.


Source

I would be interested in knowing more about the "Ecosystem Core".  I didn't look at the youtube so maybe it is explained there.

Thanks Anne! Give me a few days and I’ll probably be making one.

John Doyle wrote:I ordered my wife Zach's new book for Christmas and we've loved it, especially the pictures! As an engineer I want to make sure I understand the construction of them, specific to the outer trench. Zach recommends to dig a 12" wide by 6" trench around the border that doubles as a foot path. This seems like a great idea as it would also double as a water holding feature (kind of like a micro swale/moat) if filled with wood chips, gravel, or other media. Which got me to wondering about the orientation in the landscape; if planning a row of multiple permabeds is there a significant benefit from being installed on contour, or am I over analyzing this?

I also wanted to ask if there are any pros or cons to laying down a layer of small to medium size branches when initially digging the bed and mixing in the compost, kind of like a micro hugelkultur feature. Love to hear thoughts on this idea.

On contour is definitely the way to go for water holding, but consider where the water will go if you get a major rainfall event. This will possibly indicate a need to design an overflow spot so that when your uppermost swale fills up, it has somewhere to overflow into your next swale without blowing out a hole in your hugelbed or flooding some other area in an unplanned and possibly catastrophic way. Ideally, swale 1 fills and overflows through a gap (level with the top of the swale) you've constructed (perhaps armoured with rock to eliminate erosion) into swale 2. When swale 2 fills, it overflows in turn - this overflow is offset from the first one so the water doesn't run fast in a straight line down the hill, but proceeds slowly downhill in a zig zag fashion filling each swale in succession.

On the question about including branches of different sizes, I think there is benefit to doing this so decomposition of the woody material proceeds at different rates.

Good point Andrea. I’ve started anchoring my small contour beds with perennials. Sometimes rocks, then Mediterranean herbs that don’t like wet feet.

Thanks for the tip Anne. I found his stuff on YouTube.

Hello again John. I found his video series on YouTube and have some thoughts. He said compost or other amendments could be added to the permabed. The area I live is world famous for pottery. Your thoughts on adding wood to the base are spot on for me. I don’t think I would try it any other way. So I guess it’s dependent on your native soil composition.