Hugelkultur -- good wood, bad (allelopathic) wood

In the dozens of hugelkultur threads, crucial information about toxic woods that should not be used is often burried by the quantity of it all.

So let's restrict this thread to the discussion of woods that are likely to be problematic.

In coastal B. C. Our worst offender is cedar. It takes forever to rot and it prevents many other plants from sprouting. In the east black walnut and black locust are known to adversely affect other plants.

Please list the worst offenders in your region. If there is a comprehensive list somewhere, please direct us to it. Thank you, Dale

I was just about to post this in another thread (How to kill Siberian Elm and Tree of Heaven), but this info will go better here.

This week I removed a large Ailanthus (Tree of Heaven)that was growing close to the house. It kept sending suckers that grew very rapidly.

I read in that other thread that Tree of Heaven is allelopathic, so I googled more info and found this article regarding Allelopathic and Herbicidal Effects of Ailanthus:

http://www.jstor.org/pss/2444812

“Mature trees of Ailanthus altissima produce one or more potent inhibitors of seed germination and seedling growth. Inhibitor activity is highest in bark, especially of roots, intermediate in leaflets, and low in wood…The inhibitor(s) from Ailanthus root bark exhibited strong herbicidal effects when sprayed pre- and postemergence on plants in soil in the greenhouse. Postemergence effects were striking, with nearly complete mortality of all species, except velvetleaf, at even the lowest doses tested. The results suggest the allelochemical(s) from Ailanthus may have potential for development as natural-product herbicides.”

This probably explains why the tree I planted is still really small even though I planted it about 8 years ago and it’s supposed to be a relatively fast grower. Below is a photo of my sad little 8 year old Austrian pine. The big tree behind the block wall is the Tree of Heaven.

These trees grow rampant here in the southwest, don’t know about other parts of the country.

I've been putting aged juniper logs in the bottom of my buried wood beds. So far, no visible problems. Our soil here is somewhat alkaline clay.

I see Arizona cypress in another thread. I think it's safe to say that Cypress,Redwood, Sequoia,and all of the cedars can harm garden soil. Most of what North Americans call Cedar are actually members of the Cypress family.

Broadly speaking, coniferous trees are more problematic than are broad leafed ones. They often have aromatic oils. If it keeps moths at bay it may have a similar effect on seedlings.--- If it's a prefered wood for shingles or fence posts, chances are it will be slow to break down and may prevent growth of desirable plants.

Wood that has been chemically preserved should be considered toxic.

Bad: California Pepper tree. two species are commonly called California Pepper tree. The Peruvian and the Brazilian Pepper tree. Both are allelopathic. After a couple of years of composting/decomposing, they should be okay. I don't know if they would be okay as for example the bottom layer of a 6' or 8' Hugelbed. does anybody know when wood is allelopathic, how far the grow inhibiting property reaches? Needs to be next to it, a foot away, 2 yards?

Osage orange takes forever to rot. We have fence posts on our place that are approaching 100 years old that were cut from Osage orange by my grandfather.

imo its all a matter of what you plant, and how long your willing to wait for decomposition to plant other things. there is no bad wood. i use cedar, juniper and pine for my gooseberry hugel beds. they LOVE that stuff, and will be 10x more productive than other woods. better flavor, bigger berries, higher yield. currants also do very well in them.

things that take a long time to rot are a different story, osage orange, black locust, etc... its more of a waiting game at that point. but chances are you have more trees around than just those type of woods. and those woods are far better used in other ways.

Willow, they will sprout a new tree from small bits in the soil. When we had our housefire we had to put in a new raised drainfield and our contractor dug us a pond and used the topsoil for fill around our drainfield and house, we were pulling willow roots and shoots out of it for a couple of years..there was a lot of other wood and sod and stuff buried in those backfill areas which made really wonderful garden soil, they will grow anything, just about.

wet willow will root, dry willow wont. same with wet acacia branches will root, dry wont. the devil is in the details, each wood needs to be used according to its properties. or at least putting some initial thought into it helps.

my dad had cut my mom a willow branch to use to prop up her clothesline..she used it all summer and fall and in the winter she left it outside propping up the clothesline...it sprouted in the spring, was dry and wasn't even planted..just sitting on the ground and propping up the clothesline..she ended up keeping the willow and moving the clothesline..that was more than 60 years ago and is still at that house

hubert cumberdale wrote: i use cedar, juniper and pine for my gooseberry hugel beds. they LOVE that stuff, and will be 10x more productive than other woods. better flavor, bigger berries, higher yield. currants also do very well in them.

I'll keep that in mind for areas where I might want to try acid-loving plants.

I'm very wary of willow. (say that ten times fast ). Broadleaf maple is notorious for re-growing from stumps. That's great for my coppice production but I'll make sure that any big maple stumps are dead before they are burried.

My beds will make for a good case study on re-growth characteristics for the wet Pacific coast. I have piled up somewhere between 150 and 250 cubic meters of wood waste, stumps and all. 95% of these trees were living cottonwood, alder and maple between 2 and 8 inches in diameter. That's enough to fill 15 dump trucks.

All were cut in late fall when root systems have plenty of stored energy ready to feed spring growth. I did this on the wetter areas of the property. I cut somewhere around 5000 young trees. So my bet is that I'll have thousands of sprouting stumps and that many trunks will take root.

Anyone care to bet against me.

acidic woods for acid-lovers (berry bushes) , hardwoods for all else...
I'm using maple, oak, and birch currently for a hugel bed.

Has anyone used white pine or Virginia pine? I have tons of them that we've been chipping up until I found out about hugelkultur...

I read in the other Hugelkulture thread someone saying "don't use conifers". Well we're surrounded by them here, and it's a bit depressing to think I can't use all those Douglas Fir logs we have piled up and rotting. If they've been outside for two years do you think they'd be okay? What about the cedar? I think we have a few scraps in the log pile and at this point I doubt I could tell them apart from the fir. I would not use fresh cedar, but if it has been out in the elements for a year or two?

We do have Red Alder and Bigleaf Maple around but I don't think we have enough to make an entire bed. Doug Fir grows like a weed around here so it's in plentiful supply.

The Fir will rot although it will hog nitrogen for some time. The Cedar will rot slowly and may prevent certain plants from thriving. I'm sure that if you let all the neighbors know that you want branches you'll have a never ending supply. The going rate for wood disposal in your area is $50 per ton. You may have to take it for free or for very cheap if you are off the main road. "Used Cowichan Valley" is bound to have landscapers who need to dump tree waste. Davey Tree is always looking to unload chips. Ask for a load without much cedar.

Mariah Wallener wrote: I would not use fresh cedar, but if it has been out in the elements for a year or two?

I'm using juniper (what we call "cedar" here) aged a couple years; so far, no problems.

How about mycelial colonized conifers, would they still be considered N hogs and/or acid forming?

my dad had cut my mom a willow branch to use to prop up her clothesline..she used it all summer and fall and in the winter she left it outside propping up the clothesline...it sprouted in the spring, was dry and wasn't even planted..just sitting on the ground and propping up the clothesline..she ended up keeping the willow and moving the clothesline..that was more than 60 years ago and is still at that house

chances are it rooted at the base of the stem where it was set on the ground, even if the rest of the branch died off. I would call that dieback rather than drying. the whole branch has to be bone dry. when i take big willow cuttings to establish instant trees, sometimes they die back all the way to the base the way you described. others dont and you can have a 10ft willow tree fast.

i like to use willow for other uses though, coppice, baskets, wattle fencing, etc... willow rots REAL fast when its finally dry. so it doesn't make for a long term hugel bed. if its all you got though i wouldn't be opposed to using it.

cool to hear that tree is still there, its a survivor.

Potato, pototto --- A branch that appeared dead grew again. Good reason to be careful about willow and make damn sure it's dead. Willow bio-char is unlikely to sprout.

The widening of my 5/8 mile long lane has produced mountains of maple, alder and cottonwood.

I buggered up the order of the photos. The first one shows how it looks after some pruning. The archway is tall enough drive a dump truck under. The second photo is the before shot.

I'm wary of anyone who blanketly says there's good and bad wood.

Different woods may have different effects, but that can be an advantage for some purposes.

What about layering manure in the gaps if you are concerned about nitrogen use?

Or applying a thicker layer of soil on top, or using the reportedly alleopathic species very far down in the lower realms of the hugelkultur where their primary function for a long time might be water retention or wicking from below?

I am looking for good science or experiments comparing those who say you can use chips or small branches vs the folks who say the benefits increase dramatically with large chunks of wood. Some difference might be accounted for simply in the total wood volume of a solid large chunk vs the air space in chips, the packing density could vary a lot.

I think a lot of the facination with bigger wood has to do with trying to make beds that will last a long time without having to be rebuilt. This is something that doesn't concern me at all. I want my beds to break down. The quicker the better. There's an endless supply of wood waste available both on farm and off and as it breaks down it will make good soil. I'm charging for wood disposal so quick breakdown frees up space for further cash flow.

Beds can always be topped up. They don't have to be completely re-done just because some wood has rotted. If I determine that a bed has become wood poor, I can always load the finished soil onto a truck and dump it where needed or it could be clawed to the edges so that a new base could be dumped in. So far I have about 30 man hours into my 150+ cubic yard beds. Properly equiped the construction of hugel beds doesn't need to be a Hurculean struggle.

Back to Good Wood , Bad Wood --- For me there are definately good and bad woods for my purposes. A good wood for me to put into the soil must firstly be wood that I don't want to use for some higher purpose.--- Cedar logs have value for me for framing any outdoor structure since it is by far my most rot resistant wood. Douglas fir is the strongest and most valuable construction wood on my place. I would never toss a good fir log into a grow bed. Gary oak is something that fetches $10 per board foot for the best boards. The scraps make great firewood. So only bark and rotten stuff will go to the beds. ----- There are massive quantities of quick rotting maple, cottonwood and alder available. Much of it is low grade stuff with no market value. This stuff is not alleopathic, so for me it's good wood. Any useful cedar , fir, or oak trees are bad wood for my Hugelkulturs and cedar is bad period since I'm not willing to risk problems when I have such an abundant supply of rotty stuff.

Cedar Rotting --- I shingled a roof from a cedar that had been lying dead on the forest floor for more than a century. There was surface rot with bushes and ferns living there going 10 inches deep but no roots penetrated the heartwood. To me this made this tree good wood for cedar shakes and bad wood for gardening. Second growth cedar is not nearly so rot resistant.

I certainly get what Dale is saying about higher uses for solid wood, that's always been an elephant in the room for me on this topic when I hear of whole logs used for example.

There does seem to be these 2 approaches using the word Hugelkultur:
There's the folks that say what makes it work GREAT is the trench to collect moisture, and the solid big wood to wick it up again, with the composting of the wood being secondary.
And then there's the folks that say "use anything" and basically treat it like a soil covered woody compost pile, and see the rotting as a key component.

I'd still like to see any systematic study/comparison of the two approaches.

Links anyone?

Lacia Lynne Bailey wrote:
I'd still like to see any systematic study/comparison of the two approaches.

Looks like a great project for someone who would like to see such a study.

I got called out to look at this glorious mess today. There are enough cedar slabs to fill 15 or 20 demolition bins. If these slabs were fir, maple or alder , they could go to a facility that uses wood waste in bagged soil mixes. Instead the disposal cost will be several thousand dollars higher. The smell is so strong that I got a head ache. There are almost no weeds surrounding the place which indicates that something is suppresssing their growth.The sun and rain combo really brings out the oils. --------------------------- Later the next day --- I got the job and am holding a firewood free for all, as a means of cleanig this up. Some ads and phone calls have led to about 30 people who want it for firewood, raised bed building, fencing etc. It's going to be a "Gong Show" as every firewood hound in Victoria scrambles for the best pickings

I was considering making a hugelkutur bed with some mulberry limbs and branches I cut down when I pollarded the tree earlier this winter but had someone suggest that perhaps Mulberry like willow might sprout and then root. Any thoughts on if this is likely or not?

Has anyone gone to firewood suppliers to source their logs to start their hugelkultur beds with? Of course it doesn't make sense to pay regular firewood prices, but I'm thinking these suppliers would have an amount of partially rotted or mis-shaped material that they'd be happy to dispose of at a discount.

Most yards have mounds of rotten cores, saw dust and most of all bark. I like hardwood sawmill slabs because of the speed of rot and because slabs have a disproportionate quantity of nutrient rich bark. When large firewood blocks are split they often shed bark. Older salvaged windfall sometimes sheds all of the bark when split. This stuff is easy to find because firewood guys advertise.

I'm pursuing a multi-pronged strategy to obtain hardwood bark. 1. Offer a good deal on yard clean up so I can get paid to collect what I need.

2. Leave a trailer or truck on site where the mill or firewood guy can toss bark and rotten stuff.

3. Offer my place for firewood guys to dump their bark and rotten wood. This one requires some policing since some firewood types are also in the garbage business. Only a select few will be offered this service.

Has anyone used Doug fir in their bed? I work at a mill and I can have as much as I can cut and load for free. Just curious if I should look somewhere else for more success or just use what is available. Both options seem to have a place in permaculture. Thanks!

I put 17 big fir stumps under a mound of soil 16 years ago. This was done for 2 reasons.

1.Avoid having to burn or otherwise dispose of the stumps.

2. Provide a base for a rock garden beside a small pond. The stumps were piled first and then the pond was excavated and the soil dumped on the stumps. We named it "Jasmine Mountain" after my youngest daughter. I have since learned that it is Hugelkultur.

Fir stumps take a long time to break down. After 10 years in a wet environment, my stumps had protruding chunks that could have been burned firewood.This can be good or bad. I would scrounge some Alder, Maple , or Cottonwood to plunk on top. then you'll have some quick rotting in the beginning.

Thanks Dale. Good idea to supplement the top with a different type of wood. I talked to a local power company about letting them drop off a load of wood chips from their tree trimmings. I was thinking about putting that on top as it will be a variety of different wood in small pieces. I will try to post some pictures when I get started. Thanks again.

Over the years I have come to know and love poplar. It roots readily from cuttings, grows quickly, coppices well, dries well for firewood and biochar, and rots quickly for hugelkultur. Poplar sucks up a *lot* of water. It's not the "best" wood available for any of these attributes, but it's good at all of them.

Poplar has what I like to call a high exchange rate. I've dealt with poplar and fir slabs. If two similar slabs are left out in a good, all day rain, the fir slab may be dampened 1/8 inch deep while the poplar slab doubles in weight as it sucks up the rain falling on it as well as absorbing water from the damp ground.

When drying out, poplar quickly wicks water from its core in response to surface evaporation.

So any water locked up in a poplar log is more available.

I don't have an acute water shortage, so there is no reason for it to be in long term, less available storage. All I need is a giant sponge that can react quickly to water supply and demand. Poplar serves that need.

I have thought of making a small pond and filling it with the wood and water before putting the wood into the bed. I thought this would be a good way to saturate the wood before I put it into the bed and under some soil. I have also thought about collecting some driftwood from a couple of nearby lakes. Just curious if this is something that has been tried before?

Wet wood makes for heavy lifting.

The most persistent driftwood are rot resistant species. Some of the best hard woods sink. Conifers float.

I was wondering if anyone has had any experience using eastern hemlock in a hugelkultur? I was thinking of planting blueberries on it and was wondering if anyone knew if it was allelopathic or rot resistant. I have read that it is not good for shingles or outdoor use, which leads me to believe that it will rot just fine.

One thing cedar in a bed is good for growing is Red Huckleberry. If you walk in the woods of the northwest, you'll probably notice that Red Huckleberry is usually growing on a rotting cedar stump or log.

Dear All,

Does anyone have any experience using Aspen that they could share?

I have two big ones that came down, and am about to fire up the chain saw to make some raised hugulkultur beds.

Should I be using them for this purpose?

Thanks,

R

I posted a separate thread about this, but not much of a response, so I thought this would be a good place to try.

Is sassafras allelopathic? I've heard that it is in one place, but it was a scholarly article, so I would tend to trust it. Has anyone ever used sassafras in hugelkultur with success or detriment?

I will be putting hugel-swales on slope this year . We had an ice storm 3 years ago that felled many trees. The damaged ones continue to fall. So I have plenty to choose from - I just ask my neighbors for the dead rotted stumps and branches and they gladly give them to their goofy neighbor. There is plenty of BlackWalnut here and I will say many things grow with it. In the woods Oaks ,Maples , Poplar , Beech , Redbud , Sassafras , ETC. Ferns , greenbriar, dogrose , blackberry , wild grape. My house garden is just beyond the canopy of some old walnuts, on a slope. We cut into walnut roots in the garden sometimes and the leaves blow and walnuts roll into it and compost. Always a bumper crop of tomatos , beans , herbs , greens, arkansas black apple . I have read that the juglone decomposes in 2-3 months. I wonder in a hugel bed with the wood in large pieces how long it will stay active?Anyway - I will try to stick with other hardwoods , but if the walnut gets into a bed , or as top dressing I won,t lose any sleep over it.