Made my first hugel bed mid last Summer. Used several types of wood I could find for the tiny bed.
Among the wood was an Eastern Red Mulbery Log about 4-6 inches thick that I had pruned off of one of my father-in-law's trees. It was laying on a neighbor's fence. Anyways, I let one end of the log hang out of the end of the bed because I was to lazy to cut it again and figured it would add more of that edge effect. By the end of the Summer there were about 6... 1ft long twigs growing out of that log.
I have been wanting a mulberry tree and now one is showing up for free... but in the middle of the garden sadly. I am thinking I will let those spikes stay in bush form and keep it low/small. Then occationally cut one off and stick it in the ground somewhere else to get a new tree started. I am betting that would work for several types of trees. Giving the birds something else to eat besides my other fruits elsewhere in the yard... and focusing their fertilizer and insect eating into my garden.
As a bonus I also had some field mice move in and dig a tunnel under the log. I even saw once where they took a large tomatoe and roll it across the yard and could not fit it into their hole. So the mice were increasing the airflow under the ground for benificial soil life and bringing in even more fertilizer from around the yard. I am hoping some bumble bees move in next year too.