Best to still do your homework though and look up any plants you pick from that RHS list. I've just looked at it and it mentions Erigeron karvinskianus which from my experience would not be happy planted on a clay soil. But it also mentions Astrantia which definitely would.
Clay soil - Cheshire/Derbyshire border. I play with plants and soil and sometimes it's successful
@NewGardenerCornwall I have similar conditions and found that a Hot Lips Salvia plant loved the clay soil and didn't stop flowering until November. It was a harsh snowstorm with minus degrees Celsius that killed the Hot Lips Salvia at the end. Another plant that survived without issues was a yellow flowering Eysimum plant.
If the stone is porous and the water does drain away, then you should be able to plant quite a few things. I was under the impression it wasn't draining at all through winter Ground covering plants like Ajuga and Iberis will be fine in shallow soil, and don't mind wetter conditions in winter, or drier in summer - within reason. You may find that some small daffs, crocus and Convallaria [lily of the valley] would also manage. You'll probably need to experiment a bit. For taller plants, the aforementioned Crocosmia would probably be fine, possibly some of the smaller Asters, and some of the smaller, variegated Carexes would as well. They don't have huge root systems. Even some Euphorbias would manage. Shrubs would still struggle with such a small amount of soil for roots though.
It would help if you could post some photos of the area to help give a better idea of the size of the space.
It's a place where beautiful isn't enough of a word....
I live in west central Scotland - not where that photo is...
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I play with plants and soil and sometimes it's successful
I have similar conditions and found that a Hot Lips Salvia plant loved the clay soil and didn't stop flowering until November. It was a harsh snowstorm with minus degrees Celsius that killed the Hot Lips Salvia at the end. Another plant that survived without issues was a yellow flowering Eysimum plant.
I ♥ my garden.
Ground covering plants like Ajuga and Iberis will be fine in shallow soil, and don't mind wetter conditions in winter, or drier in summer - within reason. You may find that some small daffs, crocus and Convallaria [lily of the valley] would also manage. You'll probably need to experiment a bit. For taller plants, the aforementioned Crocosmia would probably be fine, possibly some of the smaller Asters, and some of the smaller, variegated Carexes would as well. They don't have huge root systems. Even some Euphorbias would manage.
Shrubs would still struggle with such a small amount of soil for roots though.
It would help if you could post some photos of the area to help give a better idea of the size of the space.
I live in west central Scotland - not where that photo is...