Yesterday, I emptied out one of my 10 gal containers where I grew peppers, putting 4 plants per/container. I have a couple dozen of these, so filling them with potting soil is a major expense, so I recycle all I can and am constantly trying to find less expensive fill material.

This spring I tried filling the bottom third of the containers with pine bark, raked up around the firewood pile. So all different sizes, some pieces bigger than my hand, some the size of marbles.

When I emptied the container, the bark was just laced with pepper roots, they obviously found something there they liked. Many of the bigger pieces were now soft enough that I could break them up with my hands.