I have a corner of my growbed with no board behind the felt. I used a scrap board that was roughly the right size though missing a corner. I extended the felt past the missing section down into the trough. The yellow line in the picture marks the edge of the board under the felt. The ivy that is planted right at the edge is growing much less vigorously than the other ivy of the same type planted at the same time. It’s getting enough water, so it may be short on roots. I’ll keep an eye on it and see how it goes.
In the circle, out in no man’s land I’ve pinned the leaf of a beach oleander (weed in Hawaii, exotic plant to us here in the cool damp NW). I picked it up off the floor when I moved the parent plant out of the house for the summer. The leaf had a new plant starting and I’m not one to waste plants. We’ll watch and see what happens.