| This isn't a rock garden question but I'm not sure where else to post this, and maybe somebody here has dealt with a similar issue--
My yard is long and narrow, on a fairly steep slope that was terraced with landscape timbers by a previous owner. The timbers are 20+ years old, rotting and beginning to sag and fail. I will need to rebuild the retaining walls within a couple of years, and I'm leaning towards using interlocking concrete blocks as a do-it-yourself project. Most of the retaining walls are low, about 24", with the highest one about 36" tall.
Here's my question: I would like to have ferns and other small shade-loving plants growing on the wall so rather than setting the stones tightly against each other, and with the recommended gravel and landscape fabric behind it for drainage and soil retention, can I use just soil and leave gaps between the blocks where I can plug in plants? Since the walls are fairly low and the terraces will be heavily planted I think I might be able to get away with this, without worrying too much about the walls failing or soil washing out.
Has anybody tried anything similar? BTW here's a photo of my yard, taken in December when the retaining walls are most visible:
And here's a view of the garden in summer:
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