Joseph I would reccommend to read the whole thread to understand fully. For example cedar is widely accepted as bad wood, but someone reported he had very good results with red huckleberry, gooseberry etc.
I was planning to make a different type of list, but decided not. There are some web pages attending the subject
tcperma ;
appropedia ;
ourochre and more in permies. Meanwhile Jordan Lowery made a good point in that thread while they were discussing whether there is a real distinction, and I think it deserves to be mentioned at this post also:
"in my opinion it's all a matter of what you plant, and how long you 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 flavour, 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... it's 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."
So yeah it depends on your purpose. If you want your hugel bed to be productive a century after you built it (sarcastic smile here), osange orange might be the only good wood :) But a list doesn't hurt anyone.
But generally speaking:
1- Rotten or softer stuff (like alder, poplar) goes near the surface, while "maybe" or slower rotting stuff goes into the core of a hugelbed. You may include limited amount of allopathic wood deep in the core without any ill effect.
2-Trees suitable for pollarding might cause problems -sprouting. Maybe.
3- Using only a single type of wood, will cause the bed to have too much of a character. Poplar-hugels will rot fast (4-5 years) but will act like a giant sponge, while cedar-hugels will not rot initially (8-10 years min). You might want to mix different types of woods to take the edge of.
4-Introduced species may act like they are "bad wood", while they are "good guys" in their native range, and this cannot be blamed on the wood itself. Since the environment lacks specialized decomposers (especially fungi) adopted to deal with tannins, oils and allopathic compounds, decomposing process may linger, and these compounds will have a negative impact on hugels. (While I was raking through the web, I came across numerous conflicting feedbacks on some species - eucalyptus, pines, oaks and somewhat bamboo. When I dig in, I realized that there is a overlap with native-introduced range with this problem. This is expressed also in one of the comments in one hugelkultur article at permulturenews.com. Unfortunately, it introduces subjectivity to the list, so I neglected negative feedbacks from introduced ranges. House-plants and other exotic plants might decompose slower as well).
5- There are many uses for "bad woods". They are sought after for their rot resistance and dense wood properties. They might have a higher purpose.
6- You might want to exclude diseased wood if you don't know how contagious it is (especially from monoculture production areas - olive). Some diseases, such as fire blight, might escape. Meanwhile you should not forget that burying is probably the oldest way to get rid of all kinds of nasty stuff, so similarly hugel beds will effectively lock and kill slowly most diseases (of plants). Only 5% or maybe even less of diseases might be an issue. Burying deeper or other techniques (biochar) might be solutions.
7- I couldn't find it where I saw it, but someone claimed that spring cut trees with all that water and energy stored and being programmed to leaf out, are more prone sprouting, while winter cut trees lack water, so they struggle to sprout. Currently I am experimenting something similar with poplar and pale: spring cut poplar and pale is sprouting like crazy, winter cut not so much. So, I think it is a valid point, but I wouldn't rely on.
8- There are thousands of species of trees out there. The list doesn't include all of them. Observe the nature, search the web if you know the name, or just do it and report back your results :).
Here is a short list of good wood/bad wood.
Good wood:
-birch
-alder (fast rotter)
-milkweth (arttic)
-cottonwood (acts like a giant sponge)
-willow (a 1000% dead willow is good, 99% not so much... Willow is well known to sprout as it is a zombie plant, extreme caution here!)
-mulberry (might sprout)
-sycamore
-maple
-douglas fir (or you can use it for construction)
-poplar (acts like a giant sponge, fast rotter)
-apple
-juniper (some reported very favourable results)
-fir
-plane (might sprout)
-oaks (perfect for hugels, but you can also grow shitake mushrooms)
-pine (there is a general discussion about this, depends on the species, where you are located and your purpose me thinks.)
-spruce
-aspen
-ash
-cherry (not black cherry)
-buckeye
-green snake wood (condalia viridis)
-buckthorn (maybe)
-Palm (outer trunk might resist to rot. There are positive reports from florida)
-para rubber tree
-bamboo
Bad wood:
-cedar (rot resistant. Second growth or fast growth are less rot resistant. Some had good results with cedar, with red huckleberry, gooseberry)
-black walnut (emits an allopath called hydrojuglore (??), wood is valuable and south after, blackberry and wild grape is immune to its allopathic character)
-black locust
-ailanthus or tree of heaven (allopathic)
-arizona cypress
-redwood
-sequoia
-california pepper tree (allopathic)
-osange orange (takes ages to rot)
-black cherry (emits a allopath called amygdaline (??), wood is valuable and south after)
-china berry tree
-catalpa tree (?)
-fuchsial (sprouts very strongly)
-himalaya berry (don't use it when green, it will definitely sprout, good when dead. Or goats love it)
-salmon berry (will sprout)
-english ivy (zombie plant)
-mesquite (has a higher purpose, very dense wood, perfect for fuel wood)
-olive (olive has allopathic properties. I used it in one of my hugels, and it didn't perform very well for over two years. Maybe its allopathic character dies of in a year or two. Also most olive trees are treated with -cides. Caution!)