Hello I have area probably 6-7yard long against my patio fence. I am thinking to plant some nice perennial in a fall some that will bloom next year summer to spring.
The soil of that area is not very great. Mostly it is loom that out there 4 years ago. I believe should prep the soil now if I am will be planting in October. What are the suggestions for how to prep the soil?? Please also advise how should I choose the plants?

I have some perennial already in the pots.
1- Bugbane
2-Garden phlox ( white flame)
3-Echinacea ( 3) hot coral , Wild berry
4- Astibe Delf Lace
5- Ajuga reptans’ Burgandy Glow’

And please would someone tell me why my Echinacea flowers petals are bit down?