The ground is shale and dense clay here on a mountainside, so my small herb,
lettuce and rhubarb garden lives in an 8' x 16' raised bed. Along one of the
16' sides, my husband dug out a 3'-wide strip - not a raised bed, but into
the ground - for a perennial border, which is doing quite nicely the past
four years, except at the bottom end. The ground slopes just enough that
heavy rain accumulates at the low end. The perc rate of this soil is very
slow, so the clay/mud wall at the end of the bed is backing up the water and
killing the plants at that end. So far, a Hylotelephium "Autumn Joy" (fka
Sedum) and a little mound of dianthus rotted out and failed to re-emerge. At
the top end and the middle of the bed everything's fine, with coreopsis,
astilbe, columbine, dianthus, lamb's ears, hyacinths, species tulips and
peonies coming back and proliferating.
We're not going to do more digging in this area. Later in the season,
nasturtiums and four o'clocks are quite happy at the wet end. But I'd like
to have a perennial or two at the wet end that come out on their own, and
survive, so the bed doesn't look so lopsided in the early spring.
So far, I thought of digging up some of the Virginia bluebells and bloodroot
plants that I have at woods' edge (they prosper, even in areas where the
water stands after a heavy rain) and installing them there. Any other ideas
of something that might survive these advense conditions? The bed gets about
3 hours of direct sun in the morning, then dappled light the rest of the
day. Zone 6.