My most recently made hugelkultur swale beds were made almost entirely of freshly cut river birch and sweet gum. I don't yet know how well it'll work compared with already rotting wood, but I can give you an update this time next year.
Adding alfalfa pellets seems like a great idea, if a bit expensive. The sacks are around $12 here.
I grow inoculated legumes which makes a huge difference, in my opinion.
