I've got a raised bed along the side of my yard, built with those "Windsor" wall stones that have a little lip on the back. The bed is built up against the neighbor's not-very-attractive retaining wall (it was chosen for decoration, not function...and it really does look lovely). The yard slopes up as the wall goes along, so the beginning of the wall is 3-4 stones in height, and eventually there are no stones at all, as the ground rises to meet the top of the wall.

Anyway...I filled the bed with a mix that was too high in organic matter, so the soil has started to sink. Because of that, I'm faced with the prospect of digging everything out and replanting in the Spring (no mean feat -- it's a perennial herb bed!).

So..while I'm replanting, I'm considering raising the bed by one more row of stones, since we hit ground before we got to the back of the yard. Of course, this means that I'm going to need more soil.

I have no extra soil in my yard (I live in the city, the yard is small), but what I do have is rocks...lots of them. Our yard is on top of a shale bed, and we've pulled out zillions of small stones as we've been digging various beds. This is the reason for my neighbor's aforementioned retaining wall -- she raised her entire yard so that she could have a garden.

My question is...as I re-dig the bed and raise it again, can I put some of these rocks back into the bottom of the bed, to add some volume back in? How deep would they need to be, if that matters? What percentage of rocks-to-soil would be OK at what depths? Etc. etc. If I can use some of these rocks, that will solve two problems -- it will give me something to do with the rocks, and I won't have to buy as much soil to fill the bed.

Thanks!

new soil or any medium in a raised bed will settle, and will need topping up along the regardless of how much organic matter was in it. sounds like a lot of work digging all out that is there just to put stones in the bottom?

we always tamp our medium down a bit when we first make a bed and even then the medium is layed higher than what is initially needed, this helps negate that settling to a degree, then what we do continualy is use a good layer of a green type hay mulch which breaks down and adds not only nutrients but height to the medium.

where we have to we just lay in our case more mushroom compost to bring the level up.

so maybe in your case just add more medium on top?

len

I would start topping off with a mix of something that has a considerable mineral fraction in it, like sand or very fine gravel, Turface ...... My raised bed soil is a combination of pine bark, reed/sedge peat, sand, Turface, and compost/composted manure, and it is FULL of life - extremely productive.

The larger the organic fraction, the greater the shrinkage. Using conifer bark as your organic component will slow the breakdown of the organic fraction considerably. Each year, you can top off with a mix of bark/sand/Turface/other mineral amendment and soon your shrinkage will be minimized. 75-80% mineral and 20-25% organic is still a highly organic RB soil.

Al

Al