It's best to put some in every year.

For my 1/4 neighborhood pond, I try to put in the 3-5 clumps of three trees each.

The decay process hits the smallest limbs first and then on down until you have the trunk and some nubs of the larger branches.


Excerpt from Robert Crais' "The Monkey's Raincoat:"
"She took another microscopic bite of her sandwich, then pushed it away. Maybe she absorbed nutrients from her surroundings."