Shallow rooted perennials for pots

[TiddleTaddleTat]

Just picked up 7 terracotta pots of approx 18cm diameter and about 7cm deep.
Any ideas what I could grow in these with such a shallow root area?

Alpines possibly.

Succulents - houseleeks etc.

Hardy geraniums are fairly shallow rooted.

Thanks - I've got mountains of houseleeks and sedum already but got started with those.
Have had a go with oregano... we'll see.
Anything with flowers? Trailing would be lovely

Erigeron (Mexican fleabane)? Mine is in a pot like that in the centre of an outdoor table.
Little iris and muscari bulbs in one?

Creeping thyme, miniature Dianthus species (Cheddar Pink and the like), small Erodium (storksbill), bonsai tree - I have a very nice mountain ash in a pot about that size, and it produces flowers and berries each year. Sisyrinchium - there's a deep yellow variety and a deep blue variety only a few inches high.

Crocus?

Oregano hot 'n' spicy is shallow rooted, it will spread across the pot and hang over the edge. Gorgeous purple flowers in the summer. It's evergreen too.

Thank you ! Lots of ideas here. I got the pots for free (from a skip!) they're a lovely shape and look homemade so I'll try and make good use of them