We have 40-50 palm logs on our property in northern italy..Is it possible to make a hugelkultur with the logs in front of a 1 meter high retaining wall? We also have stone,
good quality dirt and clean rubble. Is it possible that this could serve as extra support in front of the wall? We would like to make a tomatoe garden on top after it is made.

Is it possible that this could serve as extra support in front of the wall? 

Support for what?  The wall?  Is it leaning?  I would not consider hugulkultur as a structural support for anything as it breaks down and shrinks as the wood decomposes... if that was what you were meaning.

We have 40-50 palm logs on our property in northern italy

  That's a great score of wood!  I'm not sure of the characteristics of Palm wood, but I have not heard of any reason not to use palm wood so I think that you are not going to have any problems with growing in a hugulkultur made of palm.  The only thing to consider is how long it takes to rot, which I don't know, because I don't know palm.  It may not be as productive in the first year as in the following few years, until the wood gets breaking down.  If the materials that you have for mounding over your wood are separated, choose the most organic rich stuff for the surface or the small areas that you are planning to place tomato plants.  When making the mound wet the wood as much as you can but dampen all other material, rather than soaking it.  I can see no reason why it wont work, particularly in the long haul.

Yes , indeed a great score but alot of responcibility to make a final resting home.
The terraine here is sloping from high mountain down to the lake so there are many levels of retaining landscapes ( Lake Como)
The retaining wall is showing signs of bulging so I take your point on the fact that a hugelkultur does minimize over time...good point ..
I think the solution is to first build a structural stone wall in front of the existing 1 meter high wall which supports 3 magnificent cedar trees and then make a hugelkultur in front of the new structure.
ThankYou for your information and will continue to investigate the process.
Kind Regards
Linda

The retaining wall is showing signs of bulging so I take your point on the fact that a hugelkultur does minimize over time...good point .. 

  Somebody must have made an error when constructing it.  Some of the types of walls that you describe have been in use in the Mediterranean for centuries.  The cedars might be pushing it with their roots, or have increased the hydrology (bringing water retention/reducing draingage) that is pushing on it.  Without seeing it, I should say that you may be able to take apart the existing wall where it is bulging and rebuild it properly.  Otherwise yes, probably a good idea to build the whole thing. some good stone building advice here

Welcome to Permies, by the way!

I think the solution is to first build a structural stone wall in front of the existing 1 meter high wall which supports 3 magnificent cedar trees and then make a hugelkultur in front of the new structure. 

If you do this, then your slope will have extra support.  You could fill in with rocks and dirt between the two walls and maybe have a small shelf for planting something.

Do you have any photos to share?

Agreed..back to the draing board and thanks for the article on proper stone wall building.
I sent this to dengarden:
Thankyou for your insights on the proper way to make a stone wall.
I am surrounded by stone walls here in Italy and need to replace a 1.5 meter tall retainer way because of poor drainage and improper concrete decorative made on top of the stone.
I believe this decorative technique of simulating tree branche and bark in cement dated back to 40s or 50s. It has a similar look to the architecture of Gaudi.
I plan to remove the building cement to be able to access the stone work behind.
This retention wall is only 1.5 meters high and 8-10 meters long and supports three massive cedar trees above.
The rooting system is also applying pressure to the wall.
I am able to send photos if you dont mind having a look.
Your comments would be invaluable..
Grazie Mille!
Saluti,
Linda Rosewall

I've used palm tree trunks to build a hugelkulture.  They work fantastic.  The wood of a palm tree is so different from most other trees.  It's fiber-y and strong.  You can cut through it easily with a sawzall (which is what I used to cut down 6 huge queen palms, rather than my chainsaw).  As it begins to decay, it's tremendously spongy and absorbent --- which is exactly what you want in your hugel. 

I deliberately inoculated my palm logs with mushrooms by drilling holes and smushing a mix of wild mushrooms and compost into them.  If I were to do it today, I'd still drill the holes, but I'd make a slurry of wild mushrooms, a bit of oatmeal (to feed the fungi) and fresh rainwater ---- blend it up in the blender, and then just pour the slurry into the holes.  Much easier that way.

The only drawback is that your hugel will deteriorate much much quicker than one built with hardwoods.  I didn't mind that.  The soil that has come from those old palm trunks is rich, black and beautiful. 

Even better (from my perspective) is the web of roots left in the ground once you cut palm trees down.  As you probably have realized, palm trees have a massive web of smaller roots, as they normally grow in poor sandy soil.  The root mass helps them cling to the sand when big storms blow.  My soil is heavy clay, but the trees rooted out as they normally would in sand, leaving me with a thick mass of roots in the top foot of the soil profile.  Once I cut those trees down, I noticed mushrooms coming up throughout that area.  I've planted apricots and a cherimoya in that space, and those new trees are thriving in the fungal network established among those old palm roots.

Marco, grazie Mille per tutto !
I really appreciate your comments on palm logs.
Will let you know how it goes.
Linda