Posted: 11/05/2014 at 09:07
Sounds like you grew a variety of hypericum....calycinum....and this will take over.
Geraniums like rozanne (blue flowers all summer), Ann Folkhard (lovely yellowish leaves with magenta flowers), Wargrave Pink (pink) are all tough, spreading (not invasive) colourful and easy. There are varieties with coloured foliage like Pink Ice.
Campanulas like Portenschlagiana ....already mentioned today in another thread.....provides blue flowers over a long period.
Helianthemums.....sun roses.....are evergreen summer flowering plants with white, pink, red, yellow or orange flowers. Quick growing.
osteospermums provide white, pink or purple flowers and flower forever.
Ground cover can also be provided by shrubs and taller perennials too.