I've been toying around with the idea of a hugel bed that uses coppiced trees to replenish the wood content... forever.

I'd plant nitrogen-fixing trees like alder every so many feet, and coppice them every few years. They'd self-prune their root system when cut, leaving the roots to rot in the soil. And as a bonus, I get wood from the coppicing.

I only chose alder because I know it's a nitrogen fixer that coppices nicely. I hear the catkins are barely edible though. Anyone know of a more palatable legume tree that'll coppice well? Zone 5/6

What does the Permies clan think?

attached it a sketch

black locust is known for this. Osage orange is also a classic choice and also makes a living fence.

I thought black locust pod was toxic, does honey locust work? Didn't know locust would coppice.

Lots of trees will coppice. Hazelnuts is one you can also eat. Mulberry. I guess if you coppice you might not eat as much.

Hybrid poplar grows really fast and apparently you can propagate it from cuttings really easily. Fast growing, low btu firewood.

Those aren't legumes.

Not sure if alder is a good choice for food. We have lots of them here and we never even considered trying. Some people say they don't coppice too well, while others say it does. Great pioneer tree though. Also good for growing shiitake/oysters.

Ok we'll if you also want edible, try seaberry. Only thin I'm not sure of its coppicing value but it fits your bill otherwise.

I use our local strain of red mapel sort of like that but I can see where a nitrogen fixer or food producer would be a better choice. Mine were small saplings which were growing naturally on the property when we bought the place and I moved them to the front yard thinking they must survive well. They did but were always thin, spindly things until I started chopping their heads off to make them more bushy. Now that I'm trying to build up the soil in that area for growing fruit trees or other food crops I'd hate to remove these mapels because they do provide material for char and other things.

Matthew McCoul wrote:I've been toying around with the idea of a hugel bed that uses coppiced trees to replenish the wood content... forever.
I'd plant nitrogen-fixing trees like alder every so many feet, and coppice them every few years. They'd self-prune their root system when cut, leaving the roots to rot in the soil. And as a bonus, I get wood from the coppicing.
I only chose alder because I know it's a nitrogen fixer that coppices nicely. I hear the catkins are barely edible though. Anyone know of a more palatable legume tree that'll coppice well? Zone 5/6
What does the Permies clan think?

Couple of thoughts. There is some debate if planting trees on hugels is a good idea. Also, I'm not sure if N-fixing trees is necessary because part of the reason d'etre of an HK is to store water and nutrients. Also, if I did go with an N-fixer, I'd use a productive one like seaberry, gumi, siberian pea shrub, honey locust.

I'm not sure what you mean about replenishing the wood though. If you keep adding wood you'd need to keep covering with soil and eventually they'd be Paul Wheaton sized - or taller. I could be misunderstanding you though...

Cj Verde wrote:

Matthew McCoul wrote:I've been toying around with the idea of a hugel bed that uses coppiced trees to replenish the wood content... forever.
I'd plant nitrogen-fixing trees like alder every so many feet, and coppice them every few years. They'd self-prune their root system when cut, leaving the roots to rot in the soil. And as a bonus, I get wood from the coppicing.
I only chose alder because I know it's a nitrogen fixer that coppices nicely. I hear the catkins are barely edible though. Anyone know of a more palatable legume tree that'll coppice well? Zone 5/6
What does the Permies clan think?

Couple of thoughts. There is some debate if planting trees on hugels is a good idea. Also, I'm not sure if N-fixing trees is necessary because part of the reason d'etre of an HK is to store water and nutrients. Also, if I did go with an N-fixer, I'd use a productive one like seaberry, gumi, siberian pea shrub, honey locust.

I'm not sure what you mean about replenishing the wood though. If you keep adding wood you'd need to keep covering with soil and eventually they'd be Paul Wheaton sized - or taller. I could be misunderstanding you though...

About replenishing the wood, I won't be, the trees will be.

The idea came to me from geoff lawton's soil video, where he mentions that as you prune a tree, the tree also severs parts of it's roots.
By that, idea, if i coppice the top of the tree, the tree should shed much of it's root stock underground, leaving root wood inside to rot.

A coppiced tree also rapidly regrows it's removed biomass to regain that balance so I wonder how much available material would be left for anything else. My guess is that the tree would reabsorb whatever was lost to the soil and that removed biomass (from the coppicing) would be lost to the system. Unless it is added back, of course, in some form. That's where being a nitrogen fixer might help. It comes from the air with the carbon dioxide so there is gain to the system there. I'm just thinking through my keyboard. My answer is I don't know but it's interesting to consider. My produced biochar gets mixed with compost, rabbit manure and other inputs and added back to the soil.

Matthew, sounds like a cool experiment, I like the innovation. Let us know how it turns out!

What's the goal of the hugelkultur?

I have cut several thousand red alder in the range of 3 to 7 inches diameter. Very few have made an attempt to regrow. Mine are cut at the ground. When cut at 6 ft tall, many will sprout branches. If these trees are allowed to mature, they are prone to center rot and can split in two or shed branches. These can hit you or your perennials. The roots get into everything. I like alder as a perennial cover crop on property large enough to be able to spare the space for a decade. I have it growing at a distance from the garden. The leaves blow in. I rake up great soil beneath them and use it in the garden. This doesn't seem to hurt alder. It's a pioneering species that can live on pure gravel.

Dale Hodgins wrote:It's a pioneering species that can live on pure gravel.

Yeah, that's a good point. That's why I was wondering the purpose of the HK.

Cj Verde wrote:

Dale Hodgins wrote:It's a pioneering species that can live on pure gravel.

Yeah, that's a good point. That's why I was wondering the purpose of the HK.

The hugel has 3 main purposes to me

First - A garden bed resistant to both flooding and drought.

Second - A way to bring soil life and fertility to our compact, overfarmed clay soil. Before we bought the land a decade+ ago, it had been commercial soy/corn for many years. We've done much to improve the soil, but not in the area i plan to put the hugel bed.

Third - experimentation. I'm doing a 90 foot bed, divided into 9 different sections, and taking notes on each.

the main overarching goal is to make a garden that is largely self-sufficient, sustainable, and regenerative and to chronicle thay garden.

Matthew McCoul wrote:
First - A garden bed resistant to both flooding and drought.

This first one is a little problematic - I think. The N-Fixing part is good but you're limiting yourself to what can grow in semi-shade and not compete with the tree roots. I think there are plenty of productive N-fixing trees and shrubs I don't see the benefit to Alder specifically.

Good luck & keep us posted.

Lots of great info so far.

As it sits, my revised plan is to use seaberry or honey locust for added food production, and i'll be trying this on 3/9 sections in the 90ft bed.

Combining ideas from different threads, forums, coversations, looks like it's going to be in 10 foot sections:

Sect 1. wood, soil
Sect 2. char, wood, soil
Sect 3. char, soil

Sect 4. wood, straw, soil
Sect 5. char, wood, straw, soil
Sect 6. char, straw, soil

Sect 7. wood, soil w/coppice tree
Sect 8. char, wood, soil w/coppice tree
Sect 9. char, soil w/coppice tree

Then I'm going to keep a journal on how it all turns out.
Started work on it yesterday, it's going to be a long project.
Anyone with more input, please feel free to add and thanks for everything do far!

With that much space you may want to consider Siberian Pea Shrubs again as Cj Verde mentioned. They have edible seeds, don't need a lot of water, and are quite nice because they lack thorns. They also don't grow so large that they would shade other plants too much. They are quite dispersive in their immediate vicinity through the sheer quantity of [edible] seed they produce.

Matthew McCoul wrote:...seaberry or honey locust for added food production...

Seaberry is good but very thorny. You need a male & female. You can cut branches and place them over like an umbrella to protect other plants.

You might want to keep the honey locust or any tree coppiced or pollarded so it doesn't grow too tall. I don't think I've heard this mentioned before but it you grow tall trees on an HK I would think that they'd have a tendency to fall over like trees at the edge of a pond.