My hugelkultures are primarily filled with pine both rotted and fresh (I use a combo). They do fine! I grow lettuce, spinach, strawberries, kale, broccoli, flowers, borage, tomatoes, herbs, peppers, onions and much more on them and everyone of them has done well. I toss partially composted material from the
compost heap in some of the holes and this may help it break down quicker. I use pine because that is what I have an abundance of.